1. WALT: about chemical and physical change

2. Lesson objective:
To understand the difference between chemical and physical change.
Be able to give examples of chemical and physical changes.
Understand key vocabulary.

3. 1.5 Chemical Change
Chemical change involves the formation of new substances.

4. Different types of chemical reactions
Effervescence
When a gas is formed
Precipitation
When a solid is formed
Colour change
Energy changes
Exothermic
Endothermic

5. Chemical equations Reactants = substances we start with.
Products = the new substances that are formed.
Reactants Products
Example
When we add chalk to an acid;
Calcium carbonate + hydrochloric acid calcium carbonate + water + carbon dioxide

6. Reversing chemical change
Very difficult to reverse a chemical change.
Exception

7. Physical changes No new substances are formed.
In a physical change the substance may change form or may be mixed together.
Physical changes can usually be reversed.

8. Activity
Start to work through the questions on page 19.

9. Plenary
Describe a physical and chemical change to your neighbour.