Department of Chemistry CHEM1010 General Chemistry *********************************************** Instructor: Dr. Hong Zhang Foster Hall, Room 221 Tel:

CHEM1010/General Chemistry _________________________________________ Chapter 1. (L2)-Introduction Today’s Outline..We recognize many things are different..How to tell one kind of matter from another kind?..How to distinguish between things in a scientific way?..Properties of matter..Classification of matter

Chapter 1. (L2)-Introduction We recognize many things are different In the last lecture, we discussed that people recognize that many things around us are different (lakes, rocks, soils, trees, metals, ……) We can’t help asking questions like How are things different? (lake water, seawater) Why are things different? (Why is sea water salty?) Can we predict changes of things? (Will my garden soil still be good next year if I don’t apply lime this year?)

Chapter 1. (L2)-Introduction How to tell one kind of matter from another kind? Let’s take a look at language first. We observe: Words are different. For example: accomplishments, hot (long vs. short) sun, pun, fun (1 st letter different) pot, top (same letter composition, different sequence of letters) work (n), work (v) (function different) Water, WATER (case different)

Chapter 1. (L2)-Introduction How to tell one kind of matter from another kind? We have observed: Words have a number of characteristics, for example: composition size sequence of letter function case and more

Chapter 1. (L2)-Introduction How to tell one kind of matter from another? Just like words, things or matter also have a number of characteristics as we intuitively recognize with our common senses, for example: heavy, light (coin, paper bill) large, small (gemstone) durable, non-durable (cotton, nylon) solid, gas, liquid (ice, steam, water) color (coal, gold, silver) hard, soft (stone, sponge) and more

Chapter 1. (L2)-Introduction How to tell one kind of matter from another? Now, probably you already naturally come to this finding: Things or matter differ because of their differences in one or more of their characteristics or properties. Now, we ask this question: What are the characteristics or properties of matter or things we use to distinguish between them?

Chapter 1. (L2)-Introduction How to distinguish between things in a scientific way? In science, we want to be accurate, as much as possible. That means, we need to find out the properties that we can handle accurately. So, we can tell exactly how two things are different. Quiz Time Which of the following characteristics of things is the one we can handle accurately? (a) history, (b) beauty, (c) size, (d) usefulness

Chapter 1. (L2)-Introduction How to distinguish between things in a scientific way? We also noticed, intuitively, some properties of things share some common features. For example First category: ice, steam, liquid water hot and cold aluminum foil thick and thin aluminum foil Second category: If you burn a piece of paper, then you got ash Iron turns to be rusty

Chapter 1. (L2)-Introduction How to distinguish between things in a scientific way? What’s the difference between the two categories? For the first category, the material does not change. But, for the second category, the material changes.

Chapter 1. (L2)-Introduction Properties of matter In science, we distinguish between things by two categories of properties: Physical properties -those reflecting certain differences without any change of the material Chemical properties -those reflecting certain changes of materials (or in other words, chemical composition)

Chapter 1. (L2)-Introduction Properties of matter Common physical properties: Mass Size (length, wideness, height, volume) Temperature Color Hardness (diamond, glass; aluminum, steel) Density (iron, wood) Freezing point (water, salty water) Boiling point (water, gasoline) Heat capacity (metal, water)

Chapter 1. (L2)-Introduction Properties of matter Typical chemical properties for some substances: Iron: easy to get rusty Carbon: easy to burn Teflon: inert Baking Soda: easy to remove acids

Chapter 1. (L2)-Introduction Properties of matter..Now we have these properties of matter, so if one matter is different from the other, there must be a difference in at least one property...That is, now, scientifically, we use the properties of matter to distinguish between things...Since we can handle the properties of matter accurately, we can distinguish between things accurately. We don’t say “kind of” or “sort of” or “somewhat” or “a little bit”, and so forth.

Chapter 1. (L2)-Introduction Classification of matter We have noticed there are many many different matter or materials or substances. Now, we are asking this question: Can we group different things under various categories? In other words, we want to classify things.

Chapter 1. (L2)-Introduction Classification of matter Let’s do some preliminary classification. We recognize, intuitively, some things are pure, but others are not pure, in other words, they are mixtures of pure substances. So, let’s first divide things into two basic categories:.Pure things, called substances, which contain only one kind of substances.Non-pure things: called mixtures, which contain different substances mixed up together

Chapter 1. (L2)-Introduction Classification of matter Quiz Time 1. Which of the following is a pure substance? (a) milk; (b) snow, (c) coke, (d) table salt 2. Which of the following is a mixture? (a)baking soda, (b) flour, (c) soil, (d) aluminum foil

Chapter 1. (L2)-Introduction Classification of matter Another way to classify things are based on the state of matter. We recognize the states of matter: Gas Liquid Solid Quiz Time Which of the following is a liquid material? (a) Propane; (b) boiled egg, (c) flour, (d) vinegar