Question

Tracy makes a list of energy transformations that occur as an engine runs to power a car.

1. Chemical energy transforms into thermal energy.
2. Thermal energy transforms into electrical energy.
3. Chemical energy transforms into gravitational potential energy.
4. Thermal energy transforms into kinetic energy.

Which transformation should Tracy remove from the list?

Answer 1

3. Chemical energy transforms into gravitational potential energy.

Explanation:

First of all, let's check the definition for each type of energy:

- Chemical energy is the energy stored in the chemical bonds inside compounds and substances

- Thermal energy is the energy due to the random motion of atoms/molecules (heat)

- Electrical energy is the energy related to the motion of electrical charges

- Gravitational potential energy is the energy of an object which is placed at some height above the ground

- Kinetic energy is the energy of an object in motion

Given this definition, we can check each energy transformation to see which one are really involved in the engine used to power the car:

1. Chemical energy transforms into thermal energy. --> YES. This one is present: in fact, the chemical energy contained in the fuel is converted inside the engine into heat (thermal energy)

2. Thermal energy transforms into electrical energy. --> YES. The heat (thermal energy) used in the engine is converted into electrical energy used to turn on the car.

3. Chemical energy transforms into gravitational potential energy. --> NO. There is no gravitational potential energy involved in this example, since the car runs on the ground.

4. Thermal energy transforms into kinetic energy. --> YES. The heat (thermal energy) used in the engine is converted into energy of motion of the car.

Therefore, Tracy should remove option 3) from her list.

Answer 2

Answer: The correct answer is "Chemical energy transforms into gravitational potential energy".

Explanation:

In the given problem, an engine runs to power a car. The internal combustion engine in the car is gasoline which converts chemical energy into the thermal energy. Then, this thermal energy gets converted into kinetic energy by causing to power a car.

The chemical energy is obtained from the fuel which is in an engine of the car converts into thermal energy.

The thermal energy is generated in an engine of the car converts into the electrical energy so that the car can be started.

There is no use of gravitational potential energy in a car as it is due to the height above the ground.

Therefore, the correct option is (3).