1. Physical and Chemical Changes

2. Think of all the words you can to describe physical changes and come and write them on the board.

3. What about dissolving?

4. Think of all the chemical changes you can think of and come and write them on the board.

5. Chemical Change Something new is produced.
The “old” materials are called REACTANTS
The “new” materials are called the PRODUCTS
Chemical Change

6. Evidence for Chemical Changes
Colour Change
Heat, light, or sound produced
Heat, light, or sound consumed
Bubbles of gas form
A precipitate may form
Evidence for Chemical Changes

7. Physical and Chemical Changes
Often, physical and chemical changes happen at the same time
When you use an explosive to blast rock, gas is produced
There is obvious physical changes though too
Physical and Chemical Changes

8. Exothermic Reaction All reactions involve changes in energy!
An exothermic reaction RELASES energy in the form of heat or light
For example, in a battery, electricity is produced by exothermic chemical reactions…you can feel the heat of a battery!
Exothermic Reaction

9. Enodthermic Reaction All reactions involve changes in energy!
An endothermic reaction absorbs energy from the system
For example, when you recharge a battery, electrical energy is absorbed by the chemicals in the battery.
Enodthermic Reaction

10. Corrosion Corrosion is a chemical reaction
Corrosion involves the breakdown of metals
Rust occurs when iron mixes with the oxygen in water.
Can you think of any examples when corrosion is good?
Corrosion