CHEMISTRY: ATOMS, ELEMENTS, AND COMPOUNDS

Physical & Chemical Changes

Combustion

Corrosion

Changes in MatterPhysical 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

Changes of State: a physical change

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

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

Homework

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

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

Corrosion of Iron: Rusting

iron reacts with oxygen to form iron oxide (rust)

the oxygen can come from air or water

Preventing Corrosion

prevention is based on stopping the metal from being exposed to oxygen

avoid exposure to air or water1. paint the surface of the metal

2. spray the bottom and inner surfaces with oil

3. coat with other metals

Homework

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

Combustion: a chemical change

Combustion: a chemical change

Homework

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