## What is the best insulation?

By Marshall Brain

Insulation keeps hot stuff hot and cold stuff cold. A blanket is a good example of an insulator - a blanket keeps you warm at night. In the video we tried several different types of insulation (including paper towels, newspaper and aluminum foil) to see which one would do the best job of keeping heat in. You can try anything you like.

In the video we came up with a hypothesis about which insulator we thought would do best. A hypothesis is just an educated guess about what we think will happen when we run the experiment. In the video, we guessed that paper towels would be the best insulator because they are the thickest, fluffiest insulator we tried.

To test different types of insulation, here is what you need:

• Some foam cups
• Different types of insulation cut in circles so they cover the top of the cup
• Hot water from the tap
• A container to hold the hot water so you can pour it in the cups
• Thermometer
Set up your foam cups and pour the same amount of hot water in each of them. Do not fill them to the brim -- we do not want to get our insulation wet. Leave maybe an inch of air space. You may want to double up or triple the foam cups (we doubled them in the video - this provides more insulation on the sides of the cup).

Measure the starting temperature in the cups. It will take about 30 seconds for the thermometer to settle on the right temperature as you move from cup to cup. The starting temperature should be the same in all cups.

Now cover the cups with the different types of insulation you are testing. Every 10 or 15 minutes (you can choose any time interval you like for your experiment), measure and record the temperature in each cup. To do this, you will want to lift off the insulation, stick the thermometer in the water for 30 seconds to get an accurate reading, immediately put the insulation back on and then record the temperature. Try to keep the insulating cover off the cup for the shortest amount of time possible. In the video, our procedure was to remove the cover, stir the water vigorously to get the temperature uniform throughout the cup, measure the temperature at the top of the water (could have just as easily been the bottom) for 30 seconds, and then immediately replace the insulating cover.

You can try all kinds of different types of insulation at home. Try plastic wrap, foam, bubble wrap, dried leaves, insulation from the attic... anything really. You can test different thicknesses. You could try cold water instead of hot water, or hot pieces of metal (make sure they are identical) instead of hot water. Try anything! Have fun performing your own science experiments!

Bonus question: Why did aluminum foil work better than paper towels alone? What is it about aluminum foil that helps it keep heat in? Do some research and see what you can find. Hint: There are three ways that heat dissipates: radiation, conduction and convection. Your research may help you think of other types of insulation that will work well.