How Things Work 3-minute video · ages 4-8 · free coloring page
Why does the bathroom mirror get foggy after a shower?
I take a nice hot shower. When I step out, the mirror is all foggy, and I cannot see my face! Why does the bathroom mirror get foggy?
3 min
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Free coloring page
The scene from the video as a coloring page, plus the three-sentence answer, the experiment, and a QR code back to this page. One sheet, US Letter, black and white.
The answer in three parts
Why?
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Hot water sends tiny water bits into the air.
Water is made of teeny tiny water bits, and they are always wiggling. When water is hot, some bits wiggle so fast that they fly off into the air, as a gas you cannot see. It is called water vapor. A hot shower fills the whole bathroom with them.
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On the cool glass, the water bits slow down and stick.
The mirror is much cooler than the warm, wet air. When the flying water bits bump into it, they lose their heat and slow down, so they cannot fly anymore. They huddle together and turn into thousands of tiny drops.
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Tiny drops make a white blur.
Each little drop bends the light in a different direction. So the mirror cannot show a clear picture anymore. That is the fog!
For grown-ups: When water in the air turns back into drops, it is called condensation. It is just the opposite of sweat drying on your skin.
Where else can you find it?
- A cold glass of lemonadedrops on the outside
- Grass in the morningdew
- Your breath on a cold winter daya little cloud of tiny drops
A tiny experiment
Try it!
Breathe on a mirror
You need: a small mirror or a spoon
- Hold a small mirror or a spoon close to your mouth, and breathe out slowly. Haaa! It gets foggy.
- Now watch closely. How fast does the fog go away?
- Then draw a smiley face in the fog on the bathroom mirror!
What happened? Your warm breath has water bits in it. On the cool glass they turn back into tiny drops, just like after a shower.
Did you know?
How does the mirror get clear again? Open the door or a window, and drier air comes in. The tiny drops warm up, fly off again, and the fog fades away.
Your guide in this video
It's me, Droppy, the little water drop. Today we will solve a steamy bathroom mystery!
Droppy is a little blue water drop. Droppy also shows you how sweat keeps you cool.
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