Expand and Contract
Science Concepts—Expand and Contract
Summary: As the ocean’s temperature increases, its volume expands. In this activity, students heat and measure volume of air in a balloon to demonstrate the concept that heat causes most substances to expand and become less dense. Then they observe a demonstration that shows that liquid water (above 4 degrees C) also expands when heated.
Concepts to teach:
- Crosscutting Concepts
- Energy and Matter
- Disciplinary Core Ideas
- PS1.A – Structure and Properties of Matter
- PS3.B – Conservation of Energy and Energy Transfer
- Science Practices
- Planning and carrying out investigations, Developing and using models
Goals:
- When most materials are heated (including water above 4 degrees C ) the volume increases due to a process called thermal expansion.
- Thermal expansion is the primary cause of climate induced sea level rise.
- A model can demonstrate a scientific concept.
Standards: NGSS Performance Expectations
- 4-PS3-2.Make observations to provide evidence that energy can be transferred from place to place by sound, light, heat, and electric currents.
- 5-PS1-1. Develop a model to describe that matter is made of particles too small to be seen.
Specific Objectives:
Students will be able to:
- Understand that heat causes most substances to expand and become less dense
- Set up a simple data table to record results
- Observe that heated water has more volume than cooler water
- Explain how sea level rise results in part from thermal expansion
Activity Links and Resources:
- Activity: Size-changing Science: How gases expand and contract from Science Buddies at Scientific American
- Students measure the volume of air in a balloon before and after the air has been cooled or heated, and relate the results to the kinetic energy of molecules.
- Check for potential misconceptions: Ask students to draw a picture of what is going on inside the balloon. That is, a closed balloon has the same number of molecules inside it although the temperature and volume of the balloon changes. Example
- Demonstration: COSEE’s Thermal Expansion and Sea Level Rise – This experiment demonstrates the relationship between water volume and water temperature.
- Set up this experiment as a demonstration to illustrate that water also expands when heated. Train a flex camera on the ruler and project the image on the screen for the entire class to follow and collect data.
- Discuss with students what effect an increase in ocean temperature will have on its volume. If ocean volume increases, where will the ‘extra’ water go?
Assessment:
- In the experiments, what happened to the balloon volume as the temperature changed?
- Have students draw pictures of the balloons in the experiments to demonstrate their understanding of density and volume.
- In the demonstration with liquid water, what happened to the water level when it was heated?
- What happens to the volume of the Earth’s ocean when the temperature of the water increases? How does this affect sea level?
