Why do some things float and other things

Why do some things float and other things sink?

1. Let’s think back! • Can you explain why some others sink? • What evidence can you use your ideas? things float and to support • Do you have any evidence that is against your ideas? • Do you agree with other groups’ ideas? What evidence can you think of to challenge them?

2. Making salty water • What happens to the volume of the water when we dissolve salt in it? • What happens to the weight of the water when the salt is added? • What can you say about how heavy for its size salty water is compared to fresh water? • How do you think the salt changes whether things will float or sink in the water?

3. Exploring salty water • What difference do you notice when the water is salty? • How can you explain this difference? What evidence can you use to support what you think? • Do your ideas and rules for fresh water work for salty water? • What is your group’s best explanation so far for why some things float and other things sink?

4. Plenary: eggstraordinary behaviour • What are your ideas about floats in the • What do you know about water and in why the egg middle of the liquid? eggs in fresh salty water? • What is your best explanation for why the egg floats in the middle? • Is there anything you would like to know that would help you decide?