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Learning about evaporation and how heat turns water into invisible steam.
Have you ever noticed that a puddle on the sidewalk disappears after the sun comes out? It didn't sink into the ground and no one soaked it up with a sponge—so where did it go?
Everything around us is made of matter. Water is a liquid, which means it flows and fills the shape of a cup. But water has a secret! When it gets warm, it can turn into a gas. This process is called evaporation. When water evaporates, it turns into tiny pieces that are too small for our eyes to see. These tiny pieces float up into the air and become something called water vapor. Even though you can't see it, the water is still there—it's just hiding in the air as a gas!
Think about what happens after you wash your hands: 1. Your hands are wet with liquid water. 2. You wave them around in the air or stand under a warm hand dryer. 3. The warmth and the air make the water turn into invisible gas. 4. Your hands become dry because the water has moved into the air!
Quick Check
What is the name of the process where liquid water turns into a gas?
Answer
Evaporation
Why do puddles disappear faster on a hot, sunny day than on a cold, cloudy one? It's because of heat energy. Imagine the tiny bits of water in a puddle are like little dancers. When the sun shines on them, it gives them energy to dance faster and faster. Eventually, they dance so fast that they 'jump' right out of the puddle and into the air! The hotter the water gets, the faster it turns into gas. This is why a puddle in the sun might vanish in one hour, while a puddle in the shade stays all day.
Imagine two puddles of the same size: 1. Puddle A is in the bright, hot sun (F). 2. Puddle B is under a big, leafy tree in the shade (F). 3. Puddle A will disappear first because the sun provides more heat energy to speed up evaporation.
Quick Check
Where does the water go when a puddle dries up?
Answer
It turns into an invisible gas (water vapor) and goes into the air.
When we heat water on a stove, we see something very cool happen. As the water gets very hot, it starts to bubble. This is the liquid turning into gas very quickly! The hot gas that rises from boiling water is called steam. You might see a white mist above a pot of soup; that mist is actually tiny drops of water catching a ride on the hot steam. Steam is a very powerful gas that carries a lot of heat. It is just another way that water changes from a liquid to a gas when we add heat.
If an adult leaves a pot of water boiling on the stove for a long time: 1. The heat stays very high. 2. The water turns into steam constantly. 3. If they wait long enough, the pot will eventually be empty! 4. All the liquid water has turned into gas and moved into the kitchen air.
What is water called when it is in its gas form in the air?
Which of these makes water evaporate the fastest?
Steam is a gas formed by heating water.
Review Tomorrow
Tomorrow, look for a wet spot on the ground or a wet towel. Try to explain to someone where that water will go when it dries.
Practice Activity
With an adult's help, put a small cup of water on a sunny windowsill. Mark the water level with a piece of tape. Check it every day to see the water 'disappear' through evaporation!