CBSE Class 10 Science Notes Chapter 3 Metals And Non-Metals:, Study Guides, Projects, Research of Family and Consumer Science

Download CBSE Class 10 Science Notes Chapter 3 Metals And Non-Metals: and more Study Guides, Projects, Research Family and Consumer Science in PDF only on Docsity! Class 10 Science Notes Chapter 3 Metals And Non-Metals: In a periodic table, all elements found on the planet have been appropriately ordered based on their increasing atomic numbers. There are a total of 118 elements known to us, 92 of which are derived naturally and the remaining 26 are created artificially in the laboratory. Based on their physical and chemical properties, these elements can be divided into three groups: Metalloids, Metals, and Non-Metals. Physical Properties Any measurable property whose value describes a condition of a physical system is referred to as a physical property.A system’s physical properties can be utilised to characterise its transitions between brief states. Observables are a term used to describe physical qualities. Physical Properties of Metals ● Hard and have a high tensile strength – Carbon is the only non metal with very high tensile strength. ● Solid at room temperature – One non-metal, bromine, is a liquid at room temperature. The other non-metals are solids at room temperature, including carbon and sulfur. ● Sonorous – Metals produce a typical ringing sound when hit by something. ● Good conductors of heat and electricity – Graphite is good conductor of heat and electricity. ●Malleable, i.e., can be beaten into thin sheets ● Ductile, i.e., can be drawn into thin wires ● High melting and boiling points (except Caesium (Cs) and Gallium (Ga)) – Graphite, a form of carbon (a non-metal), has a high boiling point and exists in the solid state at room temperature. ● Dense, (except alkali metals). Osmium – highest density and lithium – least density ● Lustrous – Metals have the quality of reflecting light from their surface and can be polished e.g., gold, silver and copper. Iodine and carbon are non-metals which are lustrous. Note that carbon is lustrous only in certain forms like diamond , and graphite. ● Silver-grey in colour, (except gold and copper) – Metals usually have a silver or grey colour. Non-Metals Nonmetals are those elements which do not exhibit the properties of metals. Physical Properties of Non-metals ● Occur as solids, liquids and gases at room temperature ● Brittle ● Non-malleable ● Non-ductile ● Non-sonorous ● Bad conductors of heat and electricity Exceptions in Physical Properties ● Alkali metals (Na, K, Li) can be cut using a knife. ● Mercury is a liquid metal. ● Lead and mercury are poor conductors of heat. ● Mercury expands significantly for the slightest change in temperature. ● Gallium and caesium have a very low melting point. ● Iodine is non-metal but it has lustre. ● Graphite conducts electricity. ● Diamond conducts heat and has a very high melting point. Examples of Non-metals 1. Hydrogen – Gas 2. Nitrogen – Gas 3. Oxygen – Gas 4. Fluorine – Gas 5. Chlorine – Gas 6. Bromine – Liquid 7. Iodine – Solid 8. Carbon – Solid 9. Sulphur – Solid 10. Phosphorous – Solid 11. Silicon – Solid Chemical Properties Chemical Properties of Metals ● Alkali metals (Li, Na, K, etc) react vigorously with water and oxygen or air. ●Mg reacts with hot water. ● Al, Fe and Zn react with steam. ● Cu, Ag, Pt, Au do not react with water or dilute acids. Reaction of Metals with Oxygen (Burnt in Air) Metal oxide is formed when metals are burned in air and react with oxygen in the air. Metal oxides are a type of basic material found in nature. They change the colour of red litmus to blue. To avoid Ag Silver Au Gold Pt Platinum Roasting Converts sulphide ores into oxides on heating strongly in the presence of excess air. It also removes volatile impurities. 