 Substances – matter that has a uniform and unchanging composition  Atoms and Compounds like table salt, sugar, CO2  Physical properties can be observed without changing the sample’s composition  Color, texture, density, melting point  Chemical properties are the result when a sample composition is altered  Color “changes”, rusting, odor Matter – Properties and Changes (chapter 3)

 Solids  Liquids  Gases States of Matter

 Mass cannot be created nor destroyed. Consider the following decomposition reaction 2 H2O2  2 H2O + O2 If 72 grams of water and 64 grams of oxygen are produced, what mass of H2O2 decomposed?  a. 72 grams  b. 136 grams  c. 64 grams  d. Not enough information given Law of Conservation of Mass

 Heterogeneous mixture  Individual components are often easily separated Mixtures

 Also known as solutions.  Individual components are non-identifiable.  Solvents do the dissolving  Solutes are what get dissolved. Homogenous mixtures

 Filtration  Distillation  Crystallization  Chromatography Separating mixtures

 Pure substances not separated into anything simpler.  91 naturally occurring elements  Rules for writing symbols  1 st letter is capitalized  The Periodic Table…a quick look… Elements

 A combination of 2+ different elements that are chemically combined Compounds

 Individual compounds are composed of the same elements and proportion by mass.  Glucose (C 6 H 12 O 6 )  C = 42.2%  H = 6.5%  O = 51.3% Law of Definite Proportions

Question: What does the law of multiple proportions mean? Answer: Let's see an example: Hydrogen can react with oxygen in a couple of different ways. One way occurs when you take two moles of hydrogen and react it with one mole of oxygen. When you do this, you make H 2 O. Another way occurs when you take one mole of hydrogen and react it with one mole of oxygen: When you do this, you make H 2 O 2. In the first case, two moles of hydrogen weigh 4 grams and one mole of oxygen weighs 32 grams. The ratio of oxygen to hydrogen is 8:1. In the second case, one mole of hydrogen weighs 2 grams and one mole of oxygen weighs 32 grams. The ratio of oxygen to hydrogen is 16:1. Since 16 is equal to 8 x 2, this satisfies the law of multiple proportions. What you'll find is that any time two elements can form more than one compound with each other, this kind of relationship between the masses takes place. Law of Multiple Proportions