The purpose of a car engine is to transform the chemical energy of gasoline into kinetic energy of the car in motion. Gasoline is burned in the engine to create that movement. However, gasoline engines are typically only about 20% efficient. What happens to the rest of the energy released from the burning gasoline?

heat

Explanation:

most of the gasoline's energy is released as heat energy rather than kinetic energy on the pistons. this is why a car engine must constantly be cooled by the water to air heat exchanger we call a radiator

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.