How the World Works

1. Which of the following is an example of a physical change?

• Burning wood

• Baking a cake

• Melting ice

• Rusting iron

2. What is a sign of a chemical change?

• A change in state

• A new substance is formed

• A change in size

• Dissolving in water

3. Which of these changes can be reversed?

• Freezing water

• Baking bread

• Burning paper

• Cooking an egg

4. What is an example of a harmful chemical change?

• Rusting of metal on bridges

• Melting of ice in hot weather

• Boiling water for cooking

• Stretching a rubber band

5. 5. Which of the following chemical changes has a positive impact on life?

• Corrosion of iron

• Acid rain forming in the atmosphere

• Burning fossil fuels

• Formation of compost from organic waste

6. Why is recycling plastic bottles an example of a physical change?

• The plastic burns and forms new substances

• The shape of the plastic is changed without altering its chemical structure

• The plastic reacts with air to form new materials

7. What property of water changes when it freezes?

• Chemical composition

• Flammability

• Density

• Toxicity

8. What is climate change?

• A change in weather for one day

• A long-term change in the Earth’s temperature and weather patterns

• A holiday about the environment

• A change in the amount of rain for a week

9. Which gas is one of the main causes of global warming?

• Oxygen

• Nitrogen

• Carbon dioxide

• Helium

10.What do greenhouse gases do?

• Make plants grow faster

• Trap heat in the Earth’s atmosphere

• Create more oxygen for us to breathe

• Block sunlight from reaching the Earth