How to Create a Density Experiment

Changes in temperature result in changes in density. Playing with this relationship between density and temperature can create a challenging science experience for middle school and high school students. If you plan it properly, you will have enough material to keep you busy for a week in science class.

Difficulty: Moderate

Instructions

Things You'll Need:

• Water
• Beakers
• Cooking oil
• Salt
• Hot plate
• Food coloring
• Ice
• Spoons
• Stirrers
• Hot pads

1. Help students define density. Ask them:
   What is density? What differences in density do you notice in the world around you? In the classroom? Define temperature.
   What is temperature? What differences in temperature do you notice in the world around you? In the classroom?
   How does temperature affect density? If something is heated, what happens to the molecules? Does it become less dense or more dense?
   Try to find as many real-life examples of the temperature-density relationship as you can: this will help students prepare for their lab and their homework assignment.

2. Students will try to create three distinct layers in a glass beaker.
   First with temperature, using:
   *Ice water
   *Room temp water
   *Boiling water
   Then with chemistry, using:
   *salt water
   *tap water
   *cooking oil
   
   It will be easier to SEE separate layers if each one has a different color. You can bend a spoon and have students pour each new layer into the flat part of the spoon to help keep the layers intact. Something like pouring the stout into the ale when making a black & tan.

3. Make a lava lamp.
   Put a three-layered beaker on a hot plate and turn it up to medium high.
   While you are waiting... talk to your students...
   Make a prediction - what do you think will happen to the layers?
   Record your observations - what actually does happen?
   How do you explain the difference between what you thought would happen and what you observed?
   What would you do differently next time?

4. For a long-term project or homework assignment:
   Study Galileo's design for the barometer. Galileo used differences in densities to reflect changes in temperature.
   Ask students to design their own barometer, using household items.
   Ask them:
   What materials would you use?
   What would you put inside your "bubbles"?
   What liquid would your bubbles float best in?
   If you were to make five separate bubbles, what temperature would make each bubble float to the surface?

5. For extra credit...
   Students can actually MAKE their gadget and bring it in to class!

Tips & Warnings

• Encourage students to use their imagination in creating their instrument. You will be amazed what they will come up with.
• Careful with the food coloring in the classroom! Be sure students are wearing lab clothes or smocks. A little bit of dye can do a lot of damage -especially red dye!
• I like to use student helpers, or runners, in my labs. They can help with the details when you are looking at the bigger picture. Offer some kind of incentive for your assistants.
• Protective eye gear should be worn at all times in the science lab, especially when using a heating element.

Resources

• WeatherPatrol.com for weather related equipment
• www.barometers.com for info on weather tools