Today at Weather Watchers we investigated what happens to air when you heat it and cool it down. We put a balloon on top of an empty bottle and put the bottle in hot water. We saw the ballon blow up all on its own! Then we put the bottle in some ice and watched the balloon deflate into the bottle! So, we discovered that when you heat air it expands and when you cool it, air compresses. You can try our experiment at home!