College Entrance Examination Reviewer in Science, Exercises of Environmental science

Download College Entrance Examination Reviewer in Science and more Exercises Environmental science in PDF only on Docsity! SCIENCE REVIEWER Definitions of Science General Science % An organized body of knowledge gathered over a long period of time to explain the world we live in. % Knowledge or a system covering general truths or the operation of general laws especially as obtained and tested through scientific method. Scientific Method Gathering Preliminary data Formulating a hypothesis* Testing of the hypothesis Analysis and Interpretation of data Drawing of Conclusion OARWON> Identifying the problem (Questioning) Independent Variable — variable changed by the experimenter Dependent Variable — variable that responds to the variable that is changed in the experiment. Experimental group — groups that receive treatment. Control group — opposite of Experimental. % hypothesis — it is what we think the answer to the question is and it should stated in terms of the variables defined. Laws and Theories *Scientific law — a description of a natural occurrence that has been observed many times. “Scientific theory — a reasonable explanation of a scientific law. It is derived from a hypothesis that has been supported by repeated testing. “Model — helps visualize occurrences and objects that cannot be observed directly. Note: Scientific lavs and theories cannot be proven absolutely. They are maintained as all observations support them. Measurements % In science, the metric system is used in all measurements for its convenience and simplicity. % The International System of Units (SI) uses the seven base quantities and units given below: Physical Quantity Unit Name (symbol) Mass Kilogram, kg Length Meter, m Time Second, s Amount of Substance Mole, mol Temperature Kelvin, K Electric current Ampere, A Luminous intensity Candela, cd A. Reading Metric Measurements No. of significant digits = no. of certain digits + one certain digit (0 or 5) Example 1: The diagram below is a metric ruler used to measure the length of a pencil. How long is the pencil? } a | | | 8 cm 9 10 The smallest fra centimet 2 metric ruler is 0.1 cm. This corresponds to the last certain digit in any measurement. The pointer reads 9.0 cm. One uncertain digit should be added. In this case it is 0. Answer: Length of pencil = 9.00 cm B. Converting Metric Units Conversion of metric units is easily performed, Mega ‘108 Decimal point Kilo 10 moves to the left Deka 10? Hector 10° Base unit 10° Deci 107 Centi 10% ‘sve tothe Milli 10° right Micro 10° Example 2: How many grams are there in 37.d centigrams? %& To convert 37.5 cg to grams, count the number of steps from centi to base unit. Since it moves upward, the movement of the decimal point is to the left. Answer: 0.375 g Major Regions of the Earth Lithosphere — the solid part and the largest portion of the earth Hydrosphere — the liquid part. It covers about 71% of the earth’s surface Atmosphere — the gaseous portion that envelops the earth Biosphere — the region where living things are found. RONS Rocks and Minerals Everywhere you look, you find rocks of different shapes and sizes. What is important to remember about rocks is the way they were formed. The varying conditions for the rock formation influence the characteristics that each rock develops, %& Igneous rocks — formed from hardened magma and lava. e.g. Rhyolite, Granite, Basalt, etc. % Sedimentary rocks — form from deposited fragments or particles of other rocks that have been weathered and eroded. e.g. limestone, conglomerate, dolomite, shale EXCERCISES FOR GENERAL SCIENCE Match each definition in column B with the correct word in column C. Write the letter of the correct word and the first letter of the correct word in the space provided in column A. A B c 1. A-systematic process of gaining information a. Law 2. Avariable that is changed by the experimenter b. Theory 3. It responds to the variable that is changed in the | c. Scientific experiment method 4. A process that results to the breaking of rocks into smaller | d. Independent pieces variable 5. Process by which infrared radiation from the earth’s surface | e. Dependent is absorbed by water vapor and carbon dioxide in the | variable atmosphere It is a description of a repeatable natural occurrence A reasonable explanation of natural occurrences A sample group that receives a treatment Helps visualize occurrences and objects that cannot be observed directly . An educated guess. . A change in constitution of a rock brought about by pressure and heat within the earth’s crust . Solid earth materials that have a definite chemical composition and molecular structure . A logical conclusion that can be drawn from an observation . This is done to gather important information before designing an experiment. . A periodic rise and fall of ocean water caused by the moon and the sun. . The layer of the atmosphere where we live . Seasonal wind that blows between continent and an ocean . Produced by the cooling and crystallization of molten lava or magma . Process of transporting rock particles f. Weathering g. Igneous rock h. Research i. Troposphere j. Minerals k.monsoon 1. Model m. M etamorphism n. Tide o. Greenhouse effect p. Hypothesis q. Experimental group r. Inference s. Control group t. Conclusion u. Erosion v. Sedimentation w. M etamorphic rocks x. rocks I|.Computation 1. An adult inhales 10 000 L of air a day. What is the equivalent volume in cubic millimeters? 2. One stick of cigarette of a particular brand contains 40 mg tar. If a person smokes 20 cigarette sticks in a day, how many grams of tar does he consume in a week? 3. The nearest star to the sun is 2.52 x 10°? miles away. How far is this in kilometer? IlLEssay 1. What is the difference between revolution and rotation? 2. Unlike earth, which is surrounded by sea of gas, Mercury has no atmosphere. State a possible explanation for the lack of atmosphere in this planet. Biology Biology — the branch of science that deals with the study of living systems and life processes. A. Cells This is probably the most basic term that you would need to know. All living systems are composed of cells. They are the basic unit of structure and fuction in living things. Following is an illustration and concept map of a cell and the different structures contained in it. Cell wall/cell membrane Except for the Cell ———} cytoplasm Except for the! nucleus [|_— protoplasm -—nitochondrion t—chloroplast |__rivosome +—Endoplasmic reticulum t——Golgi apparatus |___lysosome |_centriole [Microtubules and microfilaments Organelles are structures with specific functions found within living cells. % Nucleus — This organelle is arguably the most important structure in the cell because it serves as the control center in which individual functions of the other organelles are coordinated. Cell wall/cell membrane — the cell wall in plant cells and in some monerans and protests provides rigidity for support to the cells and a characteristic shape for functionality and structure. The cell membrane on the other hand is selectively permeable. site where ATPs are abundantly synthesized. algae. %* Ribosome — this serves as the site of protein synthesis. Endoplasmic Reticulum — These organelles serve as channels or passageways through %* Mitochondrion — this organelle is also called as “powerhouse of the cell”. It serves as the ** Chloroplast — this serves as the site of photosynthesis among plants and photosynthetic which materials are transported to the different parts of the cell. Differences between plant and animal cells Centriole — this serves for cytokinetic purposes and is very common among dividing cells Lysosome — the structure is also called “suicidal bag” as it releases digestive juices Golgi apparatus — this serves for selection and packaging of cellular materials. Structure Plants Animals 1. cell wall Present. Absent 2. chloroplast Present Absent 3. centriole Absent Present. 4. lysosome Absent Present 5. vacuole Onellarge Many/small How did the concept of the cell come about? The Cell Theory serves as the basis on which everything that we know about the cell is anchored. There are three elements to this theory; 1. All living things are made up of cells. 2. Cells are the basic unit of structure and function in living systems. 3. All cells come from preexisting cells. Like any biological structure, the cell is composed of biomolecules that are intricately combined to enable the cell to perform its metabolic functions. a. Carbohydrates — immediate source of energy - elemental composition: C,H, O - building blocks: monosaccahrides - e.g. sucrose (table sugar), maltose, amylase b. Fats/Lipids — these molecules serve as another source of energy after carbohydrates - elemental composition: C,H, O - building blocks: fatty acids and a glycerol backbone - e.g. waxes, oils, and cholesterol c. Proteins — these molecules serve as sources of building materials. - elemental composition: C,H, O,N, S - building blocks: amino acids - e.g. amylase, actin and myosin d. Nucleic Acids — these molecules include the RNA’s and the DNA’s - elemental composition: C, H,O,N, P - building blocks: nucleotides Cells according to complexity %& Prokaryotic cells — have no membrane-bound nucleus and organelles; typical of bacteria and blue-green algae % Eukaryotic cells — have membrane-bound nucleus and organelles; typical of protests, fungi, plants, and animals. Cell Transport Passive Transport — does not require the expenditure of energy; moves particles through the concentration gradient. Active transport — requires the expenditure of energy; moves particles against the concentration gradient. Diffusion - this refers to the process in which molecules of solvent move from an area of high concentration to an area of low concentration. Osmosis — this refers to the diffusion of particles or molecules across selectively permeable membrane. Cell Reproduction This refers to the process by which cells divide to produce daughter cells. It involves either mitosis if somatic or body cells are involves or meiosis if germ or sex cells are involved. Mitosis - refers to the division of the somatic cells - also referred to as equational dvision because the ploidy number of the daughter cells is equal to the ploidy number of the dividing cell. The cells in all organisms grow and reproduce by cell division. A unicellular bacterium, after doubling in size, can reproduce by dividing into two cells. In multicellular organisms like man, increase in size is attained by dividing its constituent cells. Gene Segregation and Interaction Dominant Allele - alternative trait that is expressed in the phenotype. Recessive Allele — alternative trait whose expression is marked in the phenotype. Law of Dominance - state that only dominant alleles are expressed in the phenotype and that recessive alleles are masked among hybrids but are manifested among pure breeds. Law of Co-dominance - states that two equally dominant alleles are equally expressed in the phenotype and that no blending is achieved. Law of Incomplete Dominance -— states that among multi-allelic traits, two dominant alleles that are not dominant enough to mask the expression of one another, are incompletely expressed in the phenotype, hence a blended trait is achieved. Mendel’s law may be separated into two rules: first, the law of Independent Segregation of Alleles and second, the Law of Independent Assortment. “Law of Independent Segregation states that the alleles in a gene pair separate cleanly from each other during meiosis. “Law of Independent Assortment states that the alleles of the different genes separate cleanly from each other and randomly combining during meiosis. These laws can be illustrated using monohybrid and dihybrid cross: a. Monohybrid Cross One of the pairs of alternative characters in sweet peas studied by Mendel waqs round vs wrinkled seed. These distinctive characters or traits are called phenotype while the gene or genetic content coding for these traits is the genotype. In example below, both parents are homozygous so that the round (P1) and winkled (P2) parents have the RR and rr genotypes, respectively. The gametes produced after meiosis by P1 is R and by P2 is r so the progeny of the first filial generation (F1) have heterozygous (Rr) genotypes. Since R is dominant over r, then the F1’s have round phenotype. This is an example of complete dominance. R masks the expression of r. This is the dominant allele. The allele that is masked (r ) is the recessive. Female Parent (P1) Male Parent (P2) Phenotype: Round Wrinkled Genotype RR rr Gametes R r Fertilization F1 genotype: Rr Phenotype; Round To demonstrate that the F1’s are heterozygous, a testcross can be conducted wherein the F1 plants are crossed to the homozygous recessive parents (rr). The recessive parent contributes 10 the gametes (r ) while the other parent contributes R and r. Testcross results in 1 Rr (round): 1 rr (wrinkled) or 1:1 segregation ratio. Rr x tr Gametes r R Rr (round) r rr (wrinkled) Genotypic Ratio: 1Rr : der Phenotypic Ratio: 1round : 1 wrinkled b. Dihybrid Cross The members of gene pairs located on different homologous chromosome segregate independently of each other during meiosis. Mendel studied two phenotypes, texture and color of seeds with two alternative traits; round and yellow seeds vs. wrinkled and green seeds. He crossed pure breeding round, yellow seeded plants with pure breeding wrinkled, green seeded plants. The F1 progenies were all yellow round seeded plants. The F2’s gave 315 round, yellow: 101 wrinkled yellow; 108 round, green and 32 wrinkled, green plants. Approximately 9:3:3:1. The method used in getting the genotypic ratio among F2 progeny is called Punnett Square or Checkerboard method. Molecular Basis of Heredity The first part dealt with the physical basis of heredity — the chromosomes. Chromosomes are the carriers of the multitude of genes. Genes or hereditary units, on the other hand, are actually fragments or portions of the deoxyribonucleic acid or DNA. A chromosome is made up of one very long DNA packaged with histones to fit inside a minute nucleus of the cell. Eukaryotic cells with several chromosomes would, therefore, contain more than one molecule of DNA. Prokaryotic cells and viruses generally possess one long molecule of DNA either naked or associated with proteins but not as organized as compared to eukaryotic chromosomes. The DNA has been tagged as the genetic material of all organisms with the exception of some viruses with ribonucleic acid or RNA as their genetic material. Central Dogma of Molecular Biology DNA as the genetic material is capable of transmitting biological information from a parent cell to its daughter cells and, in a broader perspective, from one generation to another. The information stored in its base sequence is copied accurately by replication. Replication is a process of faithfully copying a DNA to produce two DNA molecules identical to the parent DNA. These DNA molecules are then passed on to the daughter cells via the chromosomes during cell division. The information stored in the DNA when expressed will result to a particular trait of an individual. The trait is expressed through the action of proteins either directly or indirectly. The central dogma of molecular biology consists of three general processes namely: replication (DNA synthesis), transcription (RNA synthesis) and translation (protein synthesis). The transfer of information from cell to cell or from generation to generation is achieved by replication. On the other hand, the transfers of information from the DNA to the proteins involve two processes: transcription and translation. Generally, all organisms follow this mode of transfer except for some viruses that undergo reverse transcription. 