Temperatures are rising, and your students are eager to play outdoors. But spending too much time in the heat puts them at risk for dehydration. This science experiment is designed to demonstrate the effects of dehydration and teach students the importance of staying hydrated in hot weather.

What is dehydration?

Before starting the experiment, explain dehydration and its effects on the body.

Your body is about 60-70% water, and it needs a certain amount of water to function properly. But when it’s hot and you’re playing hard, you perspire (or sweat), which helps to regulate your body temperature by cooling you down. If you don’t hydrate, or replace the water that you lose through perspiration, you’ll become dehydrated. Dehydration can make you feel sick or, in worst cases, cost you a trip to the hospital.

How can you tell if you’re dehydrated?

Being thirsty is the first sign. Dehydration can also cause dizziness, lightheadedness, fatigue, rapid heartbeat and dry lips and mouth.

Dehydrated Potato

This activity has been adapted from Science Fair Adventure.


  • 1 potato (small or medium size)
  • 2 dishes or saucers (deep enough to hold about a half-inch of water)
  • Cutting board
  • Knife
  • Salt (about 2 tablespoons)
  • Water
  • Piece of paper
  • Pen, pencil, or marker
  • Adult supervision


  1. Take your paper and label it with the word "salted" and place it on a table or other flat surface.
  2. Place one dish on the paper and the other dish next to it on the table.
  3. Fill each dish with an equal amount of water (the water level should be high enough to fill the dish, but not so high that it overflows).
  4. Stir two tablespoons of salt into the dish marked "salted'.
  5. Using your knife and cutting board, cut the potato in half to make two equal size pieces. (This step should be completed by an adult)
  6. Place one-half of the potato, flat side down, into the dish marked "salted".
  7. Place the other half of the potato, flat side down, into the dish with plain water.
  8. Let the potatoes sit in the dishes undisturbed for about an hour. Once the hour is up, allow students to observe the results.

Science Behind the Experiment:

After an hour, students will observe a notable difference in the potato halves. The potato in plain water will be mostly unchanged. But the potato in salt water will be shriveled. The salt water acts as a dehydrator by drawing moisture out of the potato. As the water is drawn out of the potato, the potato begins to get dehydrated and causes it to shrivel.

Similarly, there are several dehydrators - like sweat - that draw water from our bodies. Losing too much water without replenishing it can affect major organs like the heart, lungs, kidneys and intestines. The key is to make sure students stay hydrated by drinking at least eight cups of water per day or more if they’re spending time outside in the heat.

For more heat safety activities, check out this sunscreen experiment. For tips on protecting students’ skin from the sun, read Summer Safety: How To Protect Children’s Skin From The Sun.