Thermal energy in the form of fire is generated by the combustion of fuel. Due to the tendency of hot air to rise upward, the heat generated rises to fill the space of the balloon. One this space is full of trapped hot air, the heat's tendency to rise causes the hot air balloon to be lifted into the air.
Sample Response: Convection is the method of thermal energy that occurs in hot air balloons. Thermal energy is transferred when the air above the flame becomes warm and less dense, and rises. Cool, dense air sinks and takes the place of the warm air that rises. The cool air is warmed by the flame, becomes less dense, and rises. This cycle continuously warms up the air in the balloon.