11 Transcription Translation DNA RNA = —W—____» PROTEIN 4--------- Reverse Transcription Mutation — changes in the genetic materials that are essentially heritable. a. Deletion — refers to a segment of base pairs in the DNA that is spliced off. b. Substitution — refers to a segment of the base pairs in the DNA that is replaced by a different series of base pairs. C. Translocation — refers to segments of base pairs that are differently positioned. d. insertion — refers to base pairs that are added to segment of DNA. Evolution — this process refers to the gradual change in populations through time. D. Animal Development (30 minutes) Animal Cells, Tissues and Tissue Organization Animal tissues are generally classified into four categories: Epithelium, Connective Tissue, Muscle and Nerve. These animal tissues make up all the organ systems of the body. o Epithelium, in its simplest form, is composed of a single continuous layer of cells of the same type covering an extemal or internal surface. o Connective Tissue, has the widest range encompassing the vascular tissue(blood and lymph), CT proper, cartilage and bone. o Muscular tissue consists of elongated cells organized in long units of structures called muscle fibers or muscle cells. The two general categories of muscle, smooth and striated. Striated or skeletal muscle functions for voluntary control while smooth muscle functions for involuntary contractions. o The nerve cells or neurons comprising the nervous tissue each possess a cell body which contains the nucleus and the surrounding cytoplasm. The process come in contact with other nerve cells, or with other effector cells through a point of contact called synapse. Animal Development Animal development is a series of events that is controlled by the genetic information in the nucleus and factors in the cytoplasm. It starts with fertilization and ends into the arrangement of cells which gives the embryo its distinct form. Features which are unique to organism such as the shape of the face, location and number of limbs and arrangement of brain parts are molded by cell movements in response to the action of genes in the nucleus and molecules in the cytoplasm. Stages of Development a. Gametogenesis 12 where organic matter is reduced to simpler substances. Structurally therefore, the ecosystem can composite the following, that is, the abiotic factors; the producers; the macroconsumer; and the decomposers. The abiotic component, on the other hand covers climatic, edaphic (soil) and topographic factors. Climate includes light, temperature, precipitation and wind. Light influences the biotic components in many ways, as in photosynthesis, flowering seed dormancy, leaf senescence, nesting, migration and hibernation. Light quality penetrating with increasing water depths also determines the type of producers (i.e. green algae in shallow water and red algae at greater depths). Temperature affects living organisms by influencing their metabolic processes. It can determine the type of vegetation in different ecosystems depending on its availability. Water as the universal solvent plays an important role in the ecosystem as it serves as a medium for biochemical processes. It can determine the type of vegetation in terrestrial ecosystems depending on its availability. In aquatic ecosystems, however, what plays important roles are salinity, ph, temperature and dissolved oxygen. The atmosphere is a major reservoir of nutrients important to life. Nutrient cycling in the atmosphere is further facilitated by wind. The latter also accelerates evapo-transcription rate causing damage to plant structures. However, it plays an important role in facilitating seed dispersal and in the distribution of plants and animals. Biome - is a geographical unit uniformly affected by a common prevailing climate havin a similar flora and fauna. Terrestrial biomes the world over include: * Tropical rainforests — which have the highest species diversity Coniferous forests — which harbors the pine-trees Deserts — characterized by very low species diversity Grasslands — also variously called savannahs, steppes and scrubs Taigas and Tundras-characterized by permafrosts Aquatic biomes on the other hand include: * Marshlands Lakes Seas and oceans and Estuaries Five Kingdoms Monera — prokaryotic; unicellular; includes the bacteria and the cyanobacteria. Protista — eukaryotic; unicellular/colonial; includes the flagellates, the ciliates, the sarcodines and the algal systems. Fungi — eukaryotic; unicellular (yeasts) and multicellular (molds and mushrooms). Plantae — eukaryotic; multicellular; Animalia — eukaryotic; multicellular; includes the invertebrates and vertebrates. Ecological Relationships a. Mutualism — “give and take” relationship b. Commensalisms- a relationship where the commensal is benefited and the host is neither benefited nor harmed Parasitism — a relationship where the parasite is benefited and the host is harmed Competition — neither organism in this relationship is benefited e. Predation —a relation where the predator is benefited and the prey is harmed 2° 15 Food Chain Three components of a Food Chains a. Producers — occupies the 1* trophic level; composed of plants and photosynthetic algae b. Consumer - herbivore — occupies the 2" trophic level; 1° consumer - carnivore — occupies the 3” trophic level; 2° consumer - omnivore — occupies either the 2" or 3" trophic levels. c. Decomposer —the last component of a food chain Energy Transfer - energy is transferred from one trophic level to another following the 10 % rule. Food Web - it is a feeding relationship that is illustrative of a series of interlinking food chains. Ecological Laws Two ecological laws can demonstrate this relationship between organisms and their environment. These include Liebig’s Law of Minimum and Shellford’s Law of Tolerance. Liebig’s Law of Minimum states that “growth and survival of an organism is dependent primarily on the nutrients that are least available. “A plant will grow and develop well where a particular nutrient critical for growth and survival is found to be inadequate or not available at all in that particular area. Take note that magnesium is an important component for the production of chlorophyll, being the central atom of pigment. Shellford’s Law of Tolerance states that “the existence of the organism is within the definable range of conditions.” This means that “ organisms then can live within a range between too much and too little”. Thus an organism han an optimum range of conditions (peak) curve and an intolerance zone, where number of organisms is at its lowest or zero. Chemistry Chemistry- is a science that studies matter, its properties, structure and the changes it undergoes together with the energy involved. Branches of Chemistry VVVV WV Analytical Chemistry Physical Chemistry Inorganic Chemistry Organic Chemistry Biochemistry Scientific method- a systematic approach/procedure in investigating nature; a combination of observations, experimentation and formulation of laws, hypotheses and theories; an organized approach to research 16 STEPS IN A SCIENTIFIC METHOD 1. Observation or Data Gathering Observations-things perceived by the senses; can be quantitative or qualitative ™@ Qualitative — consist of general observations about the system ™ Quantitative — consist of numbers obtained by various measurements of the system Examples: > Ice floats in water > Vinegar is sour > Body temperature is 39.0°C > An object weighs 1.5 kg Observation vs. Inference Inference — interpretation of the observation e.g. The clouds are dark. (observation) It might rain. (inference) 2. Are the observations answerable by any natural law? Law (natural law) - a pattern or consistency in observation of natural phenomena; a verbal or mathematical statement which relates a series of observation e.g. Law of Conservation of Mass Law of Thermodynamics 3. Defining a problem 4. Formulate a possible solution (Hypothesis Making) Hypothesis- an educated guess to explain an observation; a tentative explanation of a natural law based on observation 5. Experimentation - Is the hypothesis really the answer to the problem? 17 a. Elements- pure substance composed only of 1 type of atom; cannot be decomposed by ordinary means into simpler substances (Ex. H, He, Au, W) b. Compounds- two or more elements chemically combined in a definite and constant proportion (Ex. KCI, CH;COOH, MgCl) lonic Compounds ™ = Structural units are the cations and anions ™ Inthe solid state, the ions do not move from their positions in the lattice but only vibrate in place Properties of lonic Compounds Melting Point: High Electrical Conductivity: Solid Non-conducting Molten Conducting Aqueous Conducting Hardness: Very Hard Malleability: Brittle Covalent Molecular Substances @ Uncharged or neutral structural units (molecules) in the crystal lattice. ™@ The atoms in each molecule are held together by strong COVALENT BONDS. Properties of Covalent Molecular Compounds Melting Point: Low Electrical Conductivity: Solid Non-conducting Molten Non-conducting Aqueous Non-conducting Hardness: Soft Malleability: Brittle Covalent Network Substances @ The structural units that occupy the lattice points in the solid are ATOMS. ™ The atoms are bound to each other by strong COVALENT BONDS. Properties of Covalent Network Substances Melting Point: Very high Electrical Conductivity: Solid Non-conducting (except graphite) Molten Non-conducting Aqueous Insoluble Hardness: Very Hard Malleability: Brittle Mixture- combination of different substances in variable proportions; can be separated into its components by physical methods of separation Types of Mixtures: a. Homogeneous- uniform composition and properties throughout a given sample, but composition and properties may vary from one sample to another (e. g. solutions) b. Heterogeneous- with non-uniform properties throughout a sample where components retain their identity and phase boundaries exist (e.g. colloids, suspensions) Other Classification of Matter a. Physical States of Matter (Phases of Matter) SOLID — rigid, has definite volume and shape @ LIQUID — fluid ( has ability to flow), takes the shape of the portion of the container they occupy ™@ GAS - fluid, expands to fill up its container 20 b. Special forms based on arrangement of particles and the degree of cohesiveness Crystalline solids; amorphous solids; liquid crystals ™ Crystalline solids — high degree of cohesiveness and very orderly arrangement of particles @ Amorphous/non-crystalline solids — disordered arrangement of particles but with a high degree of cohesiveness ™ Liquid crystals — medium degree of cohesiveness and very orderly arrangement of particles; allows a degree of ordered motion of particles PROPERTIES OF MATTER Properties of Matter ro Extensiv Intensive e/Extrinsi / Intrinsic Cc Physical Extensive Properties properties that depend on the amount of material observed e.g. mass, volume, texture Intensive Properties e.g. density, odor, taste Extrinsic Properties e.g mass, volume, size Intrinsic Properties Physical properties composition of the material Chemical Properties Chemical properties that does not depend on the amount of material observed properties that can vary with different samples of the same material properties which are inherent to the substance and do not change for different samples of the same substance e.g. density, boiling and melting points, odor, taste characteristics observed or measured without changing the identity or characteristics observed or measured only by changing the identity or composition of the material; ability or inability of matter to undergo a change in its identity or composition at given conditions Changes in Matter —<=dJ_.€.4__f_, Changes in Matter Physical Change Chemical (___Change— Phase Change Synthes Decompositio Single Solid Liquid Gas T Physical Change Phase Change — determined by existing conditions of temperature and pressure Displaceme ne Double Displacemen T changes in the phase or state of a substance but not its composition e.g. changes in state (liquid > gas), shape or size (granules > powder) 21 Sublimation | Solid to Gas Deposition Gas to Solid Melting Solid to Liquid Freezing Liquid to Solid Evaporation | Liquid to Gas Condensation Gas to Liquid Chemical Change substances are converted into other substances e.g. rusting of iron, burning of wood Types of Chemical Reactions 1. SYNTHESIS / COMBINATION — formation of a bigger compound from simpler ones A+B+C...9D 2. DECOMPOSITION - A single compound is broken down to 2 or more simpler substances - Solids require heat (A) ADB+C+D+t... 3. Single Displacement- Cation or anion is replaced by an uncombined element AB+CDAC+ B 4. Double Displacement — Metathesis Exchange of partners AB +CD> AD + CB Other types: * Combustion - Reaction with O2 to form CO2, H20, N2 and oxides of any other elements present “Precipitation - Formation of a precipitate when a solution is added to another Precipitate — an insoluble or slightly soluble solid that forms when 2 solutions are mixed. Solubility Rules 1. Allnitrates are soluble. All acetates are soluble. 3. All NH," salts are soluble. 4. All salts of Group 1 are soluble. 5. All chlorides are soluble except chlorides of Hg2*, Pb and Ag* 6. All bromides are soluble except bromides of Hg2”, Pb”* and Ag* 7. Alliodides are soluble except iodides of Hg”*, Hg2*, Pb?* and Ag* 8. Most sulfates are soluble except Group 2, Pb?* and Hg. 9. All phosphates are insoluble except NH,” and Group 1. 10. All chromates are insoluble except NH," and Group 1. v Neutralization - Reaction between an acid and a base forming water and salt LAWS OF CHEMICAL COMBINATION 1. Law of Conservation of Mass ™@ Antoine Lavoisier (1743-1794) - “Father of Chemistry” 4 Established chemistry as a quantitative science + Studied combustion “In a chemical reaction, the total mass of the starting materials (reactants) is equal to the total mass of the materials produced (products).” 2. Law of Definite Proportion or Composition ™@ Joseph Proust (1754-1826) “& Showed that copper carbonate always has the ff. proportion by mass: 4 5.3 parts Cu : 4 parts O:1 partC “Any sample of a pure chemical substance contains the same elements in the same definite proportion by mass of its elements.” 3. Law of Multiple Proportion @ John Dalton (1766-1844) 22 Eugene Goldstein (1850-1930) >» Goldstein, in 1886 identified the positively charged particle and named it proton >» He used cathode with holes and observed rays passing through the holes opposite in direction to those of the cathode rays. >» The mass of this particle almost the same as the mass of the H atom > The charge is equal in magnitude (but opposite in sign to that of the electron) Bohr’s Solar System Model of the Atom asd @ Neils Bohr (1885-1962) n=3 @ In 1913, tried to explain the line spectra of hydrogen n=? Features: nel @ The electrons move about the nucleus in certain circular orbits. 6 @ = Only certain orbits and energies are allowed. @ The electron can remain in an orbit indefinitely. @ In the presence of radiant energy, the electron may absorb E and move to an orbit with higher E Quantum or Wave-Mechanical Model @ Louis de Broglie (1892-1987), Erwin Schrodinger (1887-1961), Wemer Heisenberg (1879-1976) Line Spectrum Features: Wavelength @ The energy of the electron is quantized. @ The electron moves in 3-D space around the nucleus but not in an orbit of definite radius. @ The position of the electron cannot be defined exactly, only the probability. Heisenberg Uncertainty Principle + There is a fundamental limitation to just how precisely we can know both the position and the momentum of a particle at a given time. The Nature of Light - Radiant energy that exhibits wavelike behavior and travels through space at the speed of light in a vacuum. It has oscillating magnetic and electric fields in planes perpendicular to each other. Primary Characteristics of Wave 1. WAVELENGTH, A - distance between two consecutive peaks or troughs in a wave 2. FREQUENCY, v - number of waves or cycles per second that pass a given point in space Relationship of A and v AaiN or W=C Where c= speed of light (2.9979 x 108 m/s) Atomic Spectra - The spectra produced by certain gaseous substances consist of only a limited number of colored lines with dark spaces between them. - This discontinuous spectra. - Each element has its own distinctive line spectrum- a kind of atomic fingerprint. Robert Bunsen (1811-1899) and Gustav Kirchhoff (1824-1887) + Developed the first spectroscope and used it to identify elements. 