real science for today's homeschooler

Cloud in a Glass

Cloud in a Glass

As you’re studying weather, take a few minutes to make a cloud in a glass to help explain the process of condensation and cloud formation.

What you’ll need: clear glass or jar, kitchen matches, ice cubes, small plate or pan that will completely cover top of glass or jar (metal works best), boiling or very hot water

Procedure:
1. Fill the plate or pan with ice cubes and have it ready to quickly place over the top of the glass when needed.
2. Pour enough boiling water into the glass or jar so that there is about 1/2 centimeter of water covering the bottom.
3. Light a kitchen match and hold it inside the top of the glass for a minute or so. Right before the flame reaches your fingers, drop the match into the water in the glass.
4. Immediately, cover the top of the glass with the pan containing ice cubes.
5. Watch a “cloud” form inside the glass!

What’s Going On?
The boiling water has enough heat energy to cause some of the water molecules to evaporate and turn into water vapor inside the glass. Those individual water molecules will stay in a gas state as long as they have enough energy. When the pan of ice is placed over the top of the glass, heat energy from the water vapor molecules is transferred to the bottom of the cold pan. The water vapor molecules no longer have enough energy to remain in a gas state, and they condense back to a liquid state. The smoke from the burning match is made of tiny particles which remain suspended in the air inside the glass. As the water molecules began to condense, they collect around the smoke particles, forming the tiny water droplets that make the “cloud” in the glass.

How do Real Clouds Form?
Clouds in Earth’s atmosphere form in pretty much the same way. As the Sun’s energy heats water on the surface of the Earth, it evaporates. As the moist air continues to heat up, it begins to rise higher into the atmosphere. Earth’s atmosphere gets colder and colder the higher up you go. When the water vapor in the rising air gets cold enough, it condenses around “condensation nuclei” in the atmosphere. Condensation nuclei are tiny particles of dust, salt, and other solids that are suspended in the air, similar to the smoke from the match. When enough tiny water droplets form in the atmosphere, we see a cloud in the sky!

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How do colors affect temperature absorption?

How do colors affect temperature absorption?

We’ve all heard the fashion sayings . . . “never wear white after Labor Day” . . . “pastel colors should be worn at Easter” . . . etc. You know the traditions, but did you know they are actually based on science? The color of the clothing you wear can affect how hot or cold you feel when standing outside during the day.

The light reaching us from the Sun is known as “white light” and it is really made up of all the colors of the rainbow. Each of those light rays coming in contains energy. White materials reflect all colors away from their surface, absorbing none of the light energy. Similarly, light pastel colors reflect almost all the incoming light energy. Black materials absorb all light rays, allowing none to be reflected into our eyes. (That’s why it looks “black.”) Dark colors absorb almost all the incoming light energy.

So, you wear light colors in spring and summer to stay cool, and dark colors in the winter to stay warm. Fashion traditions are based on science! You can investigate this phenomenon with your children to prove that it works:

1. Select two t-shirts. Ideally, use one black and one white. If you don’t have black and white, use one that is as dark as possible, and one as light as possible. Also, select t-shirts that are similar in size and fabric type.

2. If possible, do the experiment outside on a warm, sunny day. Select a spot where you can lay the t-shirts out flat, side-by-side. Try not to set them on metal as this will affect the temperature.

3. If you have two similar thermometers, you can just insert a thermometer inside each t-shirt, wait for a select amount of time, and then read the thermometers. Try waiting about 15 minutes and then check for a temperature difference. Increase the time if necessary. Time will depend on the intensity of the sun that day.

4. If you only have one thermometer, try putting some water in two plastic baggies. Be sure to use the same type and size baggie, and the same amount of water. Place one of the baggies of water into each t-shirt at about the same place. Increase the time to about 30 minutes since it will take longer for the water temperature of the water to change noticeably. Be sure to check the temperature of the water in place. Bringing the water into the cool house can drop the temperature significantly while waiting to check the second bag.

To extend the experiment, especially for older children, repeat with different “medium” colors or prints to see what effect each has on temperature. You might also want to test how different types of fabric affect the absorption of light energy. Your children can then write their own “fashion rules” based on science!

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Cotton Cloud Model

Cotton Cloud Model

If you’re teaching your kids about the different types of clouds, have them make a model to show cloud structure and the different levels of the atmosphere where clouds form. Here’s a good website that covers the basics of cloud classification. There’s a good diagram of different types of clouds and the atmospheric levels in which they form. For younger children you might want to let them use the image as a guide for their model. Older children will find it more challenging to only research information about the structure and level of different types of clouds and then develop their own visual model.

Whichever option you choose, provide blue foam board, plenty of cotton balls, school glue, and markers. Challenge your child to plan their model before beginning. Discuss the need to arrange the cotton so that it represents the structure of different types of clouds. And, the need to plan ahead to divide the poster into sections to represent the different levels at which clouds form. A black marker can be used to darken the cotton of the “rain clouds.”

Extend the cloud lesson by taking the finished model outside on different days to identify clouds in the sky. The model will help children understand that they are actually looking up through three different levels of clouds.

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