Identify the method of thermal energy transfer at work in hot air balloons. explain how thermal energy is transferred in this scenario.

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. 

Convection is the method through which thermal energy in air can be transferred.

As the thermal energy converted into kinetic energy in particles hot air usually rises, which causes the particles to move faster and further apart, causing hot air to be less dense and therefore rises. Cold air has less thermal energy to transfer into kinetic energy, which causes particles to not move as fast and closer together, causing cold air to be more dense and sinks. Now for the example of hot air balloons, the pilot heats the air and as the air gets hotter the balloon will expand which causes its density to drop, therefore floating above the cold air.

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It indicates no change in temperature and the process of matter changing its state