25 Max Planck (1858-1947) + Explained certain aspects of blackbody radiation + Blackbody — any object that is a perfect emitter and a perfect absorber of radiation + Sun and earth’s surface behave approximately as blackbodies + Proposed that energy, like matter, is discontinuous. * When the energy increases from one allowed value to the next, it increases by a tiny jump or quantum. + Matter could absorb or emit energy only in the whole number multiples of the quantity. E=hv where E is energy his Planck’s constant = 6.626 x 10-34 Js vis frequency So, AE =nhv Where n is an integer (1,2,3...) e Energy is “quantized” and can only occur in discrete units of size hv (packets of energy called Quantum) e Transfer of energy can only occur in whole quanta, thus, energy seems to have particulate properties. Albert Einsetein (1879-1955) + Proposed that electromagnetic radiation is itself quantized + Electromagnetic radiation can be viewed as a stream of particles called PHOTONS Summary of the Works of Einstein and Plancks + Energy is quantized. It can occur only in discrete units called quanta. + Electromagnetic radiation, which was previously thought to exhibit only wave properties, also exhibit particulate properties, thus the dual nature of light. If light has particulate properties, not just wave, does matter also have wave properties, not just particulate? Louis de Broglie (1892-1987) + Small particles of matter may at times display wavelike properties. + Fora particle with velocity, v m=h/Av Then A=h/ mv Thus, we can calculate the wavelength for a particle. + All matter exhibits both particulate and wave properties. * Large pieces of matter predominantly exhibit particulate properties because their A is so small that it is not observable. + Very small pieces of matter such as photons exhibit predominantly wave properties. + Those with intermediate mass, such as electrons, show clearly both particulate and wave properties. MODERN VIEW OF THE ATOM ALLOTROPE - elements with different forms (composed of one type of element) ISOTOPES — elements with different mass number due to the difference in the number of neutrons ISOBARS -— different elements with the same mass number but different atomic number Atom and the subatomic particles The diameter of an atom is in the order of 10° cm The nucleus is roughly 10°? cm in diameter (1/100,000 diameter of the atom) The charge of the nucleus is a unique character of the atoms of an element The charge is positive 26 Particles within the nucleus PROTON . Eugene Goldstein (1886) . from Greek “protos” meaning “first” 7 mass of p* = 1.67 x 107g 7 charge = +1.60 x 10% c . The no. of p* is a unique property of an element # of p* = atomic #, Z = nuclear charge = # of e's in a neutral atom NEUTRON m@ James Chadwick (1932) ™ Protons cannot account for the total mass of the atom ™ Has the same mass as the proton but has no charge m= Symbol: n° mass of p* + mass of n° = mass of atom (atomic mass) # of p* +# of n° =mass#,A A=Z+#ofn® ELECTRON m™ Ernest Rutherford ™@ negatively charged @ in a neutral atom : = #ofe =#ofp’=Z Summary: Particle Discovery Mass in grams_| Charge Electron discovered by JJ Thomson; name given by George | 9.11x 10% -1 Stoney Proton discovered by Rutherford in 1911, name given by | 1.67 x 10% +1 Goldstein Neutron discovered and named by James Chadwick, 1932 1.67 x 1074 0 Symbol of the Atom Atomic number, Z, is the number of protons in the 7 nucleus PaER CES ti Ex. The element N has 7 protons, so Z= 7. of the element a Mass number, A, is the sum of the number of protons UCRUIUEC SE and neutrons in the nucleus of an atom FACOG ia 4&xX. An atom with 5 protons and 5 neutrons has an atomic number of 5 and a mass number of 10 ISOTOPES @ Francis William Astron (1877-1945) - observed using the mass spectrometer that neon has 3 isotopes ™ The listed atomic mass of an element is the weighted average of the atomic masses of the naturally occurring isotopes. Atomic mass = & (% abundance)(isotopic mass) For lons ™@ (+) charge — cation - Lost electrons equal to the charge ™@ (-) charge — anion - Gained electrons equal to the charge 27 e.g. the three p-orbitals have the same energy 4. Electron Spin Quantum Number (ms) @ Values: +1/2, -1/2 ™@ The value does not depend on any of the three quantum numbers Pauli Exclusion Principle (Wolfgang Pauli 1900 1958) - Inagiven atom, no 2 e-’s can have the same set of 4 q.nos. Thus, an orbital can hold only 2 e-’s, and they must have opposite spins. Electronic Configuration — describes the manner in which electrons are arranged in an atom Ground state electronic configuration- lowest energy arrangement of electrons Excited state- allowed arrangements of electrons other than the ground state lsoelectronic- same number of electrons Rules to remember when witing ground state electronic configurations x =©Aufbau Principle- the orbitals of an atom are filled in order of increasing energy - According to the (n+l) rule. The lower the value of (n+l), the lower the energy of the orbital. If the (n+l) values of two orbitals are the same, the one with lower n is filled first. x Hund’s Rule of Multiplicity- the lowest energy arrangement of electrons in a set of degenerate orbitals is where there is a maximum number of electrons of the same spin. Electrons occupy degenerate orbitals singly before pairing. THE PERIODIC TABLE ae Periodic Table The Elements 2 of the Elements e there are 112 elements to date, 90 of which are naturally occurring Early Classifications 1. Johann Wolfgang Dobereiner’s Law of Triads (1817) - In a triad , the combining weight of the central member is the average of its partners. 2. John Newlands’ Law of Octaves (1865) - When elements are arranged in increasing atomic mass, every eighth element had similar properties. Shortcomings: ™ Some positions were forced just to maintain his proposition ™@ Some positions contained 2 elements ™@ There were no room for other elements which may be discovered 3. Julius Lothar Meyer’s Atomic Volume Curve and Periodic Table (1869) ™@ A periodic trend in properties is observed when elements are arranged in increasing atomic weights. 4. Dmitri Mendeleevs Periodic Table and Periodic Law (1869) ™ Properties of elements are periodic functions of their atomic weights 30 ™ Predicted the discovery of 10 elements The Modern Periodic Law - The properties of the elements are functions of their atomic numbers Groups @ Vertical rows ™ Previous notation: IA — VIIA, IB — VIII m@ New IUPAC* notation: 1-18 “IUPAC — International Union of Pure and Applied Chemistry ™@ Elements belonging to the same group have similar (not identical) properties Special names of some groups ™@ Group 1 — Alkali metals @ Group 2 —Alkaline earth metals ™@ Group 17 —Halogens ™ Group 18 — Noble Gases Periods @ Horizontal rows ™ Properties of elements that belong to a period show a pattern or trend that is repeated in the next period m@ Numbered 1-7 Pattern in lon Formation ™ Most elements form ions (except noble gases) ™@ Group 1 :+1 Group 15 :-3 @ Group 2: +2 Group 16 :-2 @ Group 13 : +3 Group 17 :-1 ™@ Group 14 : do not readily form ions Of the known elements, 11are gases at room temperature. four are liquids at 25°C, Hg, Br, Ga and Cs. If Fr can be prepared in large quantities, it is expected to be a liquid. Property Across a period (left to right) Down a group (top to bottom) atomic size/radius Decreasing Increasing ionization energy Increasing Decreasing affinity for electrons Increasing (upto Group 17) Decreasing Tendency to form | Decreasing Increasing Cation Tendency to form | Increasing (upto Group 17) Decreasing Anion Metallic Character Decreasing Increasing Electronegativity Increasing Decreasing Note: The size of the cation is smaller as compared to its neutral atom The size of the anion is larger as compared to its neutral atom. Atomic Size » Covalent radius — % the distance between the nuclei of two identical atoms joined by a single covalent bond. » Metallic radius — % the distance between the nuclei of 2 atoms in contact in the crystalline solid metal. lonization Energy >» Energy required to remove an e- from a gaseous atom or ion Xi > Xt & Where the atom or ion is assumed to be in its ground state Affinity for electrons 31 > Tendency of an atom or ion to attract additional e- Xq te 2X oy Electronegativity > The attraction of an atom for shared electrons. Note: Metals react with oxygen gas forming a basic oxide in water. Nonmetals react with oxygen gas forming an acidic oxide in water. CHEMICAL LANGUAGE AND SHORTHAND Chemical symbols An element is represented by a symbol which may be one or two letters; the first is capitalized and the second is in the lower case. The symbols may be derived from the Greek, German or Latin names of the elements. Binary Covalent Compounds Binary covalent compounds are formed between two non-metals A. Naming binary covalent compounds 1. Identify the elements present in the compound given by the chemical formula. The name of the more metallic element is written first. 2. Change the suffix of the less metallic element to —ide. 3. Use the prefix corresponding to the number of atoms present in the compound. Number Greek Prefix Number Greek Prefix 1 Mono- 6 Hexa- 2 Di- 7 Hepta- 3 Tri- 8 Octa- 4 Tetra- 9 Nona- 5 Penta 10 Deca- The mono- prefix is frequently omitted, particularly for well-known substances. If no prefix is use, it usually implies that no number of atoms of element is one. However, experts in nomenclature caution that this can be dangerous and suggest that it is better to include the mono- prefix. Some compounds are known only by their common names. The most common of this are: Forrmula H20 NH; PH3 Name Water Ammonia Phosphate . Writing formulas of binary compounds 1. Represent each kind of element in a compound with the correct symbol of element. 2. Indicate by a subscript the number of atoms of each element in a molecule of the compound. 3. Write the symbol of the more metallic element first. (H is an exception to this rule.) IONIC COMPOUNDS Compounds formed between metals and nonmetals are called ionic compounds. A. Naming lonic Compound 1. Write the name of the cation first, followed by the name of the anion. 2. Unlike binary covalent compounds, PREFIXES ARE NOT USE to indicate the number of ions present in the formula. 32 404g + 32009 > 36.04 g 36.04 greactants > 36.04 g products ™@ FOLLOWS THE LAW OF CONSERVATION OF MASS Balancing Chemical Equations Some important points: + Use correct chemical formulas + Adjust only the coefficients, NOT the subscripts * Balance elemental forms ( e.g. Ar, Cu, Na, O2, No, lz, Ss...) and H and O last. + Use the simplest possible set of whole no. coefficients Stoichiometry- The quantitative study of reactants and products in a chemical reaction Mole Method - The stoichiometric coefficients in a chemical equation can be interpreted as the number of moles of each substance. Steps: + Write correct chemical formulas and balance the equation. Convert the quantities into moles. Use the mole ratios to calculate moles of the required substance. Convert calculated moles to whatever units required. Three types of calculation: he Mole In 1971, at the 14" meeting of the General Conference of Weights and Measures, scientists agreed to adopt the mole as the unit of an amount of substance The mole (abbreviated mol) is the amount of substance that contains the same number of elementary particles as the number of atoms in exactly 12 grams of C-12. Ways of expressing the mole: 1. by number of particles (use Avogrado’s number, 6.02 x 10” particles per mole) 2. by mass (use molar mass) 3. by volume (use molar volume, 22.4 L at STP) Interconversions +MM x 6.02 x 10? Mass¢——_ Mole <———*"_ No. of particles x MM + 6.02 x 10% 35 The molar mass is the mass in grams of 1 mole of a substance. The molar mass is numerically equal to the atomic mass (or atomic weight) of an atom or the formula mass of a molecule, a compound or a polyatomic ion. Formula and Composition The percentage composition of a compound is a list of the percentages by weight of the elements in the compound. The percentage by weight of an element in a compound is numerically equal to the number of grams of the element that are present in 100 g of the compound Ex. What is the percentage composition of quick lime, CaO? Ans. 71.5% Ca, 28.5% O Empirical Formula- is the formula with lowest possible whole number subscripts to represent the composition of the compound. It can be determined from the % composition data. Ex. Barium carbonate, a white powder used in paints, enamels and ceramic, has the following composition: Ba, 69.58%; C, 6.090% and O, 24.03%. Determine its empirical formula Ans. BaCO; Molecular Formula- gives the actual composition or the actual number of atoms of each element present in one molecule or one formula unit of the compound Ex. Molecular formula of glucose: CeH:206 Empirical Formula of glucose: CH2O Stoichiometry of Reactions Chemical Stoichiometry- is the quantitative relationship of the amounts of reactants used and amounts of products formed in a reaction. This mass relationship is expressed in the balanced equation for the reaction. Percent yield- portion of the theoretical yield of product that is actually obtained in the reaction %yield= (actual amt of product obtained/ theoretical amt) x 100 Theoretical Yield - the amount of product that would result if all the LR reacted. - Maximum obtainable yield Actual Yield - The amount of product actually obtained from a reaction - Always less than theoretical yield Limiting reactant- reactant that is completely consumed in the reaction. It also determines the amount of products that can be formed. Excess reactant- reactant that is not completely used up in a chemical reaction TIES THAT CHEMISTRY BIND Chemical Bonds- net forces of attractions that hold atoms together Properties: ™ Bond energy — amount of energy that must be supplied to separate the atoms that make a bond ™@ Bond length — distance between 2 nuclei of 2 covalently bonded atoms ™ Bond order — number of bonds between atoms Types of Chemical Bonds a. covalent bond- pair of electrons that is shared by two atoms of nonmetals; represented by Lewis structure or electron dot formula 36 Types of Covalent Bonds: Single bond - two atoms held by one e- pair Double bond — two atoms held by 2 e pairs Triple bond — two atoms held by 3 e- pairs + Higher Bond order, shorter Bond length, higher Bond energy Polar covalent bond — one atom is more electronegative than the other atom; unequal sharing of electrons; the more electronegative atom is partially negative and the less electronegative atom is partially positive. Nonpolar covalent bond — equal sharing of electrons Coordinate Covalent Bond — the electrons being shared comes from a single atom b. ionic bond or electrovalent bond- It is the transefer of electrons from a metal to a nonmetal, i.e., the metal loses an electron while the nonmetal gains an electron converting them intro charged ions. - attraction between cations and anions c. metallic bond- the attraction between the cations in the lattice and the “sea of delocalized electrons” moving within the lattice Lewis Structure-one or a combination of Lewis symbols to represent a single atom (neutral or charged), a molecule or a polyatomic ion. - based on Octet Rule Octet rule- the observed tendency of atoms of the main block elements to lose, gain or share electrons in order to acquire an octet of electrons in their outermost main energy level It is more appropriately called Noble Gas Rule Electron Pairs could either be ™ Lone pairs — pairs of electrons localized on an atom ™@ Bonding pairs — those found in the space between the atoms Drawing Lewis Structures 1. Sum the valence electrons from all atoms (total # of e-’s) Total electrons = sum of the valence electrons of all atoms — charge 2. Determine the central atom and draw the skeletal structure. Cental atom is the most metallic atom or the least electronegative. 3. Use a pair of e-’s to form a bond between each pair of bound atoms. 4. Distribute remaining electrons to the terminal atoms to satisfy octet. 5. If there are still available electrons, put them on the central atom to satisfy octet. 