2ZnS(s)+3O2(g)+Heat→2ZnO(s)+2SO2(g) Calcination Converts carbonate and hydrated ores into oxides on heating strongly in the presence of limited air. It also removes volatile impurities. ZnCO3(s)+heat→ZnO(s)+CO2(g) CaCO3(s)+heat→CaO(s)+CO2(g) Al2O3.2H2O(s)+heat→2Al2O3(s)+2H2O(l) 2Fe2O3.3H2O(s)+heat→2Fe2O3(s)+3H2O(l) Reaction of Metals with Water or Steam Aluminium, iron, and zinc are metals that do not react with either cold or hot water. However, when they come into contact with steam, they produce metal oxide and hydrogen. Lead, copper, silver, and gold are metals that do not react with water. Metal+Water→Metalhydroxide or Metaloxide+Hydrogen 2Na+2H2O(cold)→2NaOH+H2+heat Ca+2H2O(cold)→Ca(OH)2+H2 Mg+2H2O(hot)→Mg(OH)2+H2 2Al+3H2O(steam)→Al2O3+3H2 Zn+H2O(steam)→ZnO+H2 3Fe+4H2O(steam)→Fe3O4+4H2 Reaction of Metals with Acid When a metal is immersed in acid, it becomes smaller and smaller as the chemical process consumes it. Gas bubbles can also be detected at the same moment. Hydrogen gas bubbles are formed as a result of the reaction. Because hydrogen is combustible, this can be demonstrated with a burning splint. Metal+diluteacid→Salt+Hydrogengas 2Na(s)+2HCl(dilute)→2NaCl(aq)+H2(g) 2K(s)+H2SO4(dilute)→K2SO4(aq)+H2(g) Only Mg and Mn, react with very dilute nitric acid to liberate hydrogen gas. Mg(s)+2HNO3(dilute)→Mg(NO3)2(aq)+H2(g) Mn(s)+2HNO3(dilute)→Mn(NO3)2(aq)+H2(g) Displacement Reaction A more reactive element displaces a less reactive element from its compound or solution. How Do Metals React with Solution of Other Metal Salts A more reactive metal can displace a less reactive metal from its salt solution in a displacement reaction. Metal displacement reaction is a common name for this reaction. The reactivity of certain regularly used metals has been ordered in decreasing order. This is referred to as the reactivity or activity series. Metal A+Salt of metal B→ Salt of metal A + Metal B Fe(s)+CuSO4(aq)→FeSO4(aq)+Cu(s) Cu(s)+2AgNO3(aq)→Cu(NO3)(aq)+2Ag(s) ● It’s a component of thermite welding. Aluminium displaces iron from its oxide in this process. ● It is used in the production of steel. In which iron is displaced from its oxide by carbon. ● It is mostly utilised in metal extraction. Reaction of Metals with Bases The base has a bitter taste and a slippery texture. A base dissolved in water is called an alkali. When chemically reacting with acids, such compounds produce salts. Bases are known to turn blue on red litmus paper. Base+metal→ salt+hydrogen 2NaOH(aq)+Zn(s)→ Na2ZnO2(aq)+H2(g) 2NaOH(aq)+2Al(s)+2H2O(l)→ 2NaAlO2(aq)+2H2(g) Extraction of Metals and Non-Metals Applications of Displacement Reaction Uses of displacement reaction 1. Extraction of metals 2. Manufacturing of steel 3. Thermite reaction: Al(s)+Fe2O3(s)→ Al2O3+Fe(molten) The thermite reaction is used in welding of railway tracks, cracked machine parts, etc. Occurrence of Metals Most of the elements, especially metals occur in nature in the combined state with other elements. All these compounds of metals are known asminerals. But out of them, only a few are viable sources of that metal. Such sources are called ores. Au, Pt – exist in the native or free state. Extraction of Metals The process of extracting metal ores buried deep underground is called Mining. The metal ores are found in the earth’s crust in varying abundance. The extraction of metals from ores is what allows us to use the minerals in the ground! The ores are very different from the finished metals that we see in buildings and bridges. Ores consist of the desired metal compound and the impurities and earthly substances called Gangue. The Why Questions Electronic Configuration Group 1 elements – Alkali metal Element Electronic Configuration Lithium(Li) 2,1 Sodium(Na) 2,8,1 Potassium(K) 2,8,8,1 Rubidium(Rb) 2,8,18,8,1 Group 2 elements – Alkaline earth metals Element Electronic Configuration Beryllium(Be) 2,2 Magnesium(Mg) 2,8,2 Calcium(Ca) 2,8,8,2 Stronium(Sr) 2,8,18,8,2 How Do Metals and Nonmetals React Metals lose valence electron(s) and form cations. Non-metals gain those electrons in their valence shell and form anions. The cation and the anion are attracted to each other by strong electrostatic force, thus forming an ionic bond. For example: In calcium chloride, the ionic bond is formed by opposite-charged calcium and chloride ions. The calcium atom loses 2 electrons and attains the electronic configuration of the nearest noble gas (Ar). By doing so, it gains a net charge of +2. The two Chlorine atoms take one electron each, thus gaining a charge of -1 (each) and attain the electronic configuration of the nearest noble gas (Ar). Ionic Compounds Ionic compounds are neutral compounds that are made up of positively charged cations and negatively charged anions. Binary ionic compounds (ionic compounds containing only two types of elements) are named by first writing the name of the cation, then the name of the anion. The electrostatic attractions between the oppositely charged ions hold the compound together. Example: MgCl2, CaO, MgO, NaCl, etc. Properties of Ionic Compound Ionic compounds 1. Are usually crystalline solids (made of ions). 