The Power of the Sun

• The heat of the sun varies from place to place, and with it, rates of evaporation.Comstock/Comstock/Getty Images
  
  You can use the power of the sun to help kids learn about evaporation. On a warm day, take two identical clear jars or glasses and fill them with exactly the same amount of water using a measuring cup. Use a piece of masking tape to mark where the water line is on each. Ask your child to find a nice sunny spot for one and a shady spot for another. Let the jars sit for the rest of the day and check on them every hour or so. The kids should predict the results before the experiment and explain what they think affects the evaporation rates.
  
  

Water Temperature

• Exposure to the sun is not the only factor affecting evaporation. Temperature matters too. Take two equal amounts of water in identical glasses and mark the waterline with tape. This time, put cold water in one and hot water in another and place them both in the sun. Your kids might be able to guess the hot water will evaporate faster, but why? Heat matters, regardless of the source. You can explain that very hot water is already in the process of evaporation when steam is present.
  
  

Chemical Composition

• Adding salt to water changes its chemical composition and its evaporation rate.Hemera Technologies/AbleStock.com/Getty Images
  
  Would color matter? What about salt? You can try the same basic experiment by adding color to one glass of water, or different colors to see if it matters. You can mix up a glass of salt water using several tablespoons of salt and the kids can predict and observe the differences in water evaporation. This experiment will also demonstrate that the salt does not evaporate with the water.
  
  

Variations

• As ice melts it turns to a liquid first, but then evaporates.Jupiterimages/liquidlibrary/Getty Images
  
  There are a number of other fluids that will evaporate, so you could try different substances. For example, soda, juice, or rubbing alcohol all have chemical properties that differ from water. Heavier fluids, like soda, will generally evaporate slower, but alcohol will turn into a gas much more quickly. You can also have kids time the evaporation as though it was a race, making predictions based on what they learned. Or, you could try cubes of ice to discuss another property of matter -- solids. The kids can think about how long it will take to turn to a liquid and how long it will take to dry out completely.