6. If the central atom does not satisfy octet, move electron pair (lone pair) from the terminal atoms towards the central atom to form multiple bonds. STRICT FOLLOWERS of OCTET: C, N, O, F and H (2 electrons) 7. Check the Lewis structure. H and F are always terminal atoms and joined by a single bond. HYPERVALENT ATOM — atom that could accommodate more than the octet due to low-lying d- orbitals. RESONANCE - The use of two or more Lewis Structures to represent a particular molecule or ion. - Can be written for molecules/ions having a double or a triple bond and single bond(s). Resonance Structures- one of two or more Lewis structures for a single molecule that cannot be represented accurately by only one Lewis structure. - The true structure is the average or the “hybrid” of the resonance structures. FORMAL CHARGE- Used to evaluate non-equivalent Lewis structures (different from resonance structures) = no. of valence electron in the free state — no. of nonbonding electrons — no. of bonds 37 Stronger IMFA, higher viscosity 3. Vapor Pressure- Vapor exerted by a vapor at equilibrium with its liquid at a given temp. Stronger IMFA, lower vapor pressure 4. Enthalpy of Vaporization, AHvap- Energy that must be supplied to evaporate a liquid at 1 atm Stronger IMFA, higher AHvap 5. Boiling Point- temperature at which the vapor pressure of a liquid equals atmospheric pressure Stronger IMFA, higher boiling point 6. Freezing Point/ Melting Point- temperature at which the rate of liquid converting to solid equals the rate of solid converting to the liquid Stronger IMFA, higher FP/MP. 7. Heat of Fusion, AHfus- amount of heat required to melt a specified amount of solid at its MP Stronger IMFA, higher AHfus PHASE CHANGES AND PHASE DIAGRAMS The Kinetic Molecular Theory (KMT) Applied to gases: Gases consist of large number of particles (molecules or atoms). The gas particles are far apart. The volume therefore is negligible. The particles are in constant, random and rapid motion. They move in all directions At higher temp. the particles move faster. As the temp. of the gas increases, the ave. KE of the particles also increases. The particles are so far apart that the repulsion or attraction between them is negligible. PON> HH a KMT extended to liquids 1. Liquids consist of large number of particles. 2. These particles are close together. 3. The particles are in constant motion. Their motion is more limited compared to that in gases because of their nearness to each other but their can slip around one another. 4. The dependence between temperature and KE is the same as that in gases. 5. The particles experience attractive forces between them since they are closer to each other. KMT extended to liquids Solids like liquids and gases consist of large number of particles. 2. The particles are close together, as in liquids. The difference is that the molecules in a solid have a very well-ordered arrangement. 3. The movement of particles consist mostly of vibration within a fixed point. 4. The dependence between temp. and KE is the same as that of gases and liquids. 5. The particles experience attractive forces between them. These forces are stronger compared to that in liquids. Factors Affecting Vaporization 1. Atmospheric pressure — the lower the pressure above the liquid, the faster the rate of vaporization 2. Humidity — high humidity, slow rate of vaporization 3. Surface area —a large surface area provides more molecules the opportunity to escape 4. Motion of the atmosphere — vaporization occurs rapidly in moving air than in still air Heating Curve 40 Temperature (°C) PHASE DIAGRAM Pressure Temperature At constant temperature, phase change occurs and at _ this temperature, kinetic energy is constant while potential energy is increasing At increasing temperature, kinetic energy is increasing while potential energy is constant. @ Triple point - all 3 states are present @ Critical point: ™ Critical temp. — temp.above which the vapor cannot be liquefied no matter what pressure is applied @ Critical pressure - pressure required to produce liquefaction at the critical temp. Supercritical Fluid (SCF) ™@ Has the high density of a liquid but the low viscosity of a gas ™ Molecules in SCF, being in much closer proximity than in ordinary gases, can exert strong attractive forces on the molecules of a liquid or solid solute GASES Properties: @ Expansion Indefinite shape Compressibility Ease of mixing Low density Jan Baptista van Helmont- coined the term “chaos” or “gas” Evangelista Toricelli- showed that the air in the atmosphere exerts pressure; designed the first barometer Properties of Gases (Measurable) 1. Pressure (P)- force per unit area P= FIA Sl unit: 1 Pa= 1 N/m? Standard atmosphere : 1 atm=760 mmHg=760 torr=101325 Pa = 1.01325 bar Al 2. Volume (V)- space occupied by the gas (unit: L, mL) 1 dm?= 1b; 1cem*=1 mL 3. Temperature (T)- expressed in K, °C or °F K= °C + 273.15 Absolute zero temp= 0 K= -273.15°C > molecules stop moving Standard Temperature and Pressure (STP): 0°C, 1 atm Standard Ambient Temperature and Pressure (SATP): 25°C, | bar 4. no. of moles of gas (n) Gas Laws 1. Boyle’s Law- Robert Boyle - the volume occupied by a given mass of gas at const temp is inversely proportional to the pressure (V a 4/P) ¢ does not apply to liquids and solids ¢ applies only at moderate or low P and moderate or high T PwVi= PV 2. Charle’s Law- Jacques Charles (1746-1823) - the volume occupied by a given mass of gas at const pressure is directly proportional to temp (V aT) @ Charles is the first person to fill a balloon with hydrogen gas (Made the first solo balloon flight) Via = V2 Ti Te 3. Avogadro’s Law- Amadeo Avogadro (1776-1856) - for a gas at const T and P, V is directly related to the no. of moles of gas (V an) Molar volume- one mole of any gas at STP occupies a volume of 22.4 L Via = Ve ny m2 4. Gay-Lussac’s law- the pressure occupied by a given mass of gas at const volume is directly proportional to temp (P a T) Pi= Be Ti Ta 5. Combined gas law (PV)IT =k, hence (P1V1)/T1 = (P2V2/T2 6. Ideal Gas Law PV= nRT Where P = Pressure (atm) V = Volume (L) n =no. of moles (mol) R = Universal gas constant= 0.0821 L-atm/mol-K T = Temperature (K) Daltons’s Law of Partial Pressures ™ For a mixture of gases in a container, the total pressure exerted is the sum of the pressures that each gas would exert if it were alone. Praat = Pi + P2 + Ps +... + Pr @ Where P,, P2 and P; are partial pressures of the gas each gas would exert if it were alone in the container. 42 pH = -log [H30*] pOH = -log [OH] pH + pOH = 14 Strong Acids @ HCl HBr @ Hi HClO, m@ HNO; H2SO, (1st ionization only) Strong Bases ™@ Hydroxides of Groups 1 and 2 Weak Acids and Bases —ionizes to small extent The larger the Ka (ionization constant of acid), the stronger the acid, greater [H30*] The larger the Kb (ionization constant of base), the stronger the base, greater [OH] Lewis Definition (Gilbert Newton Lewis, 1875-1946) ™ Base -a substance that can donate an e pair ™ Acid —a substance that can accept an e- pair Titration - aneutralization reaction - a solution is gradually added to another solution until the solute of the first solution has completely reacted with the solute of the second solution Indicator — an organic compound that changes color depending on the pH e.g. phenolphthalein colorless — acidic faint pink — neutral pink — basic Equivalence Point- the point at which the solute of the first solution has completely reacted with the solute of the other solution Endpoint — approximates the equivalence point. It is very close to the equivalence point. Standardization — it is the process of determining the concentration of a solution using a standard solution. The solution has a known concentration. Titrant- the solution usually placed on the buret. This is usually the solution of known concentration. Analyte- the solution of unknown concentration usually placed in the Erlenmeyer flask. BUFFERS - Asolution that resists drastic changes in pH when small amounts of acids or bases are added. Components: > Aweak acid and its conjugate base (in salt form) OR > Aweak base and its conjugate acid (in salt form) pKa =-log Ka pKb =- log Kb Henderson-Hasselbach equation: pH = pKa + log [baseJ/[acid] CHEMICAL EQUILIBRIUM - The state in which the forward and backward reactions continue to occur but the concentrations of all reactants and products remain constant with time. Characteristics: 1. Dynamic Situation — the forward and backward reactions continue to exist 2. Balance - the rate of forward reaction is equal to the rate of backward reaction AS SCIENCE REVIEWER Definitions of Science General Science % An organized body of knowledge gathered over a long period of time to explain the world we live in. % Knowledge or a system covering general truths or the operation of general laws especially as obtained and tested through scientific method. Scientific Method Gathering Preliminary data Formulating a hypothesis* Testing of the hypothesis Analysis and Interpretation of data Drawing of Conclusion OARWON> Identifying the problem (Questioning) Independent Variable — variable changed by the experimenter Dependent Variable — variable that responds to the variable that is changed in the experiment. Experimental group — groups that receive treatment. Control group — opposite of Experimental. % hypothesis — it is what we think the answer to the question is and it should stated in terms of the variables defined. Laws and Theories *Scientific law — a description of a natural occurrence that has been observed many times. “Scientific theory — a reasonable explanation of a scientific law. It is derived from a hypothesis that has been supported by repeated testing. “Model — helps visualize occurrences and objects that cannot be observed directly. Note: Scientific lavs and theories cannot be proven absolutely. They are maintained as all observations support them. Measurements % In science, the metric system is used in all measurements for its convenience and simplicity. % The International System of Units (SI) uses the seven base quantities and units given below: Physical Quantity Unit Name (symbol) Mass Kilogram, kg Length Meter, m Time Second, s Amount of Substance Mole, mol Temperature Kelvin, K Electric current Ampere, A Luminous intensity Candela, cd A. Reading Metric Measurements No. of significant digits = no. of certain digits + one certain digit (0 or 5) Example 1: The diagram below is a metric ruler used to measure the length of a pencil. How long is the pencil? } a | | | 8 cm 9 10 The smallest fra centimet 2 metric ruler is 0.1 cm. This corresponds to the last certain digit in any measurement. The pointer reads 9.0 cm. One uncertain digit should be added. In this case it is 0. Answer: Length of pencil = 9.00 cm B. Converting Metric Units Conversion of metric units is easily performed, Mega ‘108 Decimal point Kilo 10 moves to the left Deka 10? Hector 10° Base unit 10° Deci 107 Centi 10% ‘sve tothe Milli 10° right Micro 10° Example 2: How many grams are there in 37.d centigrams? %& To convert 37.5 cg to grams, count the number of steps from centi to base unit. Since it moves upward, the movement of the decimal point is to the left. Answer: 0.375 g Major Regions of the Earth Lithosphere — the solid part and the largest portion of the earth Hydrosphere — the liquid part. It covers about 71% of the earth’s surface Atmosphere — the gaseous portion that envelops the earth Biosphere — the region where living things are found. RONS Rocks and Minerals Everywhere you look, you find rocks of different shapes and sizes. What is important to remember about rocks is the way they were formed. The varying conditions for the rock formation influence the characteristics that each rock develops, %& Igneous rocks — formed from hardened magma and lava. e.g. Rhyolite, Granite, Basalt, etc. % Sedimentary rocks — form from deposited fragments or particles of other rocks that have been weathered and eroded. e.g. limestone, conglomerate, dolomite, shale EXCERCISES FOR GENERAL SCIENCE Match each definition in column B with the correct word in column C. Write the letter of the correct word and the first letter of the correct word in the space provided in column A. A B c 1. A-systematic process of gaining information a. Law 2. Avariable that is changed by the experimenter b. Theory 3. It responds to the variable that is changed in the | c. Scientific experiment method 4. A process that results to the breaking of rocks into smaller | d. Independent pieces variable 5. Process by which infrared radiation from the earth’s surface | e. Dependent is absorbed by water vapor and carbon dioxide in the | variable atmosphere It is a description of a repeatable natural occurrence A reasonable explanation of natural occurrences A sample group that receives a treatment Helps visualize occurrences and objects that cannot be observed directly . An educated guess. . A change in constitution of a rock brought about by pressure and heat within the earth’s crust . Solid earth materials that have a definite chemical composition and molecular structure . A logical conclusion that can be drawn from an observation . This is done to gather important information before designing an experiment. . A periodic rise and fall of ocean water caused by the moon and the sun. . The layer of the atmosphere where we live . Seasonal wind that blows between continent and an ocean . Produced by the cooling and crystallization of molten lava or magma . Process of transporting rock particles f. Weathering g. Igneous rock h. Research i. Troposphere j. Minerals k.monsoon 1. Model m. M etamorphism n. Tide o. Greenhouse effect p. Hypothesis q. Experimental group r. Inference s. Control group t. Conclusion u. Erosion v. Sedimentation w. M etamorphic rocks x. rocks I|.Computation 1. An adult inhales 10 000 L of air a day. What is the equivalent volume in cubic millimeters? 2. One stick of cigarette of a particular brand contains 40 mg tar. If a person smokes 20 cigarette sticks in a day, how many grams of tar does he consume in a week? 3. The nearest star to the sun is 2.52 x 10°? miles away. How far is this in kilometer? IlLEssay 1. What is the difference between revolution and rotation? 2. Unlike earth, which is surrounded by sea of gas, Mercury has no atmosphere. State a possible explanation for the lack of atmosphere in this planet. Biology Biology — the branch of science that deals with the study of living systems and life processes. A. Cells This is probably the most basic term that you would need to know. All living systems are composed of cells. They are the basic unit of structure and fuction in living things. Following is an illustration and concept map of a cell and the different structures contained in it. Cell wall/cell membrane Except for the Cell ———} cytoplasm Except for the! nucleus [|_— protoplasm -—nitochondrion t—chloroplast |__rivosome +—Endoplasmic reticulum t——Golgi apparatus |___lysosome |_centriole [Microtubules and microfilaments Organelles are structures with specific functions found within living cells. % Nucleus — This organelle is arguably the most important structure in the cell because it serves as the control center in which individual functions of the other organelles are coordinated. Cell wall/cell membrane — the cell wall in plant cells and in some monerans and protests provides rigidity for support to the cells and a characteristic shape for functionality and structure. The cell membrane on the other hand is selectively permeable. site where ATPs are abundantly synthesized. algae. %* Ribosome — this serves as the site of protein synthesis. Endoplasmic Reticulum — These organelles serve as channels or passageways through %* Mitochondrion — this organelle is also called as “powerhouse of the cell”. It serves as the ** Chloroplast — this serves as the site of photosynthesis among plants and photosynthetic which materials are transported to the different parts of the cell. Differences between plant and animal cells Centriole — this serves for cytokinetic purposes and is very common among dividing cells Lysosome — the structure is also called “suicidal bag” as it releases digestive juices Golgi apparatus — this serves for selection and packaging of cellular materials. Structure Plants Animals 1. cell wall Present. Absent 2. chloroplast Present Absent 3. centriole Absent Present. 4. lysosome Absent Present 5. vacuole Onellarge Many/small How did the concept of the cell come about? The Cell Theory serves as the basis on which everything that we know about the cell is anchored. There are three elements to this theory; 1. All living things are made up of cells. 2. Cells are the basic unit of structure and function in living systems. 