1. Warm Up Name the two kinds of mixtures List three different separation techniques Is iron rusting a chemical or physical change? If 2g of potassium (K) is reacted with 2g of iodine (I), how much potassium iodide (KI) will you end up with? Today you will need a calculator and a periodic table

2. Matter – Elements & Compounds An element is a pure substance that cannot be separated into simpler substances by chemical or physical means There are over 90 naturally- occurring elements Each has a unique chemical name & symbol

3. Matter – Elements & Compounds The Periodic Table organizes the elements into a grid of:  horizontal rows called PERIODS  vertical columns called GROUPS or FAMILIES

4. Matter – Elements & Compounds Compounds are made up of two or more different elements that are combined chemically H 2 O NaCl C 6 H 12 O 6 CO 2 CaCO 3 NaHCO 3 CH 3 COOH

5. Matter – Elements & Compounds Compounds can be broken down into simpler substances (into elements or into other, smaller compounds) Na + Cl -

6. Law of Definite Proportions A compound is always composed of the same elements in the same proportion by mass Put another way… The mass of the compound is equal to the sum of the masses of the elements mass compound = mass elementA + mass elementB

7. Law of Definite Proportions If the atomic mass of sodium is 23 and the atomic mass of chlorine is 35, what is the mass of the compound NaCl (table salt)? 23 35 + = 58

8. Law of Definite Proportions Percent by mass is the relative amounts of the elements in a compound percent by mass = mass of element mass of compound X 100 It is the ratio of the mass of each element to the total mass of the compound expressed as a percentage

9. Law of Definite Proportions What is the percent by mass of sodium (Na) in table salt? 23 58 X 100= 39.66% What is the percent by mass of oxygen in H 2 0? Atomic mass of hydrogen (H) is 1, atomic mass of oxygen (O) is 16.

10. Law of Multiple Proportions When different compounds are formed by a combination of the same elements, different masses of one element combine with the same fixed mass of the other element in a ratio of small whole numbers.

11. Examples Carbon monoxide (CO) and carbon dioxide (CO 2 ) Water (H 2 O) and hydrogen peroxide (H 2 O 2 )