Ever leave a cup with water in it and after a few days notice the liquid slowly disappear? It didn’t boil, but it did something else. This month, we’ll be learning about one of Nature’s processes: evaporation. Most kids learn this as a part of the rain cycle but evaporation happens all the time and with things other than water! Let’s learn about this process with a few simple experiments, and hopefully, you’ll be on your way to asking questions and wanting to learn more.
Materials:
Liquid hand sanitizer. That’s it!
Procedure:
- Put a little squirt of hand sanitizer on the palm of your hand (about the size of a penny)
- Let it sit there for a minute. Notice what is happening to it
- Blow on your hand or fan it with a piece of paper
Explanation:
Did you notice what happened to the liquid hand sanitizer when you put it on your hand? It started to “melt” and spread out on your palm. You should have started to notice the puddle start to shrink, too, after a minute and if you had enough patience, it “disappeared!” Another startling thing you should also have noticed was how it felt on your hand: It felt cold!
Not because the liquid was cold, but because of what was happening to it. Can you guess? Liquids such as water and hand sanitizer at room temperature can turn into a gas (also called a vapor in this instance) through a process called evaporation. And what does this process need? Energy! And in this case, the energy is your own hand’s heat. That’s why it “felt” cold; it was stealing your heat to do this task. So feeling the cold, was feeling the hand sanitizer taking your heat in order to turn into a gas!
Going further:
Maybe you can answer this question: “Why do people sweat?” Think about it! It has everything to do with what you just learned with the sanitizer.
Yes, people sweat when they do some exercise because they’re hot. The sweat itself doesn’t cool you down; think about what will happen to the liquid sweat. It will evaporate! And in order to evaporate it steals your body’s heat and will cool you down. So make sure you drink plenty of water!
Pro tip: One summer a long time ago I worked for a roofing company. It was hot! One tip some of the guys told me was to not just drink water, but to dab some cool water on my wrists and also the sides of my neck. These are spots with high blood flow and when the water evaporates there, your body can really feel the cold quicker!
Maybe you can do some more experiments on your own. Which types of liquids evaporate the fastest? Put some drops of liquids on a plate under a fan and see which ones “disappear” first.
Keep track of what you learned here today in a journal: you never know when you might ask a good science question, or need to apply what you’ve learned in an experiment.
LOOKING FOR MORE science experiments? Find them here!
About the author:
Steve Davala has been teaching math and science to middle and high schoolers since 2000. He writes books, plays music, carves wood and he loves learning new things. Ask him a question at steve.davala@gmail.com.
