2.1 Energy Stores & Systems

Question 1

What is the most important rule to note about energy?

Answer 1

Energy is never created or destroyed, it is only transferred between different forms and objects.

Question 2

What are all the different energy stores? (8)

Answer 2

1) Thermal energy stores: the heat energy trapped within an object and is related to the temperature of the object.
2) Kinetic energy stores: the movement or motion of an object.
3) Gravitational potential energy stores: the energy that an object possesses because of its position in a gravitational field.
4) Elastic energy stores: the energy held in an already-stretched spring.
5) Chemical energy stores: held in chemical bonds.
6) Nuclear energy stores: what we get from breaking atoms apart.
7) Electromagnetic energy stores: two objects will have energy in this store if they exert a magnetic force on each other.
8) Electrostatic energy stores: two objects will have energy in this store if they exert an electrostatic force on each other.

Question 3

What is a ‘system’?

Answer 3

A system is a fancy word for a single object (e.g. the air in a pistol) or a group of objects (e.g. two colliding vehicles) that you’re interested in. A system can be changed by heating or working.

Question 4

What takes place in an open system?

Answer 4

The matter of the system can exchange energy with the ‘outside world’ (all of the matter which is outside of our system). This means that an open system can lose or gain energy as it interacts with the outside world.

Question 5

What takes place in a closed system?

Answer 5

A closed system is separate from the ‘outside world’ so neither matter nor energy can enter or leave. So even though energy can be transferred within the system, the overall change is always zero.

Question 6

Describe the two ways in which energy can be transferred by heating

Answer 6

• Conduction is where the vibrating particles of a substance transfer energy to neighbouring particles.
• Convection is where the energetic particles of a substance move away from hotter to cooler regions.

Question 7

What are the two different ways that work can be done?

Answer 7

• Mechanically (an object moving due to a force doing work on it, e.g. pushing, pulling or stretching)
• Electrically (a charge doing electrical work against resistance, e.g. charges moving around a circuit).

Question 8

How is transferring energy by electricity from a power station to consumers convenient?

Answer 8

It can travel over long distances.

Question 9

Describe how a battery-operated heater works

Answer 9

Energy is transferred electrically from the chemical energy store of the battery to the thermal energy store of the electric heater. This energy is then transferred to the surroundings by heating.

Question 10

Describe how a motor connected to the mains works

Answer 10

In a power station, energy is transferred from the chemical energy store of the fuel to the thermal energy store of water in the boiler. This is then transferred to the kinetic energy stores of turbines and generators which produce electricity. Energy is transferred by the electric current (electrically) to the kinetic energy store of the motor.

Question 11

List the 5 different ways that energy can be transferred:

Answer 11

• Mechanically
• Electrically
• Through heating
• Via infrared radiation
• Via light or sound waves

Question 12

When you throw a ball up in the air, it moves through a gravitational field. Why does it slow down?

Answer 12

Energy from its kinetic energy store is being transferred to its gravitational potential energy store.

Question 13

How is energy transferred away from a lightbulb? (2)

Answer 13

• Via light
• By heating