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Which coat keeps an ice cube from melting?

Some materials slow heat down. They are called insulators. Wrap ice cubes in different “coats,” race them, and find the best one. Your house wears a coat like this in the attic.

Goldstrike, your Wing Force guide
Goldstrike says“Which coat wins? Ready, set, melt!”

⏱ About 30-60 minutes (mostly waiting). 💧 Melty, so use plates. Grown-up helps: timing and checking.


2 pages: the experiment, then a page to write your results.

What you need

  • 5 ice cubes, all the same size (from the same tray is best)
  • 5 small plates or plastic cups
  • Wraps to test, such as:
    • nothing at all (this one is your “no coat” cube)
    • aluminum foil
    • a paper napkin
    • a wool or thick cotton sock
    • bubble wrap, or a cotton ball pile
  • A clock or timer
  • Paper and a pencil for your chart

Make a guess

Which ice cube do you think will melt last? Which will melt first? Pick your guess before you start.

Tap your guess: Which wrap will keep the ice cube frozen longest?

Steps

  1. Label each plate with the name of its wrap.
  2. Working fast, wrap one ice cube in each material. Leave one cube with no wrap. Wrap each one about the same, all the way around.
  3. Set all the plates side by side in the same spot, out of the sun.
  4. Write down the start time. That is your 0 minute check.
  5. Every 10 minutes, peek at each cube. Open the wrap just a little, then close it again fast. Write down how big each cube looks.
  6. When the “no coat” cube is all melted, check all the others and write what you see.
  7. Keep going until each cube melts, if you can. Which one lasted longest?

My melt chart

WrapMy guess (1st to melt = 1)0 min10 min20 min30 min40 minMelted at
No coat
Foil
Napkin
Sock
Bubble wrap or cotton

What you will see

The cube with no coat melts first. Fluffy, puffy wraps like a wool sock, bubble wrap or cotton balls usually keep ice frozen the longest. Many people are surprised that a “warm” sock keeps ice cold! Shiny foil wrapped tight on the cube often does not help much on its own.

Your results might be a little different. That is fine. Scientists write down what really happened.

Why it works

Heat always moves from warmer things to colder things. The warm room is always trying to push heat into the cold ice cube. That heat makes it melt.

Some materials let heat pass through quickly. They are called conductors (con-DUCK-ters). Metal, like foil, is a good conductor. Other materials slow heat down a lot. They are called insulators (IN-suh-lay-ters).

The best insulators are full of tiny pockets of trapped air. Air that is trapped and can’t move around is very slow at moving heat. A sock, bubble wrap and cotton are full of little air pockets, so they slow the heat on its way to the ice. A sock does not make heat. It just slows heat down, so it keeps warm things warm and cold things cold!

How your house uses this

On a summer day in Austin, the sun bakes the roof, and the attic gets much hotter than the rooms below. That heat tries to move down into your house, just like room heat moving into the ice cube.

  • Most attics have a thick, fluffy layer on the floor called insulation. It is full of trapped air pockets, like your sock or cotton.
  • Insulation slows the attic heat from getting into your rooms in summer. In winter, it slows the warm air in your rooms from escaping up.
  • Your AC ducts often run through the attic. They are wrapped in insulation too, so the cool air stays cool on its way to your rooms. It is like a coat for the air.
  • Thick walls, closed windows and closed doors help in the same way.

Think of insulation as your house’s coat. It does not make cold or heat. It just helps your house keep what it has.

Leave the attic and its itchy insulation to the grown-ups.

Try this next

  • Thick vs thin. Wrap one cube in one napkin and another in five napkins. Does a thicker coat work better?
  • Tight vs fluffy. Wrap one cube in a squished cotton ball and one in a fluffy cotton ball. Which lasts longer? Why do you think so?
  • Keep it warm. Flip the race around. A grown-up fills small cups with warm tap water. Wrap each cup in a different coat and feel which stays warm longest.
  • Sunny spot vs shady spot. Put one unwrapped cube in a sunny window and one in the shade. How much faster does the sunny one melt? This is why Shade Squad closes blinds on the sunny side.
  • Lunchbox test. Does an ice pack last longer in an insulated lunchbox or a paper bag?

Share what you found

Show your grown-up your chart. Ask them which coat they would have picked, then show them the winner.


2 pages: the experiment, then a page to write your results.

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