1. CHEMISTRY: ATOMS, ELEMENTS, AND COMPOUNDS Physical & Chemical Changes Combustion Corrosion

2. Changes in Matter Physical Changes No new substance is formed New properties are temporary Change can be reversed There is only a change in form or shape examples  Ice melting  Water freezing  Chopping wood  Tearing paper

3. Changes of State: a physical change

4. Changes in Matter Chemical Changes New substance is formed New properties Cannot reverse the change Examples:  Wood burning (combustion)  Iron rusting (corrosion)  Baking soda reacting with vinegar to produce bubbles

5. Chemical Changes Evidence of a chemical change: Colour change Heat is absorbed or released Gas bubbles form in a liquid A new solid (precipitate) forms Light is released A new odour is produced A sound is produced

6. Homework Read pg. 28 – 30 Answer # 1 – 4 on pg. 30

7. Corrosion: a chemical change a metal loses its properties because of a chemical change with its environment it is a very slow process corrosion looks different for different types of metals

8. Corrosion of Iron: Rusting iron reacts with oxygen to form iron oxide (rust) the oxygen can come from air or water

9. Preventing Corrosion prevention is based on stopping the metal from being exposed to oxygen avoid exposure to air or water 1. paint the surface of the metal 2. spray the bottom and inner surfaces with oil 3. coat with other metals

10. Homework Read pg. 34 – 35 Answer # 1 – 3, 5 – 7 on pg. 35

11. Combustion: a chemical change When a substance reacts with oxygen in the air to produce CO 2, H 2 O, and energy Complete combustion CH 4 + 2O 2 → CO 2 + 2H 2 O + energy (reactants) (products) CH 4 is a fuel (hydrocarbon) which only contains carbon and hydrogen all reactants are used up to produce products

12. Combustion: a chemical change Incomplete combustion CH 4 + 2O 2 → CO 2 + 2H 2 O + energy + CO + other pollutants Not all the reactants mix and it produces other products harmful to the environment ex: exhaust coming out of a car

13. Homework Read pg. 38 – 39 Answer # 1 – 5, 7 on pg. 39