Topic 3 - Conservation Of Energy

Question 1

Give an example of Chemical energy, kinetic energy, thermal objects, elastic potential energy, gravitational potential energy and nuclear/atomic energy.

Answer 1

Chemical energy - Energy stored in food, batteries and fuel
Kinetic energy - energy stored in moving objects
Thermal energy - energy stored in hot objects
Elastic potential energy - stretched, squashed or twisted materials
Gravitational potential energy - Objects in high positions
Atomic/nuclear energy - Energy stored inside an atom

Question 2

What is the law of conservation of energy?

Answer 2

Energy cannot be created or destroyed

It can only be transferred from one store to another

Question 3

What are the units for measuring energy?

Answer 3

Joules (J)

Question 4

How do you represent energy stores and transfers?

Answer 4

Diagrams like this:

Energy stored in Energy transferred by Energy stored in
moving car ——————————————> Hot brakes
(Kinetic energy) Forces during braking (Thermal energy)

Question 5

How do you show the amount of energy transferred?

Answer 5

Sankey diagrams

Question 6

What happens to energy when it is wasted during a transfer?

Answer 6

The energy is dissipated (spread out) and cannot be used for other useful energy transfers

Question 7

How can friction be reduced?

Answer 7

Lubricant

Question 8

What is efficiency ?

Answer 8

A way of describing how good a machine is at transferring energy into useful forms.

Number between 0 and 1

Higher the number, more efficient the machine.

Question 9

How can efficiency of a device be calculated?

Answer 9

Useful energy transferred by the device
Efficiency = —————————————————
Total energy supplied to device

Question 10

How can you increase efficiency i.e. in mechanical processes?

Answer 10

Reduce amount of wasted energy
E.g. Reduce friction in mechanical processes
Also make sure all fuel is burned or find a way of using the excess heat

Question 11

What is insulation?

Answer 11

Insulation slows down the rate at which energy is transferred out of a house by heating.

Question 12

He can energy be transferred by heating in conductors?

Answer 12

• In conduction, vibrations are passed in between particles in a solid.
• Metals are good thermal conductors and materials such as wood or poor thermal conductors. (Good thermal insulators)

Question 13

How can Energy be transferred by heating in a convection?

Answer 13

In convection, part of a fluid that is warmer than the rest, rises and sets up a convection current.

Question 14

How can Energy be transferred by heating by Radiation?

Answer 14

Radiation is the only way in which energy can be transferred through a vacuum.
Infrared radiation can also pass through gases and some solid materials.
Infrared radiation is absorbed and emitted easily by dull, dark surfaces, and is absorbed and emitted poorly by light, shiny surfaces.

Question 15

What is thermal conductivity?

Answer 15

Energy is not transferred through very easily by heating

Question 16

How does thickness, conductivity and temperature affect energy transfer?

Answer 16

Rate of energy transfer is reduced by:

• Increasing thickness
• Decreasing thermal conductivity
• Decreasing temperature difference

Question 17

What is Gravitational potential energy?

Answer 17

Energy that is stored because of an object’s position in a gravitational field.

• Any object that is above the surface of the Earth contains a store of gravitational potential energy
• Every time something is moved upwards, it stores more gravitational potential energy

Question 18

What is the equation for the change in gravitational potential energy?

Answer 18

Change in gravitational
potential energy = mass x gravitational x change in vertical
(J) (Kg) field strength height
(N/kg) (m)

Question 19

What is most electricity in the Uk generated from?

Answer 19

Nuclear fuels or fossil fuels {coal, oil and natural gas}

Question 20

What does non-renewable mean?

Answer 20

Energy sources that will run out {we can’t produce them at a rate we can replace them}

Question 21

What are fossil fuels used for?

Answer 21

Petrol and diesel > Vehicles, aeroplanes and ships because they store a lot of energy and are easy to store in engines.
Natural gas > Burnt to heat homes or cooking

Question 22

How do fossil fuels affect climate change ?

Answer 22

Burning fossils fuels emit carbon dioxide and other gases.

Carbon dioxide emissions contribute to climate change by warming the atmosphere.

Question 23

What other problems do Fossil Fuels cause?

Answer 23

Cause pollution problems and reducing pollution costs a lot of money.
Burning natural gas causes less pollution than burning coal.
Therefore, power stations with natural gas cause less pollution than those with coal, when producing the same amount of electricity

Question 24

How are nuclear power stations beneficial and bad?

Answer 24

Don’t emit any carbon dioxide.
Not many accidents as designed to contain radioactive leaks

However, when one does happen it causes bad consequences.
Waste they produce is very radioactive and will stay that way for millions of years.
This is expensive to dispose of safely.
Very expensive to decommission (dismantle safety) a nuclear power station when it is done with.
Costs a lot more to build and decommission a nuclear power station than a fossil fuelled one.

Question 25

What are renewable sources?

Answer 25

Energy resources that will not run out

Question 26

How is solar energy renewable?

Answer 26

Solar cells convert solar energy directly into electrical energy.
Can be used to fuel homes or power stations with electricity.
Can also be used to heat water for use in homes.
Not available all the time.

Question 27

How is hydro electricity renewable?

Answer 27

Generated by falling water in laces where water can be trapped in high reservoirs.
Available at any time as long as the reservoir doesn’t dry up
A hydroelectric power station can be started and stopped very quickly unlike fossil fuel stations.

Question 28

How are wind turbines renewable?

Answer 28

Can be used to generate electricity as long as the wind speed is not too low or too fast.
A lot are needed to produce same amount as fossil fuels stations would.
Spoil landscape.

Question 29

How is tidal power renewable?

Answer 29

Generate electricity when turbines in a huge barrage (dam) ,across a river estuary, turn as the tides flow in and out.
Not available all time but can be predicted.
There are not many places to crest barrages.
Can affect birds and other animals that live or feed on tidal mudflats.
Underwater turbines can be placed in water currents in the sea to generate electricity

Question 30

How are bio-fuels renewable?

Answer 30

Made from animal wastes or from plants.
Bio-fuels can be made from waste food or the parts of plants that are not used for food, but some crops are grown specifically for bio-fuels.
They are carbon neutral because when they burn, they emit the same amount of carbon dioxide they took in.
However, energy is also needed to grow and harvest the crops and turn them into fuel.
So they aren’t really carbon neutral.

Question 31

Why can’t we not just depend on renewable sources?

Answer 31

They are not available all year round.

Takes a lot of land area to produce some.