Book 1, Question 140 · Video
Why Does Water Boil at 100°C? Molecules Break Free!
Heat makes water molecules fly apart. At 100 degrees C they have enough energy to become steam. The page says high mountains boil a bit cooler because air presses less, and salt wa
Read the full answer →What Crafty Clover says in this video
Intro
Hi! I'm Crafty Clover! Let's discover something amazing. Today's question is, why does water boil at one hundred degrees Celsius?
The Big Idea
Heat a pot of water, and soon it bubbles and steams. That's boiling! Here's a secret: the Celsius scale was made using water. Zero for freezing, one hundred for boiling! But what's really happening in the pot?
Molecules Spread Out
Step one: heat makes water molecules pull away from each other. Water is made of tiny molecules that hold hands, sticking together. As water heats up, they jiggle faster and faster, until they can pull free and fly away.
Steam
Step two: at 100°C, they have enough energy to become steam. At sea level, molecules all through the water can now escape as a gas, called steam. The bubbles are pockets of steam!
Mountains
Step three: high mountains boil a bit cooler, because air presses down less. Way up high, there's less air pushing on the water. So molecules escape more easily, and water boils at around seventy degrees on the top of Mount Everest!
A Closer Look
Let's look inside a boiling pot! At the top, steam escapes into the air. Inside, bubbles of steam rise up through the water. And the stove keeps adding heat, to keep it boiling.
Quick Facts
Quick facts! Salt water boils a little hotter, but a pinch of salt only changes it a tiny bit. Real steam is invisible! The white cloud is tiny water droplets. On Mount Everest, water boils at only about seventy degrees Celsius. In Fahrenheit, water boils at two hundred and twelve degrees.
Think Like a Scientist
Now, think like a scientist! With a grown-up, watch a pot of water heat up on the stove. First you'll see tiny bubbles, then big rolling bubbles, and steam rising. But remember: never lean over the pot. Steam is very hot!
Outro
So water boils at one hundred degrees Celsius because that's when its molecules have enough energy to escape as steam! Crafty Clover can be found on Amazon Books, Google Bookstore, and Apple Books. Available for purchase or download! Bye for now!