3. All cells come from preexisting cells. Like any biological structure, the cell is composed of biomolecules that are intricately combined to enable the cell to perform its metabolic functions. a. Carbohydrates — immediate source of energy - elemental composition: C,H, O - building blocks: monosaccahrides - e.g. sucrose (table sugar), maltose, amylase b. Fats/Lipids — these molecules serve as another source of energy after carbohydrates - elemental composition: C,H, O - building blocks: fatty acids and a glycerol backbone - e.g. waxes, oils, and cholesterol c. Proteins — these molecules serve as sources of building materials. - elemental composition: C,H, O,N, S - building blocks: amino acids - e.g. amylase, actin and myosin d. Nucleic Acids — these molecules include the RNA’s and the DNA’s - elemental composition: C, H,O,N, P - building blocks: nucleotides Cells according to complexity %& Prokaryotic cells — have no membrane-bound nucleus and organelles; typical of bacteria and blue-green algae % Eukaryotic cells — have membrane-bound nucleus and organelles; typical of protests, fungi, plants, and animals. Cell Transport Passive Transport — does not require the expenditure of energy; moves particles through the concentration gradient. Active transport — requires the expenditure of energy; moves particles against the concentration gradient. Diffusion - this refers to the process in which molecules of solvent move from an area of high concentration to an area of low concentration. Osmosis — this refers to the diffusion of particles or molecules across selectively permeable membrane. Cell Reproduction This refers to the process by which cells divide to produce daughter cells. It involves either mitosis if somatic or body cells are involves or meiosis if germ or sex cells are involved. Mitosis - refers to the division of the somatic cells - also referred to as equational dvision because the ploidy number of the daughter cells is equal to the ploidy number of the dividing cell. The cells in all organisms grow and reproduce by cell division. A unicellular bacterium, after doubling in size, can reproduce by dividing into two cells. In multicellular organisms like man, increase in size is attained by dividing its constituent cells. Gene Segregation and Interaction Dominant Allele - alternative trait that is expressed in the phenotype. Recessive Allele — alternative trait whose expression is marked in the phenotype. Law of Dominance - state that only dominant alleles are expressed in the phenotype and that recessive alleles are masked among hybrids but are manifested among pure breeds. Law of Co-dominance - states that two equally dominant alleles are equally expressed in the phenotype and that no blending is achieved. Law of Incomplete Dominance -— states that among multi-allelic traits, two dominant alleles that are not dominant enough to mask the expression of one another, are incompletely expressed in the phenotype, hence a blended trait is achieved. Mendel’s law may be separated into two rules: first, the law of Independent Segregation of Alleles and second, the Law of Independent Assortment. “Law of Independent Segregation states that the alleles in a gene pair separate cleanly from each other during meiosis. “Law of Independent Assortment states that the alleles of the different genes separate cleanly from each other and randomly combining during meiosis. These laws can be illustrated using monohybrid and dihybrid cross: a. Monohybrid Cross One of the pairs of alternative characters in sweet peas studied by Mendel waqs round vs wrinkled seed. These distinctive characters or traits are called phenotype while the gene or genetic content coding for these traits is the genotype. In example below, both parents are homozygous so that the round (P1) and winkled (P2) parents have the RR and rr genotypes, respectively. The gametes produced after meiosis by P1 is R and by P2 is r so the progeny of the first filial generation (F1) have heterozygous (Rr) genotypes. Since R is dominant over r, then the F1’s have round phenotype. This is an example of complete dominance. R masks the expression of r. This is the dominant allele. The allele that is masked (r ) is the recessive. Female Parent (P1) Male Parent (P2) Phenotype: Round Wrinkled Genotype RR rr Gametes R r Fertilization F1 genotype: Rr Phenotype; Round To demonstrate that the F1’s are heterozygous, a testcross can be conducted wherein the F1 plants are crossed to the homozygous recessive parents (rr). The recessive parent contributes 10 the gametes (r ) while the other parent contributes R and r. Testcross results in 1 Rr (round): 1 rr (wrinkled) or 1:1 segregation ratio. Rr x tr Gametes r R Rr (round) r rr (wrinkled) Genotypic Ratio: 1Rr : der Phenotypic Ratio: 1round : 1 wrinkled b. Dihybrid Cross The members of gene pairs located on different homologous chromosome segregate independently of each other during meiosis. Mendel studied two phenotypes, texture and color of seeds with two alternative traits; round and yellow seeds vs. wrinkled and green seeds. He crossed pure breeding round, yellow seeded plants with pure breeding wrinkled, green seeded plants. The F1 progenies were all yellow round seeded plants. The F2’s gave 315 round, yellow: 101 wrinkled yellow; 108 round, green and 32 wrinkled, green plants. Approximately 9:3:3:1. The method used in getting the genotypic ratio among F2 progeny is called Punnett Square or Checkerboard method. Molecular Basis of Heredity The first part dealt with the physical basis of heredity — the chromosomes. Chromosomes are the carriers of the multitude of genes. Genes or hereditary units, on the other hand, are actually fragments or portions of the deoxyribonucleic acid or DNA. A chromosome is made up of one very long DNA packaged with histones to fit inside a minute nucleus of the cell. Eukaryotic cells with several chromosomes would, therefore, contain more than one molecule of DNA. Prokaryotic cells and viruses generally possess one long molecule of DNA either naked or associated with proteins but not as organized as compared to eukaryotic chromosomes. The DNA has been tagged as the genetic material of all organisms with the exception of some viruses with ribonucleic acid or RNA as their genetic material. Central Dogma of Molecular Biology DNA as the genetic material is capable of transmitting biological information from a parent cell to its daughter cells and, in a broader perspective, from one generation to another. The information stored in its base sequence is copied accurately by replication. Replication is a process of faithfully copying a DNA to produce two DNA molecules identical to the parent DNA. These DNA molecules are then passed on to the daughter cells via the chromosomes during cell division. The information stored in the DNA when expressed will result to a particular trait of an individual. The trait is expressed through the action of proteins either directly or indirectly. The central dogma of molecular biology consists of three general processes namely: replication (DNA synthesis), transcription (RNA synthesis) and translation (protein synthesis). The transfer of information from cell to cell or from generation to generation is achieved by replication. On the other hand, the transfers of information from the DNA to the proteins involve two processes: transcription and translation. Generally, all organisms follow this mode of transfer except for some viruses that undergo reverse transcription. 11 Transcription Translation DNA RNA = —W—____» PROTEIN 4--------- Reverse Transcription Mutation — changes in the genetic materials that are essentially heritable. a. Deletion — refers to a segment of base pairs in the DNA that is spliced off. b. Substitution — refers to a segment of the base pairs in the DNA that is replaced by a different series of base pairs. C. Translocation — refers to segments of base pairs that are differently positioned. d. insertion — refers to base pairs that are added to segment of DNA. Evolution — this process refers to the gradual change in populations through time. D. Animal Development (30 minutes) Animal Cells, Tissues and Tissue Organization Animal tissues are generally classified into four categories: Epithelium, Connective Tissue, Muscle and Nerve. These animal tissues make up all the organ systems of the body. o Epithelium, in its simplest form, is composed of a single continuous layer of cells of the same type covering an extemal or internal surface. o Connective Tissue, has the widest range encompassing the vascular tissue(blood and lymph), CT proper, cartilage and bone. o Muscular tissue consists of elongated cells organized in long units of structures called muscle fibers or muscle cells. The two general categories of muscle, smooth and striated. Striated or skeletal muscle functions for voluntary control while smooth muscle functions for involuntary contractions. o The nerve cells or neurons comprising the nervous tissue each possess a cell body which contains the nucleus and the surrounding cytoplasm. The process come in contact with other nerve cells, or with other effector cells through a point of contact called synapse. Animal Development Animal development is a series of events that is controlled by the genetic information in the nucleus and factors in the cytoplasm. It starts with fertilization and ends into the arrangement of cells which gives the embryo its distinct form. Features which are unique to organism such as the shape of the face, location and number of limbs and arrangement of brain parts are molded by cell movements in response to the action of genes in the nucleus and molecules in the cytoplasm. Stages of Development a. Gametogenesis 12 where organic matter is reduced to simpler substances. Structurally therefore, the ecosystem can composite the following, that is, the abiotic factors; the producers; the macroconsumer; and the decomposers. The abiotic component, on the other hand covers climatic, edaphic (soil) and topographic factors. Climate includes light, temperature, precipitation and wind. Light influences the biotic components in many ways, as in photosynthesis, flowering seed dormancy, leaf senescence, nesting, migration and hibernation. Light quality penetrating with increasing water depths also determines the type of producers (i.e. green algae in shallow water and red algae at greater depths). Temperature affects living organisms by influencing their metabolic processes. It can determine the type of vegetation in different ecosystems depending on its availability. Water as the universal solvent plays an important role in the ecosystem as it serves as a medium for biochemical processes. It can determine the type of vegetation in terrestrial ecosystems depending on its availability. In aquatic ecosystems, however, what plays important roles are salinity, ph, temperature and dissolved oxygen. The atmosphere is a major reservoir of nutrients important to life. Nutrient cycling in the atmosphere is further facilitated by wind. The latter also accelerates evapo-transcription rate causing damage to plant structures. However, it plays an important role in facilitating seed dispersal and in the distribution of plants and animals. Biome - is a geographical unit uniformly affected by a common prevailing climate havin a similar flora and fauna. Terrestrial biomes the world over include: * Tropical rainforests — which have the highest species diversity Coniferous forests — which harbors the pine-trees Deserts — characterized by very low species diversity Grasslands — also variously called savannahs, steppes and scrubs Taigas and Tundras-characterized by permafrosts Aquatic biomes on the other hand include: * Marshlands Lakes Seas and oceans and Estuaries Five Kingdoms Monera — prokaryotic; unicellular; includes the bacteria and the cyanobacteria. Protista — eukaryotic; unicellular/colonial; includes the flagellates, the ciliates, the sarcodines and the algal systems. Fungi — eukaryotic; unicellular (yeasts) and multicellular (molds and mushrooms). Plantae — eukaryotic; multicellular; Animalia — eukaryotic; multicellular; includes the invertebrates and vertebrates. Ecological Relationships a. Mutualism — “give and take” relationship b. Commensalisms- a relationship where the commensal is benefited and the host is neither benefited nor harmed Parasitism — a relationship where the parasite is benefited and the host is harmed Competition — neither organism in this relationship is benefited e. Predation —a relation where the predator is benefited and the prey is harmed 2° 15 Food Chain Three components of a Food Chains a. Producers — occupies the 1* trophic level; composed of plants and photosynthetic algae b. Consumer - herbivore — occupies the 2" trophic level; 1° consumer - carnivore — occupies the 3” trophic level; 2° consumer - omnivore — occupies either the 2" or 3" trophic levels. c. Decomposer —the last component of a food chain Energy Transfer - energy is transferred from one trophic level to another following the 10 % rule. Food Web - it is a feeding relationship that is illustrative of a series of interlinking food chains. Ecological Laws Two ecological laws can demonstrate this relationship between organisms and their environment. These include Liebig’s Law of Minimum and Shellford’s Law of Tolerance. Liebig’s Law of Minimum states that “growth and survival of an organism is dependent primarily on the nutrients that are least available. “A plant will grow and develop well where a particular nutrient critical for growth and survival is found to be inadequate or not available at all in that particular area. Take note that magnesium is an important component for the production of chlorophyll, being the central atom of pigment. Shellford’s Law of Tolerance states that “the existence of the organism is within the definable range of conditions.” This means that “ organisms then can live within a range between too much and too little”. Thus an organism han an optimum range of conditions (peak) curve and an intolerance zone, where number of organisms is at its lowest or zero. Chemistry Chemistry- is a science that studies matter, its properties, structure and the changes it undergoes together with the energy involved. Branches of Chemistry VVVV WV Analytical Chemistry Physical Chemistry Inorganic Chemistry Organic Chemistry Biochemistry Scientific method- a systematic approach/procedure in investigating nature; a combination of observations, experimentation and formulation of laws, hypotheses and theories; an organized approach to research 16 STEPS IN A SCIENTIFIC METHOD 1. Observation or Data Gathering Observations-things perceived by the senses; can be quantitative or qualitative ™@ Qualitative — consist of general observations about the system ™ Quantitative — consist of numbers obtained by various measurements of the system Examples: > Ice floats in water > Vinegar is sour > Body temperature is 39.0°C > An object weighs 1.5 kg Observation vs. Inference Inference — interpretation of the observation e.g. The clouds are dark. (observation) It might rain. (inference) 2. Are the observations answerable by any natural law? Law (natural law) - a pattern or consistency in observation of natural phenomena; a verbal or mathematical statement which relates a series of observation e.g. Law of Conservation of Mass Law of Thermodynamics 3. Defining a problem 4. Formulate a possible solution (Hypothesis Making) Hypothesis- an educated guess to explain an observation; a tentative explanation of a natural law based on observation 5. Experimentation - Is the hypothesis really the answer to the problem? 17 a. Elements- pure substance composed only of 1 type of atom; cannot be decomposed by ordinary means into simpler substances (Ex. H, He, Au, W) b. Compounds- two or more elements chemically combined in a definite and constant proportion (Ex. KCI, CH;COOH, MgCl) lonic Compounds ™ = Structural units are the cations and anions ™ Inthe solid state, the ions do not move from their positions in the lattice but only vibrate in place Properties of lonic Compounds Melting Point: High Electrical Conductivity: Solid Non-conducting Molten Conducting Aqueous Conducting Hardness: Very Hard Malleability: Brittle Covalent Molecular Substances @ Uncharged or neutral structural units (molecules) in the crystal lattice. ™@ The atoms in each molecule are held together by strong COVALENT BONDS. Properties of Covalent Molecular Compounds Melting Point: Low Electrical Conductivity: Solid Non-conducting Molten Non-conducting Aqueous Non-conducting Hardness: Soft Malleability: Brittle Covalent Network Substances @ The structural units that occupy the lattice points in the solid are ATOMS. ™ The atoms are bound to each other by strong COVALENT BONDS. Properties of Covalent Network Substances Melting Point: Very high Electrical Conductivity: Solid Non-conducting (except graphite) Molten Non-conducting Aqueous Insoluble Hardness: Very Hard Malleability: Brittle Mixture- combination of different substances in variable proportions; can be separated into its components by physical methods of separation Types of Mixtures: a. Homogeneous- uniform composition and properties throughout a given sample, but composition and properties may vary from one sample to another (e. g. solutions) b. Heterogeneous- with non-uniform properties throughout a sample where components retain their identity and phase boundaries exist (e.g. colloids, suspensions) Other Classification of Matter a. Physical States of Matter (Phases of Matter) SOLID — rigid, has definite volume and shape @ LIQUID — fluid ( has ability to flow), takes the shape of the portion of the container they occupy ™@ GAS - fluid, expands to fill up its container 20 b. Special forms based on arrangement of particles and the degree of cohesiveness Crystalline solids; amorphous solids; liquid crystals ™ Crystalline solids — high degree of cohesiveness and very orderly arrangement of particles @ Amorphous/non-crystalline solids — disordered arrangement of particles but with a high degree of cohesiveness ™ Liquid crystals — medium degree of cohesiveness and very orderly arrangement of particles; allows a degree of ordered motion of particles PROPERTIES OF MATTER Properties of Matter ro Extensiv Intensive e/Extrinsi / Intrinsic Cc Physical Extensive Properties properties that depend on the amount of material observed e.g. mass, volume, texture Intensive Properties e.g. density, odor, taste Extrinsic Properties e.g mass, volume, size Intrinsic Properties Physical properties composition of the material Chemical Properties Chemical properties that does not depend on the amount of material observed properties that can vary with different samples of the same material properties which are inherent to the substance and do not change for different samples of the same substance e.g. density, boiling and melting points, odor, taste characteristics observed or measured without changing the identity or characteristics observed or measured only by changing the identity or composition of the material; ability or inability of matter to undergo a change in its identity or composition at given conditions Changes in Matter —<=dJ_.