Download The Nature of Things - Introduction to Physics Survey | PHYS 1030 and more Study notes Physics in PDF only on Docsity! Chapter 2 The nature of things The Greeks thought about the nature of matter. Matter can be described as the substance of which physical materials are composed of. Examples of material substances such as wood, ice water, sausage, gold… All of these are composed of matter. What do different types of substances have in common with each other? One idea is that all matter can be divided up into smaller pieces. Do this enough and eventually you would get to pieces so small they are no divisible. The Greeks called these particles: atoms. Water Water is made up of hydrogen and oxygen, so water cannot be an element. Substances made up of more than one element are called chemical compounds. Water H2O Salt NaCl Chemical compounds can be split up into smaller and smaller pieces. The smallest particles of a compound that still retains the properties of the compound is called a molecule. Some elements are made up of two-atom molecules. For example hydrogen gas is made up of two hydrogen atoms. hydrogen gas H2 This is called a diatomic molecule. Quantitative – measurement using numbers to describe situation. Car drives 100 mph. It’s 1000F outside. Qualitative – description without numbers The car is fast. It’s hot. Macroscopic – phenomena that can be easily observed. Occurs on a ‘large’ scale. Temperature is macroscopic. When you smell something, a macroscopic observation occurs. Microscopic – occurs on a very small scale. An unseen level for humans. The speed of the individual atoms that results in the given temperature is microscopic. The atoms that produce the smell can be studied microscopically. Section on making estimates It can be useful to learn how to make wise estimates to find an approximate answer to many questions. This is useful when no calculator is handy or you really don’t care about the exact amount. Estimations and order of magnitude calculations Estimate the number of people needed to make ‘human chain’ across Tennessee. TN is about 500 miles long 1 mile about 1.6 km So TN is about 800 km long. Reach of a person is about 1 meter. 800km is 800*1000 meters. You would need about 800 000 people. Atomic models. Greek model – atoms was an unchanging atom, like a tiny solid ball. Some experiments disproved this idea. Planetary model – electrons orbit around a central nucleus made up of protons and neutrons. In the 1920’s new experiments involving electrons contradicted this idea. Quantum theory of the atom. So far has not been disproved. We will discuss this much later.
