Thermos and insulation test
Wrap identical cans of hot water in cloth, paper, husk or sawdust and compare how fast they cool.
The big idea
Keeping heat in saves energy. This test shows which local materials do it best, using things you may already have.
You will need
Tick things off as you gather them.
Step by step
-
Step 1: Prepare the wrapping
Wrap each can in a different material: cloth, newspaper, and one packed with husk, one with sawdust. Leave one can bare. Wrap each layer the same thickness.
-
Step 2: Fill with hot water
With an adult, fill every can with the same amount of hot water from the same source. Use a lid or card on top of each.
-
Step 3: Record the start
Measure the temperature in each can and write it down. They should all start about the same.
-
Step 4: Measure every 10 minutes
Every 10 minutes for an hour, measure and record the temperature in each can. Use the same thermometer, kept clean.
-
Step 5: Plot a cooling graph
Plot time along the bottom and temperature up the side, one line per can. Compare how steeply each line falls.
-
Step 6: Rank the materials
Which material kept the water warm for longest? Which was the worst? Why might that be?
What to look for
- The bare can cools fastest.
- Dry, fluffy materials, such as husk and sawdust, usually keep heat in best.
- Thicker layers insulate better.
An example of the pattern you should see, not measured data. Your numbers will differ, and that is fine.
Why it works
Heat always moves from hot to cold. A material that is full of tiny pockets of trapped air slows that movement a lot, because still air is a poor conductor. Husk, sawdust and cloth all trap air. A flask works the same way, with a near-empty gap around the inside. Better insulation means less energy is needed to keep a house cool or a fridge cold.
Try this next
- Try two layers of one material and compare with one.
- Test the same wrappings on a can of cold water in the Sun.
- Think about how insulation could help in your own house or school.
Stay safe
Hot water can scald. Ask an adult to pour. Do not use boiling water.
Link to the grid
Better insulation is the cheapest way to cut electricity use. A well-insulated home needs less fan, cooler and air-conditioning power.
Learn how the grid works