€.4__f_, Changes in Matter Physical Change Chemical (___Change— Phase Change Synthes Decompositio Single Solid Liquid Gas T Physical Change Phase Change — determined by existing conditions of temperature and pressure Displaceme ne Double Displacemen T changes in the phase or state of a substance but not its composition e.g. changes in state (liquid > gas), shape or size (granules > powder) 21 Sublimation | Solid to Gas Deposition Gas to Solid Melting Solid to Liquid Freezing Liquid to Solid Evaporation | Liquid to Gas Condensation Gas to Liquid Chemical Change substances are converted into other substances e.g. rusting of iron, burning of wood Types of Chemical Reactions 1. SYNTHESIS / COMBINATION — formation of a bigger compound from simpler ones A+B+C...9D 2. DECOMPOSITION - A single compound is broken down to 2 or more simpler substances - Solids require heat (A) ADB+C+D+t... 3. Single Displacement- Cation or anion is replaced by an uncombined element AB+CDAC+ B 4. Double Displacement — Metathesis Exchange of partners AB +CD> AD + CB Other types: * Combustion - Reaction with O2 to form CO2, H20, N2 and oxides of any other elements present “Precipitation - Formation of a precipitate when a solution is added to another Precipitate — an insoluble or slightly soluble solid that forms when 2 solutions are mixed. Solubility Rules 1. Allnitrates are soluble. All acetates are soluble. 3. All NH," salts are soluble. 4. All salts of Group 1 are soluble. 5. All chlorides are soluble except chlorides of Hg2*, Pb and Ag* 6. All bromides are soluble except bromides of Hg2”, Pb”* and Ag* 7. Alliodides are soluble except iodides of Hg”*, Hg2*, Pb?* and Ag* 8. Most sulfates are soluble except Group 2, Pb?* and Hg. 9. All phosphates are insoluble except NH,” and Group 1. 10. All chromates are insoluble except NH," and Group 1. v Neutralization - Reaction between an acid and a base forming water and salt LAWS OF CHEMICAL COMBINATION 1. Law of Conservation of Mass ™@ Antoine Lavoisier (1743-1794) - “Father of Chemistry” 4 Established chemistry as a quantitative science + Studied combustion “In a chemical reaction, the total mass of the starting materials (reactants) is equal to the total mass of the materials produced (products).” 2. Law of Definite Proportion or Composition ™@ Joseph Proust (1754-1826) “& Showed that copper carbonate always has the ff. proportion by mass: 4 5.3 parts Cu : 4 parts O:1 partC “Any sample of a pure chemical substance contains the same elements in the same definite proportion by mass of its elements.” 3. Law of Multiple Proportion @ John Dalton (1766-1844) 22 Eugene Goldstein (1850-1930) >» Goldstein, in 1886 identified the positively charged particle and named it proton >» He used cathode with holes and observed rays passing through the holes opposite in direction to those of the cathode rays. >» The mass of this particle almost the same as the mass of the H atom > The charge is equal in magnitude (but opposite in sign to that of the electron) Bohr’s Solar System Model of the Atom asd @ Neils Bohr (1885-1962) n=3 @ In 1913, tried to explain the line spectra of hydrogen n=? Features: nel @ The electrons move about the nucleus in certain circular orbits. 6 @ = Only certain orbits and energies are allowed. @ The electron can remain in an orbit indefinitely. @ In the presence of radiant energy, the electron may absorb E and move to an orbit with higher E Quantum or Wave-Mechanical Model @ Louis de Broglie (1892-1987), Erwin Schrodinger (1887-1961), Wemer Heisenberg (1879-1976) Line Spectrum Features: Wavelength @ The energy of the electron is quantized. @ The electron moves in 3-D space around the nucleus but not in an orbit of definite radius. @ The position of the electron cannot be defined exactly, only the probability. Heisenberg Uncertainty Principle + There is a fundamental limitation to just how precisely we can know both the position and the momentum of a particle at a given time. The Nature of Light - Radiant energy that exhibits wavelike behavior and travels through space at the speed of light in a vacuum. It has oscillating magnetic and electric fields in planes perpendicular to each other. Primary Characteristics of Wave 1. WAVELENGTH, A - distance between two consecutive peaks or troughs in a wave 2. FREQUENCY, v - number of waves or cycles per second that pass a given point in space Relationship of A and v AaiN or W=C Where c= speed of light (2.9979 x 108 m/s) Atomic Spectra - The spectra produced by certain gaseous substances consist of only a limited number of colored lines with dark spaces between them. - This discontinuous spectra. - Each element has its own distinctive line spectrum- a kind of atomic fingerprint. Robert Bunsen (1811-1899) and Gustav Kirchhoff (1824-1887) + Developed the first spectroscope and used it to identify elements. 25 Max Planck (1858-1947) + Explained certain aspects of blackbody radiation + Blackbody — any object that is a perfect emitter and a perfect absorber of radiation + Sun and earth’s surface behave approximately as blackbodies + Proposed that energy, like matter, is discontinuous. * When the energy increases from one allowed value to the next, it increases by a tiny jump or quantum. + Matter could absorb or emit energy only in the whole number multiples of the quantity. E=hv where E is energy his Planck’s constant = 6.626 x 10-34 Js vis frequency So, AE =nhv Where n is an integer (1,2,3...) e Energy is “quantized” and can only occur in discrete units of size hv (packets of energy called Quantum) e Transfer of energy can only occur in whole quanta, thus, energy seems to have particulate properties. Albert Einsetein (1879-1955) + Proposed that electromagnetic radiation is itself quantized + Electromagnetic radiation can be viewed as a stream of particles called PHOTONS Summary of the Works of Einstein and Plancks + Energy is quantized. It can occur only in discrete units called quanta. + Electromagnetic radiation, which was previously thought to exhibit only wave properties, also exhibit particulate properties, thus the dual nature of light. If light has particulate properties, not just wave, does matter also have wave properties, not just particulate? Louis de Broglie (1892-1987) + Small particles of matter may at times display wavelike properties. + Fora particle with velocity, v m=h/Av Then A=h/ mv Thus, we can calculate the wavelength for a particle. + All matter exhibits both particulate and wave properties. * Large pieces of matter predominantly exhibit particulate properties because their A is so small that it is not observable. + Very small pieces of matter such as photons exhibit predominantly wave properties. + Those with intermediate mass, such as electrons, show clearly both particulate and wave properties. MODERN VIEW OF THE ATOM ALLOTROPE - elements with different forms (composed of one type of element) ISOTOPES — elements with different mass number due to the difference in the number of neutrons ISOBARS -— different elements with the same mass number but different atomic number Atom and the subatomic particles The diameter of an atom is in the order of 10° cm The nucleus is roughly 10°? cm in diameter (1/100,000 diameter of the atom) The charge of the nucleus is a unique character of the atoms of an element The charge is positive 26 Particles within the nucleus PROTON . Eugene Goldstein (1886) . from Greek “protos” meaning “first” 7 mass of p* = 1.67 x 107g 7 charge = +1.60 x 10% c . The no. of p* is a unique property of an element # of p* = atomic #, Z = nuclear charge = # of e's in a neutral atom NEUTRON m@ James Chadwick (1932) ™ Protons cannot account for the total mass of the atom ™ Has the same mass as the proton but has no charge m= Symbol: n° mass of p* + mass of n° = mass of atom (atomic mass) # of p* +# of n° =mass#,A A=Z+#ofn® ELECTRON m™ Ernest Rutherford ™@ negatively charged @ in a neutral atom : = #ofe =#ofp’=Z Summary: Particle Discovery Mass in grams_| Charge Electron discovered by JJ Thomson; name given by George | 9.11x 10% -1 Stoney Proton discovered by Rutherford in 1911, name given by | 1.67 x 10% +1 Goldstein Neutron discovered and named by James Chadwick, 1932 1.67 x 1074 0 Symbol of the Atom Atomic number, Z, is the number of protons in the 7 nucleus PaER CES ti Ex. The element N has 7 protons, so Z= 7. of the element a Mass number, A, is the sum of the number of protons UCRUIUEC SE and neutrons in the nucleus of an atom FACOG ia 4&xX. An atom with 5 protons and 5 neutrons has an atomic number of 5 and a mass number of 10 ISOTOPES @ Francis William Astron (1877-1945) - observed using the mass spectrometer that neon has 3 isotopes ™ The listed atomic mass of an element is the weighted average of the atomic masses of the naturally occurring isotopes. Atomic mass = & (% abundance)(isotopic mass) For lons ™@ (+) charge — cation - Lost electrons equal to the charge ™@ (-) charge — anion - Gained electrons equal to the charge 27 e.g. the three p-orbitals have the same energy 4. Electron Spin Quantum Number (ms) @ Values: +1/2, -1/2 ™@ The value does not depend on any of the three quantum numbers Pauli Exclusion Principle (Wolfgang Pauli 1900 1958) - Inagiven atom, no 2 e-’s can have the same set of 4 q.nos. Thus, an orbital can hold only 2 e-’s, and they must have opposite spins. Electronic Configuration — describes the manner in which electrons are arranged in an atom Ground state electronic configuration- lowest energy arrangement of electrons Excited state- allowed arrangements of electrons other than the ground state lsoelectronic- same number of electrons Rules to remember when witing ground state electronic configurations x =©Aufbau Principle- the orbitals of an atom are filled in order of increasing energy - According to the (n+l) rule. The lower the value of (n+l), the lower the energy of the orbital. If the (n+l) values of two orbitals are the same, the one with lower n is filled first. x Hund’s Rule of Multiplicity- the lowest energy arrangement of electrons in a set of degenerate orbitals is where there is a maximum number of electrons of the same spin. Electrons occupy degenerate orbitals singly before pairing. THE PERIODIC TABLE ae Periodic Table The Elements 2 of the Elements e there are 112 elements to date, 90 of which are naturally occurring Early Classifications 1. Johann Wolfgang Dobereiner’s Law of Triads (1817) - In a triad , the combining weight of the central member is the average of its partners. 2. John Newlands’ Law of Octaves (1865) - When elements are arranged in increasing atomic mass, every eighth element had similar properties. Shortcomings: ™ Some positions were forced just to maintain his proposition ™@ Some positions contained 2 elements ™@ There were no room for other elements which may be discovered 3. Julius Lothar Meyer’s Atomic Volume Curve and Periodic Table (1869) ™@ A periodic trend in properties is observed when elements are arranged in increasing atomic weights. 4. Dmitri Mendeleevs Periodic Table and Periodic Law (1869) ™ Properties of elements are periodic functions of their atomic weights 30 ™ Predicted the discovery of 10 elements The Modern Periodic Law - The properties of the elements are functions of their atomic numbers Groups @ Vertical rows ™ Previous notation: IA — VIIA, IB — VIII m@ New IUPAC* notation: 1-18 “IUPAC — International Union of Pure and Applied Chemistry ™@ Elements belonging to the same group have similar (not identical) properties Special names of some groups ™@ Group 1 — Alkali metals @ Group 2 —Alkaline earth metals ™@ Group 17 —Halogens ™ Group 18 — Noble Gases Periods @ Horizontal rows ™ Properties of elements that belong to a period show a pattern or trend that is repeated in the next period m@ Numbered 1-7 Pattern in lon Formation ™ Most elements form ions (except noble gases) ™@ Group 1 :+1 Group 15 :-3 @ Group 2: +2 Group 16 :-2 @ Group 13 : +3 Group 17 :-1 ™@ Group 14 : do not readily form ions Of the known elements, 11are gases at room temperature. four are liquids at 25°C, Hg, Br, Ga and Cs. If Fr can be prepared in large quantities, it is expected to be a liquid. Property Across a period (left to right) Down a group (top to bottom) atomic size/radius Decreasing Increasing ionization energy Increasing Decreasing affinity for electrons Increasing (upto Group 17) Decreasing Tendency to form | Decreasing Increasing Cation Tendency to form | Increasing (upto Group 17) Decreasing Anion Metallic Character Decreasing Increasing Electronegativity Increasing Decreasing Note: The size of the cation is smaller as compared to its neutral atom The size of the anion is larger as compared to its neutral atom. Atomic Size » Covalent radius — % the distance between the nuclei of two identical atoms joined by a single covalent bond. » Metallic radius — % the distance between the nuclei of 2 atoms in contact in the crystalline solid metal. lonization Energy >» Energy required to remove an e- from a gaseous atom or ion Xi > Xt & Where the atom or ion is assumed to be in its ground state Affinity for electrons 31 > Tendency of an atom or ion to attract additional e- Xq te 2X oy Electronegativity > The attraction of an atom for shared electrons. Note: Metals react with oxygen gas forming a basic oxide in water. Nonmetals react with oxygen gas forming an acidic oxide in water. CHEMICAL LANGUAGE AND SHORTHAND Chemical symbols An element is represented by a symbol which may be one or two letters; the first is capitalized and the second is in the lower case. The symbols may be derived from the Greek, German or Latin names of the elements. Binary Covalent Compounds Binary covalent compounds are formed between two non-metals A. Naming binary covalent compounds 1. Identify the elements present in the compound given by the chemical formula. The name of the more metallic element is written first. 2. Change the suffix of the less metallic element to —ide. 3. Use the prefix corresponding to the number of atoms present in the compound. Number Greek Prefix Number Greek Prefix 1 Mono- 6 Hexa- 2 Di- 7 Hepta- 3 Tri- 8 Octa- 4 Tetra- 9 Nona- 5 Penta 10 Deca- The mono- prefix is frequently omitted, particularly for well-known substances. If no prefix is use, it usually implies that no number of atoms of element is one. However, experts in nomenclature caution that this can be dangerous and suggest that it is better to include the mono- prefix. Some compounds are known only by their common names. The most common of this are: Forrmula H20 NH; PH3 Name Water Ammonia Phosphate . Writing formulas of binary compounds 1. Represent each kind of element in a compound with the correct symbol of element. 2. Indicate by a subscript the number of atoms of each element in a molecule of the compound. 3. Write the symbol of the more metallic element first. (H is an exception to this rule.) IONIC COMPOUNDS Compounds formed between metals and nonmetals are called ionic compounds. A. Naming lonic Compound 1. Write the name of the cation first, followed by the name of the anion. 