C1.1.2 Chemical And Physical Changes

Question 1

What is a physical change?

Answer 1

A physical change happens when a substance changes state or shape, or breaks into pieces without creating new substances.

Examples include melting butter, freezing juice, and mixing sand with water.

Question 2

List three examples of physical changes.

Answer 2

• Freezing juice to make an ice lolly
• Mixing sand with water
• Dissolving sugar in water

Question 3

What is a chemical change?

Answer 3

A chemical change is a change that produces one or more new substances, which often have different properties than the original substances.

Examples include cooking eggs and steel rusting.

Question 4

List three examples of chemical changes.

Answer 4

• Cooking eggs
• Steel rusting
• An acid reacting with an alkali to make a salt and water

Question 5

What happens to particles during a physical change?

Answer 5

During a physical change, the particles stay the same but their arrangement and movement change.

For example, ice melting into water changes the arrangement of particles from fixed to random.

Question 6

What happens to particles during a chemical change?

Answer 6

In a chemical change, particles break up and then join together in different ways to form new substances.

Question 7

True or False: Many physical changes can be reversed.

Answer 7

True

Question 8

True or False: A chemical change can be easily reversed.

Answer 8

False

Question 9

Fill in the blank: A change that makes new substances is described as a _______.

Answer 9

[chemical change]

Question 10

What should the term ‘chemical’ be used as?

Answer 10

It is best to use the word ‘chemical’ as an adjective to describe something.

For example, ‘chemical change’ or ‘chemical reaction’.

Question 11

Explain why the label ‘chemical-free’ cannot be true for shampoo.

Answer 11

All substances are chemicals, so claiming something is ‘chemical-free’ is misleading.

Question 12

Describe two differences between a chemical change and a physical change.

Answer 12

• Chemical changes produce new substances; physical changes do not
• Chemical changes are often irreversible; physical changes are usually reversible

Question 13

What is the result of mixing flour, sugar, butter, eggs, and baking powder when making cupcakes?

Answer 13

The mixture undergoes both physical and chemical changes when cooked in a hot oven.

Question 14

What is the significance of the particle model in understanding changes?

Answer 14

The particle model helps explain how particles rearrange during physical changes and how they break and form new bonds during chemical changes.