energy stores and transfers

define a system

An object or group of objects

What happens when a system is in equilibrium?

When a system is in equilibrium, nothing changes and so nothing happens

What happens when there’s a change in system?

When there is a change in a system, things happen, and when things happen energy is transferred

What is energy measured in?

joules (J)

What are the 3 states of a thermodynamic system?

isolated, closed or open

What can happen in an open system?

An open system allows the exchange of energy and matter to or from its surroundings

What can happen in a closed system?

A closed system can exchange energy but not matter to or from its surroundings

What can happen in an isolated system?

An isolated system does not allow the transfer of matter or energy to or from its surroundings

where is energy stored?

Energy is stored in objects

What happens when a change happens within a system?

When a change happens within a system, energy is transferred between objects or between stores

State the conservation of energy

Energy cannot be created or destroyed, it can only be transferred from one store to another

Describe the total amount of energy in a closed system

This means that for a closed system, the total amount of energy is constant.

Describe kinetic energy stores

Moving objects have energy in their kinetic store

Describe gravitational energy stores

Objects gain energy in their gravitational potential store when they are lifted through a gravitational field

Describe elastic energy stores

Objects have energy in their elastic potential store if they are stretched, squashed or bent.

Describe magnetic energy stores

Magnetic materials interacting with each other have energy in their magnetic store

Describe electrostatic energy stores

Objects with charge (like electrons and protons) interacting with one another have energy in their electrostatic store

Describe chemical energy stores

Chemical reactions transfer energy into or away from a substance's chemical store

Describe nuclear energy stores

Atomic nuclei release energy from their nuclear store during nuclear reactions

Describe thermal energy stores

All objects have energy in their thermal store, the hotter the object, the more energy it has in this store

How many types of energy store is there?

8

List all types of energy stores

• kinetic

• gravitational

• elastic

• magnetic

• electrostatic

• chemical

• nuclear

• thermal

through what is energy transferred between?

Energy is transferred between stores via transfer pathways

How many transfer pathways are there (that we need to know)

• Mechanically

• Electrically

• By heating

• By radiation

describe mechanical working transfer pathway. give 4 examples

When a force acts on an object (e.g. pulling, pushing, stretching, squashing)

describe electrical working transfer pathway. give 1 example

A charge moving through a potential difference (e.g. current)

describe heating (by particles) transfer pathway. give 1 example

Energy is transferred from a hotter object to a colder one (e.g. conduction)

describe (heating by) radiation transfer pathway. give 1 example

Energy transferred by electromagnetic waves (e.g. visible light)

describe the energy transfer that occurs when a hot coffee in a mug is heating up cold hands (3)

• system - coffee, mug and hand

• energy is transferred by heating from the coffee’s thermal store to the mug’s thermal store

• energy transferred by heating from mug’s thermal store to hand’s thermal store

what are the 3 steps in describing an energy transfer?

Step 1: Determine the store that energy is being transferred away from

Step 2: Determine the store that energy is transferred to

Step 3: Determine the transfer pathway

describe the energy transfer that occurs when a battery powers a torch (4)

1. The system is the battery and torch, so the energy transfer to focus on is from the battery to the bulb.Therefore, the energy begins in the chemical store of the cells of the battery

2. When the circuit is closed, the bulb lights up. Therefore, energy is transferred to the thermal store of the bulb.

3. Energy is transferred by the flow of charge around the circuit. Therefore, the transfer pathway is electrical.

Energy is transferred electrically from the chemical store of the battery to the thermal store of the bulb

describe the energy transfer that occurs when a ball is falling (8)

1. For a ball falling, the system is defined as the ball 

2. In order to fall, the ball must have been raised to a height

3. Therefore, it began with energy in its gravitational potential store

4. As the ball falls, it is moving

5. Therefore, energy is being transferred to its kinetic store

6. For an object to fall, a resultant force must be acting on it, and that force is weight and it acts over a distance (the height of the fall)

7. Therefore, the transfer pathway is mechanical

Energy is transferred mechanically from the gravitational potential store of the ball to the kinetic store of the ball