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Cold Weather Science
January 21, 2013 - Jen Zbozny
Recently I wrote about showing kids what a chemical suspension is by using borax to make crystallized snow flakes. This week's super cold temperatures inspire me to share some simple science that will be perfect in this weather. You can give your kids a great demonstration of how a gas contracts (and pressure decreases) when it cools, and expands (and pressure increases) when a gas is warmed. It only takes a balloon!
Here's what to do.
Blow up a balloon and tie it shut. If you already have a Mylar balloon from the grocery store or a well-inflated balloon on a stick, those work perfectly because the stick really shows the change in the balloon and the Mylar is stiffer than regular balloon material.
Have your kids feel the balloon and pay attention to how tightly the balloon is stretched out. If your kids are older, you can even use a tape measure or length of string to record the circumference of the inflated balloon inside the house. It's important to observe this in the warm house.
Now, take the balloon and secure it outside, preferably near a window where you can see it. I used a clothes pin and secured our balloon close to our kitchen door.
What happens now is that the air inside the balloon cools. When it cools, it contracts and the pressure decreases. That makes your balloon look droopy. Since its so cold, you won't have to wait long to see it begin to happen. In about 20 minutes you can see that your balloon looks droopy. It hasn't actually lost much air. The air inside it has cooled and the pressure (which is what makes the balloon nice and plump) has fallen. That makes the balloon sad.
Next comes the chilly part. If your kids can't see the balloon well, or if you want your kids to have the tactile and visual understanding of the contracted gas inside the balloon, you may have to go outside to touch or measure it. Once you've finished touching and measuring - hurry up and go inside with the balloon.
Get yourself warm and watch the balloon get warm too. As the air inside the balloon warms, it will expand. That will perk your balloon right back up. Voila! Simple science with cold weather and a balloon. Keep warm and stay curious!
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