Students warm butter until it melts and then cool it until it turns hard again as they investigate the question: How do substances change when they are warmed and cooled?
Objective
Students will be able to explain that cooling water can change it to ice and that heating ice can change it back to liquid water. Students will be able to explain that this process can also happen to other substances. Students will also be able to explain that heating a substance makes its molecules move faster and cooling a substance makes its molecules move slower. The lesson can also be used to lay a foundation for learning about changes in state and chemical changes which can be further developed in later grades.
Key Concepts
- If water is cooled enough it can change to ice.
- If ice is warmed enough, it can change to liquid water.
- Heating a substance makes the molecules move faster.
- Cooling a substance makes the molecules move slower.
NGSS Alignment
- NGSS 2-PS1-4:Â Construct an argument with evidence that some changes caused by heating and cooling can be reversed and some cannot.
Summary
- Students see a video of water freezing and then melting.
- Students warm butter until it melts and then cool it until it turns hard again.
- Students view an animation showing that heat causes the molecules in butter to move faster and separate from each other. They also see that cooling butter makes the molecules move more slowly and come back together.
- Students participate in a class discussion about how heating and cooling can cause changes in matter.
Evaluation
Download the Student Activity Sheet (PDF) and distribute one per student when specified in the activity. The activity sheet will serve as the Evaluate component of the 5-E lesson plan.