Observations and Physical vs. Chemical Changes

• Science
• Lower Secondary (Key Stage 3)

Observations and Physical vs. Chemical Changes

How can you tell that a chemical reaction has occurred?

Watch each video carefully. What happens in each one that tells you a reaction has happened?

How could you tell a reaction had happened?

What observations did you make?

What observations did you make?

What observations did you make?

What observations did you make?

Is this a chemical reaction?

Yes

No

1. Physical change
2. Chemical change

1. Physical change
2. Chemical change

1. Physical change
2. Chemical change

1. Physical change
2. Chemical change

1. Physical change
2. Chemical change

1. Physical change
2. Chemical change

Are these physical changes or chemical reactions?

Physical change

Chemical reaction

Melting butter

Dissolving salt in water

Burning a bonfire

Freezing water

Adding Mentos to Coca Cola

Baking a cake

An explosion

Give 3 examples of an observation you might make during a reaction.

How do we tell the difference between a physical change and a chemical reaction?

Two colourless liquids mix. They form a yellow solid. Is this a chemical reaction or a physical change. Explain why.