Do you know that some people fly on a bag of hot air? Of course, the “bag” is a huge hot-air balloon. A balloon filled with hot air can lift people.
When air is heated, its molecules speed up and begin to push on one another. This makes the air expand, or take up more space. The molecules of hot air push further and further apart until only a few molecules take up a great deal of space.
The molecules of hot air that fill a balloon are further apart than the molecules of colder air outside the balloon. So the hot air weighs much less than the colder air. Because the hot air is lighter, it rises. It pushes up inside the balloon. When the push is strong enough, it lifts the balloon high into the sky.
Ask a grown-up to heat a toaster. Standing I metre away from the toaster, blow soap bubbles so that they float above it. Watch the bubbles rise as they reach the hot air above the toaster! Be careful not to get the toaster wet! Electricity and water are dangerous together!
Picture Credit : Google