Visualize heat getting converted into work
To visualize work done by the heat.
Heat can be used to do work i.e., heat is a form of energy.
glass bottle with small opening, a coin
Add some water in the bottle. Place a wet coin on its mouth. Rub your palms vigorously and hold the bottle between them. Closely watch the coin. It jumps (a bit) up and down for a few times.
Air inside the bottle is cool. When it is brought between the palm, air inside the bottle gradually starts warming up. It expands and looks for an outlet. Pushing the coin it makes an escape.