The Digital Bits Science Labs are fun science experiments for young children. Kids, make sure you have an adult's permission before trying any of these science experiments.
Digital Bits Science Lab
Science Experiments for Kids, Parents and Teachers
When heated, air will expand. When cooled, air will compress. Hot air takes up more space than cold air, as this experiment demonstrates.
A plastic soda bottle (a 2-liter will work well)
A soup pot
The Digital Bits Science Lab Experiment:
Pour some water into the bottle. Three inches or so will be plenty.
Pull the ballon over the mouth of the bottle. The balloon should be deflated at this point. Wrap a strip of duct tape around the balloon-bottle connection, to make sure the seal is close to airtight.
Fill the soup pot with water. An inch or so will be plenty.
Put the bottle in the soup pot. Put the pot on the stove.
Turn on the stove. You should have something that looks like this:
Wait for the water in the pot to heat up. As it does, the water in the bottle will heat, too. The balloon will eventually inflate:
What’s happening? This science experiment demonstrates how air, when heated, will expand. It expands because air molecules move around a lot more when warmed up. Since they’re moving around more, they bounce around and off each other, and take up more room. We see this as the balloon expands.
To see the opposite of this effect, take the bottle-balloon invention off of the stove. Place it in a container full of ice, or stand it up in a freezer. The balloon will shrink back down and deflate, and the bottle itself might compress inward as the air gets colder!
Another question that people may have is, “why doesn’t the plastic bottle melt on the stove?” Here’s an experiment that shows why the bottle won’t melt, because the water conducts the heat away from the bottle.