2. Unlike binary covalent compounds, PREFIXES ARE NOT USE to indicate the number of ions present in the formula. 32 404g + 32009 > 36.04 g 36.04 greactants > 36.04 g products ™@ FOLLOWS THE LAW OF CONSERVATION OF MASS Balancing Chemical Equations Some important points: + Use correct chemical formulas + Adjust only the coefficients, NOT the subscripts * Balance elemental forms ( e.g. Ar, Cu, Na, O2, No, lz, Ss...) and H and O last. + Use the simplest possible set of whole no. coefficients Stoichiometry- The quantitative study of reactants and products in a chemical reaction Mole Method - The stoichiometric coefficients in a chemical equation can be interpreted as the number of moles of each substance. Steps: + Write correct chemical formulas and balance the equation. Convert the quantities into moles. Use the mole ratios to calculate moles of the required substance. Convert calculated moles to whatever units required. Three types of calculation: he Mole In 1971, at the 14" meeting of the General Conference of Weights and Measures, scientists agreed to adopt the mole as the unit of an amount of substance The mole (abbreviated mol) is the amount of substance that contains the same number of elementary particles as the number of atoms in exactly 12 grams of C-12. Ways of expressing the mole: 1. by number of particles (use Avogrado’s number, 6.02 x 10” particles per mole) 2. by mass (use molar mass) 3. by volume (use molar volume, 22.4 L at STP) Interconversions +MM x 6.02 x 10? Mass¢——_ Mole <———*"_ No. of particles x MM + 6.02 x 10% 35 The molar mass is the mass in grams of 1 mole of a substance. The molar mass is numerically equal to the atomic mass (or atomic weight) of an atom or the formula mass of a molecule, a compound or a polyatomic ion. Formula and Composition The percentage composition of a compound is a list of the percentages by weight of the elements in the compound. The percentage by weight of an element in a compound is numerically equal to the number of grams of the element that are present in 100 g of the compound Ex. What is the percentage composition of quick lime, CaO? Ans. 71.5% Ca, 28.5% O Empirical Formula- is the formula with lowest possible whole number subscripts to represent the composition of the compound. It can be determined from the % composition data. Ex. Barium carbonate, a white powder used in paints, enamels and ceramic, has the following composition: Ba, 69.58%; C, 6.090% and O, 24.03%. Determine its empirical formula Ans. BaCO; Molecular Formula- gives the actual composition or the actual number of atoms of each element present in one molecule or one formula unit of the compound Ex. Molecular formula of glucose: CeH:206 Empirical Formula of glucose: CH2O Stoichiometry of Reactions Chemical Stoichiometry- is the quantitative relationship of the amounts of reactants used and amounts of products formed in a reaction. This mass relationship is expressed in the balanced equation for the reaction. Percent yield- portion of the theoretical yield of product that is actually obtained in the reaction %yield= (actual amt of product obtained/ theoretical amt) x 100 Theoretical Yield - the amount of product that would result if all the LR reacted. - Maximum obtainable yield Actual Yield - The amount of product actually obtained from a reaction - Always less than theoretical yield Limiting reactant- reactant that is completely consumed in the reaction. It also determines the amount of products that can be formed. Excess reactant- reactant that is not completely used up in a chemical reaction TIES THAT CHEMISTRY BIND Chemical Bonds- net forces of attractions that hold atoms together Properties: ™ Bond energy — amount of energy that must be supplied to separate the atoms that make a bond ™@ Bond length — distance between 2 nuclei of 2 covalently bonded atoms ™ Bond order — number of bonds between atoms Types of Chemical Bonds a. covalent bond- pair of electrons that is shared by two atoms of nonmetals; represented by Lewis structure or electron dot formula 36 Types of Covalent Bonds: Single bond - two atoms held by one e- pair Double bond — two atoms held by 2 e pairs Triple bond — two atoms held by 3 e- pairs + Higher Bond order, shorter Bond length, higher Bond energy Polar covalent bond — one atom is more electronegative than the other atom; unequal sharing of electrons; the more electronegative atom is partially negative and the less electronegative atom is partially positive. Nonpolar covalent bond — equal sharing of electrons Coordinate Covalent Bond — the electrons being shared comes from a single atom b. ionic bond or electrovalent bond- It is the transefer of electrons from a metal to a nonmetal, i.e., the metal loses an electron while the nonmetal gains an electron converting them intro charged ions. - attraction between cations and anions c. metallic bond- the attraction between the cations in the lattice and the “sea of delocalized electrons” moving within the lattice Lewis Structure-one or a combination of Lewis symbols to represent a single atom (neutral or charged), a molecule or a polyatomic ion. - based on Octet Rule Octet rule- the observed tendency of atoms of the main block elements to lose, gain or share electrons in order to acquire an octet of electrons in their outermost main energy level It is more appropriately called Noble Gas Rule Electron Pairs could either be ™ Lone pairs — pairs of electrons localized on an atom ™@ Bonding pairs — those found in the space between the atoms Drawing Lewis Structures 1. Sum the valence electrons from all atoms (total # of e-’s) Total electrons = sum of the valence electrons of all atoms — charge 2. Determine the central atom and draw the skeletal structure. Cental atom is the most metallic atom or the least electronegative. 3. Use a pair of e-’s to form a bond between each pair of bound atoms. 4. Distribute remaining electrons to the terminal atoms to satisfy octet. 5. If there are still available electrons, put them on the central atom to satisfy octet. 6. If the central atom does not satisfy octet, move electron pair (lone pair) from the terminal atoms towards the central atom to form multiple bonds. STRICT FOLLOWERS of OCTET: C, N, O, F and H (2 electrons) 7. Check the Lewis structure. H and F are always terminal atoms and joined by a single bond. HYPERVALENT ATOM — atom that could accommodate more than the octet due to low-lying d- orbitals. RESONANCE - The use of two or more Lewis Structures to represent a particular molecule or ion. - Can be written for molecules/ions having a double or a triple bond and single bond(s). Resonance Structures- one of two or more Lewis structures for a single molecule that cannot be represented accurately by only one Lewis structure. - The true structure is the average or the “hybrid” of the resonance structures. FORMAL CHARGE- Used to evaluate non-equivalent Lewis structures (different from resonance structures) = no. of valence electron in the free state — no. of nonbonding electrons — no. of bonds 37 Stronger IMFA, higher viscosity 3. Vapor Pressure- Vapor exerted by a vapor at equilibrium with its liquid at a given temp. Stronger IMFA, lower vapor pressure 4. Enthalpy of Vaporization, AHvap- Energy that must be supplied to evaporate a liquid at 1 atm Stronger IMFA, higher AHvap 5. Boiling Point- temperature at which the vapor pressure of a liquid equals atmospheric pressure Stronger IMFA, higher boiling point 6. Freezing Point/ Melting Point- temperature at which the rate of liquid converting to solid equals the rate of solid converting to the liquid Stronger IMFA, higher FP/MP. 7. Heat of Fusion, AHfus- amount of heat required to melt a specified amount of solid at its MP Stronger IMFA, higher AHfus PHASE CHANGES AND PHASE DIAGRAMS The Kinetic Molecular Theory (KMT) Applied to gases: Gases consist of large number of particles (molecules or atoms). The gas particles are far apart. The volume therefore is negligible. The particles are in constant, random and rapid motion. They move in all directions At higher temp. the particles move faster. As the temp. of the gas increases, the ave. KE of the particles also increases. The particles are so far apart that the repulsion or attraction between them is negligible. PON> HH a KMT extended to liquids 1. Liquids consist of large number of particles. 2. These particles are close together. 3. The particles are in constant motion. Their motion is more limited compared to that in gases because of their nearness to each other but their can slip around one another. 4. The dependence between temperature and KE is the same as that in gases. 5. The particles experience attractive forces between them since they are closer to each other. KMT extended to liquids Solids like liquids and gases consist of large number of particles. 2. The particles are close together, as in liquids. The difference is that the molecules in a solid have a very well-ordered arrangement. 3. The movement of particles consist mostly of vibration within a fixed point. 4. The dependence between temp. and KE is the same as that of gases and liquids. 5. The particles experience attractive forces between them. These forces are stronger compared to that in liquids. Factors Affecting Vaporization 1. Atmospheric pressure — the lower the pressure above the liquid, the faster the rate of vaporization 2. Humidity — high humidity, slow rate of vaporization 3. Surface area —a large surface area provides more molecules the opportunity to escape 4. Motion of the atmosphere — vaporization occurs rapidly in moving air than in still air Heating Curve 40 Temperature (°C) PHASE DIAGRAM Pressure Temperature At constant temperature, phase change occurs and at _ this temperature, kinetic energy is constant while potential energy is increasing At increasing temperature, kinetic energy is increasing while potential energy is constant. @ Triple point - all 3 states are present @ Critical point: ™ Critical temp. — temp.above which the vapor cannot be liquefied no matter what pressure is applied @ Critical pressure - pressure required to produce liquefaction at the critical temp. Supercritical Fluid (SCF) ™@ Has the high density of a liquid but the low viscosity of a gas ™ Molecules in SCF, being in much closer proximity than in ordinary gases, can exert strong attractive forces on the molecules of a liquid or solid solute GASES Properties: @ Expansion Indefinite shape Compressibility Ease of mixing Low density Jan Baptista van Helmont- coined the term “chaos” or “gas” Evangelista Toricelli- showed that the air in the atmosphere exerts pressure; designed the first barometer Properties of Gases (Measurable) 1. Pressure (P)- force per unit area P= FIA Sl unit: 1 Pa= 1 N/m? Standard atmosphere : 1 atm=760 mmHg=760 torr=101325 Pa = 1.01325 bar Al 2. Volume (V)- space occupied by the gas (unit: L, mL) 1 dm?= 1b; 1cem*=1 mL 3. Temperature (T)- expressed in K, °C or °F K= °C + 273.15 Absolute zero temp= 0 K= -273.15°C > molecules stop moving Standard Temperature and Pressure (STP): 0°C, 1 atm Standard Ambient Temperature and Pressure (SATP): 25°C, | bar 4. no. of moles of gas (n) Gas Laws 1. Boyle’s Law- Robert Boyle - the volume occupied by a given mass of gas at const temp is inversely proportional to the pressure (V a 4/P) ¢ does not apply to liquids and solids ¢ applies only at moderate or low P and moderate or high T PwVi= PV 2. Charle’s Law- Jacques Charles (1746-1823) - the volume occupied by a given mass of gas at const pressure is directly proportional to temp (V aT) @ Charles is the first person to fill a balloon with hydrogen gas (Made the first solo balloon flight) Via = V2 Ti Te 3. Avogadro’s Law- Amadeo Avogadro (1776-1856) - for a gas at const T and P, V is directly related to the no. of moles of gas (V an) Molar volume- one mole of any gas at STP occupies a volume of 22.4 L Via = Ve ny m2 4. Gay-Lussac’s law- the pressure occupied by a given mass of gas at const volume is directly proportional to temp (P a T) Pi= Be Ti Ta 5. Combined gas law (PV)IT =k, hence (P1V1)/T1 = (P2V2/T2 6. Ideal Gas Law PV= nRT Where P = Pressure (atm) V = Volume (L) n =no. of moles (mol) R = Universal gas constant= 0.0821 L-atm/mol-K T = Temperature (K) Daltons’s Law of Partial Pressures ™ For a mixture of gases in a container, the total pressure exerted is the sum of the pressures that each gas would exert if it were alone. Praat = Pi + P2 + Ps +... + Pr @ Where P,, P2 and P; are partial pressures of the gas each gas would exert if it were alone in the container. 42 pH = -log [H30*] pOH = -log [OH] pH + pOH = 14 Strong Acids @ HCl HBr @ Hi HClO, m@ HNO; H2SO, (1st ionization only) Strong Bases ™@ Hydroxides of Groups 1 and 2 Weak Acids and Bases —ionizes to small extent The larger the Ka (ionization constant of acid), the stronger the acid, greater [H30*] The larger the Kb (ionization constant of base), the stronger the base, greater [OH] Lewis Definition (Gilbert Newton Lewis, 1875-1946) ™ Base -a substance that can donate an e pair ™ Acid —a substance that can accept an e- pair Titration - aneutralization reaction - a solution is gradually added to another solution until the solute of the first solution has completely reacted with the solute of the second solution Indicator — an organic compound that changes color depending on the pH e.g. phenolphthalein colorless — acidic faint pink — neutral pink — basic Equivalence Point- the point at which the solute of the first solution has completely reacted with the solute of the other solution Endpoint — approximates the equivalence point. It is very close to the equivalence point. Standardization — it is the process of determining the concentration of a solution using a standard solution. The solution has a known concentration. Titrant- the solution usually placed on the buret. This is usually the solution of known concentration. Analyte- the solution of unknown concentration usually placed in the Erlenmeyer flask. BUFFERS - Asolution that resists drastic changes in pH when small amounts of acids or bases are added. Components: > Aweak acid and its conjugate base (in salt form) OR > Aweak base and its conjugate acid (in salt form) pKa =-log Ka pKb =- log Kb Henderson-Hasselbach equation: pH = pKa + log [baseJ/[acid] CHEMICAL EQUILIBRIUM - The state in which the forward and backward reactions continue to occur but the concentrations of all reactants and products remain constant with time. Characteristics: 1. Dynamic Situation — the forward and backward reactions continue to exist 2. Balance - the rate of forward reaction is equal to the rate of backward reaction AS 3. Law of Mass Action — reactions in equilibrium can be expressed in a Definite Mathematical Expression For a general equation: aA+bB g——* cC+aD Keg = [C]° [D]*/ [A}*[B}? where Keq is the equilibrium constant [] molar concentration In the expression, only aqueous and gaseous substances are included. Solids and liquids are not included since their concentrations are relatively constant. Keq = Ke Ke is the equilibrium constant when substances are expressed in molar concentration Kp = Ke (RT)*9 Kp is the equilibrium constant when substances are expressed in their partial pressures R is the universal gas constant and T is the temperature in Celsius Ang is the difference between the number of moles of gaseous particles of products and reactants Keq > 1, at equilibrium, reaction system consist mostly of products -shift to the right - very large Keq: reaction goes to completion Keq <1, at equilibrium, reaction system consist mostly of reactants -shift to the left - reaction does not occur to a significant extent Le Chateler’s Principle -Henry Louis Le Chatelier (1850-1936) - If a change in conditions (a “stress’) is imposed on a system at equilibrium, the equilibrium position will shift in a direction that tends to reduce that change in conditions. Factors Affecting Equilibria 1. Change in concentration - If a reactant or product is added to a system at equilibrium, the system will shift away from the added component. - If a reactant or product is removed, the system will shift toward the removed component. 