Do Try This At Home: Make dew and frost

Published: Aug. 23, 2021 at 1:00 PM CDT
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AMARILLO, Texas (KFDA) - For this week’s Do Try It At Home with the Don Harrington Discovery Center, we are making dew and frost.

For the experiment, you will need the following materials:

  • 2 empty tin cans with no lid (peel the labels off)
  • Rock salt or table salt
  • Crushed ice
  • Water

Here is the procedure:

  • Fill both cans halfway with the crushed ice.
  • Add four tablespoons of salt to one of the cans and let sit for about 30 seconds.
  • Add just enough water to the other can to just cover the ice.
  • Frost will form on the outside of the can with ice & salt and dew will form on the can with ice & water.

Below is an explanation of the experiment:

  • What is happening? The difference is the reaction between the salt and the ice. The salt wants to absorb the ice and create a salt solution. To do this, the ice has to melt. How can this ice melt? The heat actually comes from inside the ice itself. The reaction actually makes the mixture cooler! So much cooler that it goes past its dew point and below freezing. This causes any water vapor in the air that collects on the outside of the can to freeze and make frost. The dew point is the temperature that causes water vapor to turn into liquid. When the temperature is cold enough to freeze that liquid, we get frost!
  • In the other can, the ice that is below freezing causes the water vapor in the air around the can to reach its dew point and create the water droplets on the can. But it is not cold enough to freeze and create frost. This is a process called condensation and is also an important part of the water cycle.
  • You’ve seen water in many forms: rain, sleet, snow, frost, dew, and more! Water behaves differently depending on the temperature and atmosphere around it. Water freezes at around a temperature of 30 degrees fahrenheit and the atmosphere around the water in the air is what produces things like snow, sleet, hail, and frost!

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