Hot and cold
Why does a cup of cocoa cool down and an ice lolly melt? Heat moves from hot things to cold things. Find out what keeps things warm, and test which wrap keeps warm water warm the longest.
Read
Some things are hot, like soup. Some things are cold, like ice. A thermometer tells us how hot or cold something is.[1]
Heat always moves from a hotter thing to a colder thing. That is why a hot drink cools down and an ice cube in your hand melts.[5][2]
Heat moves easily through metal. Put a metal spoon in hot soup, and soon the handle is hot too! Wood lets heat through much more slowly.[3][4]
Air lets heat through only slowly. Trapped air keeps things warm. Penguins trap air in their feathers, and a cat fluffs up its fur.[3][5]
Things that slow heat down are called insulators. Layers of clothes and foam cups are insulators.[5]
The Sun warms the ground. You can feel the warmth of a campfire on your face, even without touching it.[3]
Try it: Keep it warm!
You need
- 3 or 4 small jars or plastic cups, all the same
- Warm water from the tap (the teacher fills the cups)
- Wraps: a scarf or sock, bubble wrap, kitchen foil, nothing
- Elastic bands
- A thermometer (or just your finger)
Safety
Use warm water from the tap only, never hot or boiling water. The teacher pours. Mop up spills straight away.
What to do
- Wrap each cup in a different material. Leave one cup with no wrap.
- The teacher pours the same amount of warm water into every cup.
- Guess which cup will stay warm the longest.
- Wait 20 minutes. Then feel each cup's water with a finger, or measure it with the thermometer.
- Put the cups in order from warmest to coolest. Was your guess right?
Play: Keeps warm or lets heat through?
Does it slow heat down (keeps warm) or let heat through easily? Tap the right group.
Your best score is kept only on this device. Nothing is sent anywhere.
Quiz
Other ages: Ages 10–11 · Ages 15–16