2. Change in pressure > affects only system involving gases Three ways to change the pressure of gaseous systems at a given temperature: a. Add or remove a gaseous reactant or product at constant volume- same effect as change in concentration b. Add an inert gas (not involved in the reaction) at constant volume — increase in total pressure but has no effect on concentrations or partial pressures of the reactants or products c. Change the volume of the container — when the volume of the container holding a gaseous system is reduced, the system responds by reducing its own volume. This is done by decreasing the total no. of gaseous molecules in a system 3. Change in temperature 1. Keq value changes with temperature 2. Energy is treated as a reactant (endothermic) or product (exothermic) 3. If energy (heat) is added, the equilibrium will shift to the direction which consumes the added energy 46 4. Catalyst - Speeds up both the forward and backward reactions - Equilibrium is achieved more rapidly but the equilibrium amounts are unchanged - Therefore, has no effect on equilibria CHEMICAL KINETICS ™@ The area of chemistry concerned with the speeds or rates at which a chemical reaction occurs Collision Theory- Chemical reactions occur as a result of collisions between reacting molecules. ™ For a reaction to procede, reacting particles must collide effectively to enable outer shell electrons to interact. ™ Collisions to be effective, must be with enough energy to overcome repulsive forces between electrons surrounding the nuclei of atoms. Activation Energy (Ea) ™@ The threshold energy that must be overcome to produce a chemical reaction Transition State or Activated Complex ™ A temporary species formed by the reactant molecules as a result of the collision before they form the product. FACTORS AFFECTING REACTION RATES 1. Concentration — higher concentration, higher reaction rate; more molecules, more collisions 2. Temperature - Higher temperature, more collisions with high energy, higher reaction rate 3. Catalyst - Asubstance that increases the reaction rate without itself being consumed. - hastens the reaction by providing a path with lower activation energy thus less energy is needed for a reaction to proceed 4. Pressure - affects gaseous systems - higher pressure, more collisions; higher reaction rate THERMOCHEMISTRY + Study of heat changes in chemical reactions + Thermal energy transferred between 2 bodies that are at different temperatures + Units: 1 calorie = 4.184 J System > A specific part of the universe that is of interest Surrounding > The rest of the universe outside the system Exothermic Process : Q= (-) - Heat is transferred from the system to the surroundings Endothermic Process: Q = (+) - Heat is transferred from the surroundings to the system LAW OF THERMODYNAMICS 1. First Law of Thermodynamics - Energy can be converted from one form to another, but cannot be created nor destroyed. 2. Second Law of Thermodynamics - In any spontaneous process, there is always an increase in the entropy (disorder) of the universe AT Where - boundary between different phases (e.g. electrode and solution) |- boundary between half-cell compartments (e.g. salt bridge) Mnemonics: ABC > anode- bridge- cathode CELL POTENTIAL / CELL VOLTAGE / ELECTROMOTIVE FORCE (emf or E) + The difference in electrical potential between the anode and the cathode + Higher cell potential, higher energy given off by e-’s, strong tendency to generate electric current * 1 volt = 1 joule / 1 coulomb © 1V=1J/C + Energy (J) = charge(C) x cell potential (V) E° cell > positive > spontaneous process For reactions in which reactants and products are in their standard states, AG? = -nFE°cell AG° E°cell Spontaneity - + spontaneous 0 0 at equilibrium + - non-spontaneous Note: Higher reduction potential> higher tendency to undergo reduction Higher oxidation potential> higher tendency to undergo oxidation Electrolytic Cell + Electrical energy is used to cause a non-spontaneous chemical reaction to occur + ELECTROLYTIC CELL is the apparatus used. 1. Two electrodes share the same compartment 2. Hasa single electrolyte 3. The conditions are usually far from the standard : gas pressures are rarely close to 1 atm and solutions are not 1M. Battery withdraws e-’s from the anode and pushes them to the cathode. Anode > where oxidation occurs; positive Cathode > where reduction occurs; negative Electron flows from anode to cathode Anions go to the anode and cations go to cathode E°cell is negative > non-spontaneous CORROSION > conversion of metal to its metal oxide Rusting — corrosion of iron ORGANIC CHEMISTRY - _ study of carbon and its compounds; chemistry of the hydrocarbons (compounds containing only carbon and hydrogen) and their derivatives. Hydrocarbons: 1. Alkane — CrHan+2 - all single bonds 2. Alkene — C,Hon - double bond between carbon and hydrogen is present 3. Alkyne — CnHa -2 - triple bond between carbon and hydrogen is present 50 Aromatic > cyclic derivative Aliphatic > open-chain Oxygen Containing 1. Alcohol (R-OH) 2. Ethers (R-O-R) 3. Carboxylic Acids (RCOOH) 4. Esters (RCOOR) 5. Aldehydes (RCOH) 6. Ketone (RCOR) Others: 1. alkyl halides (RX) where X is either F, Cl, Br, | 2. amines (RNH2) 3. amides (RCONH:) NOMENCLATURE OF ALKANES Alkanes are named by the IUPAC (International Union of Pure and Applied Chemistry) system, which uses a systematic set of rules. Many also have non-systematic common or trivial names that are still in use. Common Names At a time when relatively few organic compounds were known, it was customary to name new compounds at the whim of their discoverers. Urea was so named because it was isolated from urine. Morphine, a painkiller, was named after Morpheus, the Greek god of dreams. Barbituric acid, a tranquilizer, was named by its discoverer after his friend Barbara. These older names for organic compounds are now called common or trivial names; many of these names are still widely used in the chemical literature and in commerce. In the common nomenclature, the total number of carbon atoms in an alkane, regardless of their arrangement, determines the name. The first three alkanes are methane, ethane and propane. For alkanes beyond propane, certain prefixes are used to differentiate the different structural isomers. = The prefix normal or n- is used to indicate that all carbons are joined in a continuous chain. = The prefix iso- is used to indicate that one end of an otherwise continuous chain terminates in a (CH3)2CH- group = The prefix neo- is used to indicate that one end of an otherwise continuous chain terminates in (CHs)sC- group THE IUPAC System The system of nomenclature so devised is presently known as the IUPAC system. Systematic names or organic compounds consist of three main parts: Prefix — stem — suffix The stem indicates the number of carbon atoms in the backbone or parent chain of the molecules. The parent chain is the longest continuous chain of carbon atoms. Backbone Stem Backbone Stem Ci Met- Cu Undec- Co Eth- Ci2 Dodec- C3 Prop Cis Tridec- Cy But- Crs Tetradec- Cs Pent- Cis Pentadec- Ce Hex- Cre Hexadec- Cr Hept- Cuz Heptadec- Ce Oct- Crs Octadec- Sl Co Non- Cro Nonadec- Cro Dec- Co Eicos- The suffix identifies the type or class of the compound. For alkane, the suffix is —ane. Attached to the backbone are the side-chains or substituents. The substituents present are indicated by the prefix. In alkanes, the side-chains are called alkyl groups, which are derived from alkanes through the removal of one hydrogen atom. They are named by changing —ane ending of the parent alkane to —yl. Steps: 1. Locate the parent chain a. Find the longest continuous chain present in the molecule and use the name of that chain as the parent name. b. If there are two different chains of equal length, choose the one with the larger number of branch points as the parent chain. 2. Number the carbon atoms in the parent chain so that the substituents are given the lowest position numbers. 3. Identify the substituents and the position of the carbon atoms to which they are attached. a. If there are two substituents on the same carbon, assign them both the same number. b. There must always be as many numbers in the name as there are substituents. 4. Write the name of the compound by first arranging all substituents in alphabetical order and preceeding the name of each substituent by the position number and then adding the name of the parent chain; use hyphens to separate the different prefixes and commas to separate numbers. a. If the same alkyl group occurs more than once as a substituent, indicate by prefixes di-, tri-, tetra-, etc. However, do not use these prefixes for alphabetizing purposes. 5. Prefixes such as cyclo, neo- and iso- are included in alphabetizing substituents, while hyphenated prefixes such as tert-, sec-, n- are ignored. °9 Hac yoH CGHe CHe CHe GH CH2 CHe HC 3 Hz 2,6-dimethyloctane For alkenes The same as alkanes with some modifications: a. The parent chain must contain the double bond. b. The parent chain is named by changing the —ane ending of the corresponding alkane to -ene and indicating the position of the double bond by the lowest number possible. c. The carbons bearing the substituents are also given the lowest numbers possible, but the double bonds takes precedence. For alkynes The rules are the same as for naming of alkenes, except that the ending -yne replaces -ene Biochemistry Polymers Building Blocks Protein amino acids Carbohydrates monosaccharides Nucleic Acids nucleotides Lipids fatty acids + glycerol Saccharides — Sugars Monosaccharide > one unit Disaccharide > two units of monosaccharide 52 B. Mechanics Motion — change in position of an object relative to other objects that are considered at rest. e Linear Motion Distance vs. Displacement Distance — total path length traveled by a body. Displacement — change in position of an object. It represents the straight line path between the starting and end points. Example: a. Jen travels Skm to work and back. What is the distance she travels? What is the displacement? Distance = Skm + Skm = 10km Displacement = 5km — 5km =0 *since there is no change in position, her displacement is zero b. Rocky walks 20 km due north from his camp. Late in the afternoon, he walks back 11km south along the same path. i. What is his total displacement from the camp? ii. What is the total distance he traveled? i. Displacement = 20km + (-11km) = 9km due north ii. Distance = 20km + 11km = 31 km Speed vs. Velocity Speed — measure of how fast an object travels o Average speed — ration of total distance traveled to the time needed to cover that distance. TotalDis tan ceTravelled Average Speed = geSpe' ElapsedTime Example: It takes a school bus 1 hour to travel 20km. What is its average speed? 20km km AverageSpeed = —— = 20 — gene lhr hr o Instantaneous speed —is the speed at particular instance in time 55 —*2 =” Instant speed = “* instantaneous eed =—— = P At t,-4, Example: What is the speed of a car that covered 150km in two hours? Ax _ 150km—0 kn Instantaneous Speed = av _ ioe = 75 Am At 2hrs —0 hr o Velocity — rate of motion with direction displacement Velocity = aepiacement time Example: Rocky drives a distance of 80km in 2 hours towards the north direction. What is his velocity? Solution: _ 80km 2hrs v v=40 km north hrs o Acceleration — rate of change of velocity ChangeOfvVelocity time Acceleration= . ae . km km . Example: A driver steadily increases his velocity from 307 to 607 in 2 hours. What is his acceleration? 60 39 Am lin ___Ar hr eae 2hrs hr* Graphs relating displacement, velocity and acceleration 56 Where Zero acceleration, Zero velocity x= displacement velocity cceleration S7 c) Freefall - a good example of uniform accelerated motion - one dimensional motion where the moving object is only under the influence of gravity - gravitational acceleration is equal to -9.8m/s? V,=V.t8t yey, +p t+8h oth ft V7=V 2+ 23aY AY=(V,+ Vit 2 Where: V; = final velocity Vo = initial velocity g =-9.8m/s?, gravitational acceleration t=time inal position initial position AY =Y—-Yo, displacement Example: A ball is dropped from a building without an initial velocity. Find the velocity of the ball after 5 seconds. Find: V; Solution: Vr= gt = (-9.8m/s’) 5s =-49m/s Example: A mango falls from a tree. How far does it fall after 0.5 seconds? Given: t=05s Vo=0 Find: AY Solution: st 9 AY=[7,t+ AY =-19.6m 60 d) Projectile Motion — curved motion of an object that is projected into the air and acted upon by the gravitational force of the earth - a combination of uniform motion and freefall Projectile — an object thrown into the air that is allowed to move freely and is influenced only by gravity RANGE Range — horizontal distance covered by a projectile Time of flight — time in which the projectile is up in the air Trajectory — curve traced by the path of the projectile Maximum height, h —the vertical displacement traveled by the projectile in its trajectory Conditions of Projectile Motion throughout the flight: a) Neglect the effect of air resistance to the body b) The horizontal and vertical motions are independent of each other. Separate the displacement and velocity to its x and y components. Along the horizontal: i) the x component of the velocity is constant throughout the flight ii) the horizontal displacement x, follows uniform motion iii) Formula along the horizontal is the same as uniform motion Along the vertical: i) the y component of the velocity acts as freefall and thus, only affected by the gravitational acceleration ii) The velocity’s sign is positive (+) for upward motion while for downward motion, it is negative (-). iii) Upon hitting the ground, its velocity is always equal to zero. iv) The time required for the projectile to reach its maximum height from its firing point is equal to the time that the projectile will reach the same height of its firing point from the maximum height. v) Formula along the vertical is the same as freefall 61 When vertical displacement is at its maximum height: i) the x component of the velocity is constant ii) the y component of the velocity is equal to zero iii) the acceleration is still equal to g,-9.8m/s? Example: A stone is thrown with an initial horizontal velocity of 10m/s from the top of a tower 200m high. Where is the stone after 2s? When will it hit the ground? What is its speed just before it hits the ground? Given: Vx = 10m/s dy = 200m t=2s Find: dx after 2s, t, Vf Solution: i) Ax=vt Ax = (10m/s)(2s) Ax = 20m Since there is no initial velocity along the vertical and the top of the building is the reference point, Yo and Vyo is equal to zero. ili) V,=V,+8t V ,=0+€9.8m/ s°)(6.38s) V ,=-62.52m/s C. Newton's Laws of Motion - explains why objects move, and define the relationship between the external forces acting on a body — as well as between two or more interacting bodies and the motion that arises from the action of these forces. 1. First Law of Motion (Law of Inertia) “Every material continues to be at rest if it is at rest or in uniform motion if it is in motion, unless it is compelled to change that state by forces acted upon it.” Inertia —is the tendency of an object to resist a change in its state of motion Mass —is a measure of an object's inertia 62 Collision — any string interaction between two bodies that lasts a relatively short time Two types of Collision i) Elastic collision — after the collision, the objects is still separatd from each other ii) Inelastic collision — after the collision, the objects move as one unit External Forces — Forces exerted on any part of the system by any body outside the system E. Work, Energy, Power Work — the product of force and displacement W = Fe Axcosé Where: W = work F = force Ax = displacement NOTE: A force does no work if it is perpendicular to the displacement Example: A 100N block lies on a frictionless surface. A force of 20N was applied horizontally where the block had moved 5m. Find the work done by the force and weight of the block. Given: Weight of the block = 100N Force applied = 20N Displacement = 5m Find: Work by the force and weight Solution: OW sence =F eAxcosé W sone = 20N ¢Smcos0 W pre = 100Nm =100Joules 1) WV sei = F * Avcos8 We scoien = 100° Ocos 90 weight W veict =0 The work done by the weight is equal to zero since it is perpendicular to the displacement. Energy — capacity to do work - a scalar quantity Types of Mechanical Energy a) Potential Energy — The energy stored on an object due to its position. i) Gravitational Potential Energy PE ray = mgh Where: 65 b) ii) PE = Potential Energy m = mass g = gravitational acceleration h = height Elastic Potential — energy stored on an elastic material due to its stretching or compressing PE. = ZkAx Where: PE = Potential Energy k = force constant of the spring Ax = extension/compression of the spring Kinetic Energy — energy of an object in motion KE =3m v Where: KE = Kinetic energy m = mass v= velocity 66