2. Have high melting and boiling points. 3. Conduct electricity when in an aqueous solution and when melted. 4. Are mostly soluble in water and polar solvents. Physical Nature Ionic solids usually exist in regular, well-defined crystal structures. Most ionic compounds is soluble in water due to the separation of ions by water. This occurs due to the polar nature of water. For example, NaCl is a 3-D salt crystal composed of Na+ and Cl− ions bound together through electrostatic forces of attraction. When a crystal of NaCl comes into contact with water, the partially positively charged ends of water molecules interact with the Cl− ions, while the negatively charged end of the water molecules interacts with the Na+ ions. This ion-dipole interaction between ions and water molecules assists in the breaking of the strong electrostatic forces of attraction within the crystal and ultimately in the solubility of the crystal. Corrosion Alloys Alloys are homogeneous mixtures of metal with other metals or nonmetals. Alloy formation enhances the desirable properties of the material, such as hardness, tensile strength and resistance to corrosion. Examples of a few alloys: Brass: copper and zinc Bronze: copper and tin Solder: lead and tin Amalgam: mercury and other metal Corrosion Gradual deterioration of material usually a metal by the action of moisture, air or chemicals in the surrounding environment. Rusting: 4Fe(s)+3O2(from air)+xH2O(moisture)→2Fe2O3. xH2O(rust) Corrosion of copper: Cu(s)+H2O(moisture)+CO2(from air)→CuCO3.Cu(OH)2(green) Corrosion of silver: Ag(s)+H2S(from air)→Ag2S(black)+H2(g) Prevention of Corrosion Prevention: 1. Coating with paints or oil or grease: Application of paint or oil or grease on metal surfaces keep out air and moisture. 2. Alloying: Alloyed metal is more resistant to corrosion. Example: stainless steel. 3. Galvanization: This is a process of coating molten zinc on iron articles. Zinc forms a protective layer and prevents corrosion. 4. Electroplating: It is a method of coating one metal with another by the use of an electric current. This method not only lends protection but also enhances the metallic appearance. Examples: silver plating, and nickel plating. 5. Sacrificial protection: Magnesium is more reactive than iron. When it is coated on articles made of iron or steel, it acts as the cathode undergoes a reaction (sacrifice) instead of iron and protects the articles. Frequently Asked Questions on Metals and Non-Metals A student performs an experiment in which he dipped a copper coil to the silver nitrate solution. What will be observed from this experiment? Gray colored layer of silver appears on the surface of the copper coil. A student performs an experiment of burning magnesium ribbon in the air. A chemical reaction takes place and as a result, a white powder X forms along with a bright white light. Does the aqueous solution of changing the color of litmus paper too? Oxides of metals like magnesium are basic in nature. Therefore, aqueous solution will change the red litmus to blue. The atomic number of two elements A and B are 12 and 8 respectively. What type of compound is formed when they combine? The compound formed is AB which is ionic in nature. As we know, an ionic compound is a chemical compound in which ions are held together by electrostatic force. The electronic configuration of two elements A and B are 2, 8, 2, and 2, 6 respectively. From their electronic configuration, we see that A (magnesium) is a metal and B (oxygen) is a non-metal, thereby A loses its valence electrons and forms a cation while B accepts those electrons and forms an anion. These oppositely charged ions are drawn closer due to electrostatic forces and an ionic compound (MgO) is formed.