Question

Describe how energy is changed from one form to another in these processes: (a) At a July 4 th celebration, a match is lit and ignites the fuse of a rocket firecracker, which fires off and explodes at an altitude of \(1000 \mathrm{ft}\). (b) A gallon of gasoline is pumped from an underground storage tank into the fuel tank of your car, and you use it up by driving \(25 \mathrm{mi}\).

Short answer

Chemical energy converts to thermal, sound, kinetic in explosions; gasoline converts chemical to mechanical in cars.

Step-by-step solution

Energy Conversion in Lighting a Match

When a match is lit, the chemical energy stored in the match head is converted into thermal (heat) energy due to friction. This heat energy ignites the match.

Igniting the Rocket Firecracker

The thermal energy from the match ignites the chemical substances in the rocket firecracker's fuse. This chemical energy is transformed into thermal energy and then into kinetic energy as the rocket propels itself upwards.

Rocket Explosion

At the apex of its trajectory, the firecracker's kinetic and potential energy is converted back into thermal energy and sound energy during the explosion at 1000 ft altitude. This demonstrates energy conversion from chemical to kinetic to thermal and sound energy.

Pumping Gasoline into Car

During the transfer of gasoline from the underground storage to the car's fuel tank, the mechanical energy of the pump is used to move the gasoline without significant energy transformation taking place.

Converting Gasoline Energy to Motion Energy

In the car engine, the chemical energy of gasoline is converted into thermal energy through combustion, which generates pressure. This thermal energy is converted into mechanical energy, propelling the car forward to cover the 25-mile distance.

Key concepts

Chemical Energy

Chemical energy is stored in the bonds between atoms within molecules and it plays a significant role in various energy transformations. When you strike a match against a rough surface, you're creating friction. This friction provides the initial thermal energy required to break the chemical bonds in the match head. The atoms within the chemicals rearrange and release energy, igniting the match. Similarly, in the case of a rocket firecracker, chemical reactions within the fuse and the firecracker's explosive material release stored chemical energy, driving the transformation into other forms like thermal and kinetic energy.
In car engines, it's the chemical energy of gasoline that gets transformed into motion. Combustion inside the engine breaks chemical bonds, releasing energy that becomes the powerhouse for the vehicle. Every time you drive, this conversion from chemical to mechanical energy occurs due to the potential energy stored in gasoline.

Thermal Energy

Thermal energy, often referred to as heat energy, is all about the motion of particles within a substance. The more frantic these movements are, the hotter the substance is.
When lighting a match, the friction generated results in thermal energy. This thermal energy is crucial for igniting the chemical substances in the match head and later in the firecracker fuse.

• Thermal energy results from friction, as seen in striking a match.
• It's essential for igniting substances that lead to explosions or combustion.

In the car's engine, thermal energy from burning gasoline creates pressure. This pressure causes the pistons to move, transforming into mechanical energy needed to drive the car. So, whenever there's combustion, thermal energy is a key player.

Kinetic Energy

Kinetic energy is the energy of motion; whenever an object is moving, it possesses kinetic energy. In the example of the rocket firecracker, as soon as the firecracker is ignited, the thermal energy causes it to move upward.

• Kinetic energy increases with the firecracker's speed.
• It’s observable when the firecracker ascends to 1000 ft.

In the context of a moving car, all the intricate mechanical parts are brought into motion, converting thermal energy from gasoline combustion into kinetic energy.
Every time you accelerate or maintain speed, kinetic energy is being harnessed, enabling you to cover distances like 25 miles.

Mechanical Energy

Mechanical energy is the sum of an object's kinetic and potential energy. It relates to the motion and position of an object in its environment.
When looking at the process of pumping gasoline, mechanical energy is employed. The pump moves gasoline from the storage tank to the fuel tank based purely on mechanical principles. Although no significant energy transformation occurs during this specific movement, mechanical energy is essential for facilitating it.
In a car’s engine, mechanical energy is the final product of various energy transformations. The engine transforms the heat generated by gasoline into motion, moving the car forward. All engine components, including pistons and wheels, work in unison, thanks to mechanical energy, allowing a seamless drive across distances.