What process does a hot-air balloon rises and a thermometer measures temperature?

A hot-air balloon rises due to the principle of buoyancy, where warmer air inside the balloon is less dense than the cooler air outside, causing it to float. The air is heated by a burner, which increases its volume and reduces its density. A thermometer measures temperature by using a liquid (like Mercury or alcohol) that expands or contracts in response to temperature changes, indicating the degree of heat. Both processes rely on the properties of gases and their behavior when subjected to temperature changes.