Energy

Question 1

What is kinetic energy?

Answer 1

Energy stored by movement

Question 2

What is gravitational potential energy?

Answer 2

Energy stored in objects raised above the Earth’s surface - exists because of the Earth’s gravitational field

Question 3

What is chemical energy?

Answer 3

Energy stored by chemical bonds between atoms

Question 4

What is elastic potential energy?

Answer 4

Energy stored by stretching or compressing an object

Question 5

Equation for kinetic energy

Answer 5

Kinetic energy = 1/2 mass x velocity^2

E = 1/2 mv^2

Question 6

Equation for gravitational potential energy

Answer 6

Gravitational potential energy = mass x gravitational field strength x height
E = mgh

Question 7

Equation for elastic potential energy

Answer 7

Elastic potential energy = 1/2 spring constant x extension^2

E = 1/2 ke^2

Question 8

What is specific heat capacity?

Answer 8

Energy needed to raise temperature of 1 KG by 1℃

Question 9

Equation for change in thermal energy (specific heat capacity)

Answer 9

Change in thermal energy = mass x specific heat capacity x change in temperature
∆E =mc∆T

Question 10

Required Practical 1: Specific heat capacity

Answer 10

1. Measure mass of object
2. Heat it up for 2 minutes
3. Work out energy from power and time
4. Work out specific heat capacity

Question 11

Energy transfer of arrow shot from top of city wall

Answer 11

Gravitational potential → mostly kinetic + a bit of thermal

Question 12

What happens when work is done on an object?

Answer 12

Energy is transferred to the object

Question 13

Energy transfer of a racing driver starting their car

Then when they crash because the other driver went the wrong way

Answer 13

Chemical → kinetic + sound + thermal

Kinetic → lots of sound + thermal + potential (both cars)

Question 14

What is efficiency?

Answer 14

How good a device is at transferring energy input to useful energy - if energy is wasted then it is dissipated in useless ways, e.g. sound or thermal energy, but if it is used for the intended purpose it is useful

Question 15

Equation for efficiency

Answer 15

Efficiency = Useful energy/power output ÷ total energy/power input x 100

Question 16

What is power?

Answer 16

Rate of work done or energy transferred

Question 17

Equation for power

Answer 17

Power = work done/energy transferred ÷ time
P = E/t

Question 18

Insulation in a house

Answer 18

• Thicker walls, use material with low thermal conductivity
• Cavity wall insulation - air gap between walls filled with foam which has trapped air, prevents convection
• Double glazing - 2 layers of glass with air gap too small for air circulation, prevents convection
• Fit carpets to reduce heat loss from floors

Question 19

Required Practical 2: Thermal Insulation

Answer 19

1. Boil water
2. Pour into beaker with 0 layers of newspaper (control)
3. Measure temperature, repeat every 5 minutes
4. Do again with different layers of newspaper
5. Plot cooling curve graph - more insulation should mean slower cooling
6. Repeat whole experiment but changing material for insulation this time

Question 20

What are renewable and non-renewable energy resources?

Answer 20

Non-renewable energy resources will eventually run out

Renewable energy resources will not run out

Question 21

Hydroelectric

Answer 21

Generators in dams use moving water to drive turbines

Advantages:
• Renewable
• No gas emissions
• Cheap to run

Disadvantages:
• Initially expensive
• Limited suitable locations - needs enough water and land to create a reservoir
• Floods animal habitats and farmland

Question 22

Wind

Answer 22

Uses kinetic energy of wind to turn a turbine
Advantages:
• Renewable
• No gas emissions
• No fuel costs

Disadvantages:
• Low power output from each turbine
• Unreliable – they only work when it is windy
• Visual pollution for some

Question 23

Solar

Answer 23

Solar (photovoltaic) cells convert sunlight to electricity

Advantages:
• Renewable
• No gas emissions
• No fuel costs

Disadvantages:
• Expensive to produce the panels
• Low power output
• Unreliable supply – they do not work at night

Question 24

Geothermal

Answer 24

Uses underground rocks (heated up by lava) to heat up water into steam which turns a turbine

Advantages:
• Renewable
• No gas emissions
• No fuel costs

Disadvantages:
• Expensive to build
• Limited suitable locations - needs hot rocks near the surface

Question 25

Wave and tidal

Answer 25

Uses motion of waves in the sea or the movement of tides to turn turbines

Advantages:
• Renewable
• No gas emissions
• No fuel costs

Disadvantages:
• Limited suitable locations - coastal areas only
• Installing turbines and generators interferes with other activities (fishing, swimming etc.) and/or wildlife

Question 26

Biofuel

Answer 26

Uses heat from burning biofuels (from (recently) living organisms) to heat water into steam which turns a turbine

Advantages:
• Renewable
• Suitable for remote/rural locations
• Carbon neutral - the carbon used by the organism when it was living equals the carbon released when it is burned

Disadvantages:
• Biofuels release carbon dioxide when burned.
• Low power output – only suitable for small scale use

Question 27

Fossil fuels

Answer 27

Uses heat from burning coal, oil or gas to heat water into steam which turns a turbine

Advantages:
• High power output

Disadvantages:
• Non-renewable
• Carbon dioxide, sulfur dioxide and nitrogen oxides released into the atmosphere when burned
• Oil spills are environmental disasters (oil only)

Question 28

Nuclear

Answer 28

Uses nuclear fission releases energy to heat water into steam which turns a turbine

Advantages:
• No waste gases produced
• Large power output from a small amount of fuel

Disadvantages:
• Radioactive waste produced
• Power stations expensive to build and decommission
• Nuclear meltdowns