When the microwave dings, what comes out hot?
Beep, beep, beep… the microwave is starting! A bowl of soup and a flat little plate go inside, side by side. The microwave fills its box with something you can't even see. In one whole minute it will go… ding! One of them might come out hot. So let's guess first, before we peek… when it dings, what do you think is hot — the soup, or the plate?
After you watchWhen the microwave dings, what comes out hot?
The short answer
When the microwave dings, the soup comes out hot and the plate stays cool. A microwave heats by shaking tiny bits of water, and soup is full of water while a dry plate has almost none.
Try this next
- What if you put in a wet sponge next to the dry plate? Picture the wet thing and the dry thing in the microwave. Guess which one gets hot first, then imagine which one fills up with wiggling water.
- What if the bowl was empty with nothing in it? Guess whether an empty bowl gets hot like the soup did. Think about whether there's any water inside for the microwave to shake.
The whole story
How it works
A microwave fills its box with an invisible wave that shakes water. Food like soup is packed with water, so it shakes and gets hot fast. A dry plate has almost no water inside, so the wave slips right through it and it barely warms up on its own.
What people get wrong
Little kids often think a microwave heats everything inside the same way, like a hot oven warming the whole room. It doesn't — it mostly shakes water. That's why the soup steams but the plate can still feel cool when it dings.
The catch
Shaking the water is fast, but the plate being cool isn't a promise. The hot soup touches the plate and warms its edge, so a plate can still feel warm and can warm your fingers — always check before you grab.
Questions kids ask
Why does the soup get hot but not the plate?
A microwave shakes tiny bits of water to make heat. Soup is full of water, so it shakes and gets hot. A dry plate has almost no water, so it stays cool.
Why is the plate a little warm when I take the soup out?
The hot soup is touching the plate, so it warms the plate's edge, just like a warm cup warms your hands. The microwave didn't heat the plate — the soup did.
Does a microwave heat everything inside it?
No. It mostly shakes water. Wet, watery things get hot fast. Very dry things barely warm up at all on their own.
Talk about it
- Before it dings, let's guess together: will the soup or the plate be hotter? Why do you think so?
- The soup is steaming but the plate feels cool — what do you think is different about them?
- Where do you think the water is hiding inside our food?
Keep going
What else makes you wonder?
- If a microwave shakes water, what happens to something with no water at all, like a dry cracker?
- Why does the plate feel a little warm when you take the soup out?
- What other warm things in the kitchen are full of water?