Topic 2: Conservation of Energy

Question 1

What are the 4 main ways that energy can be transferred between stores?

Answer 1

Mechanically - e.g. pushing
Electrically - e.g. charges moving round a circuit
By heating - e.g. heating a pan on a hob
By radiation (transferred by waves) - e.g. energy from sun reaching earth by light

Question 2

Explain in term of energy transfers a bat hitting a ball

Answer 2

The bat has energy in its kinetic energy store. Some is transferred mechanically to the ball’s kinetic energy store. Some energy is transferred mechanically to the bat and ball’s thermal energy stores (and then dissipates into the surroundings by heating). The rest is carried away by sound

Question 3

How can you calculate efficiency?

Answer 3

Efficiency = useful energy transferred / total energy transferred

Question 4

What are the two main ways to increase efficiency?

Answer 4

Lubrication
Thermal insulation

Question 5

What’s lubrication?

Answer 5

• Reduces energy transferred by friction
• So, less energy is transferred mechanically to the thermal energy store of the object
• Usually liquids e.g. oil so they can flow easily between objects and coat them

Question 6

What’s insulation?

Answer 6

• Reduces the rate of energy transferred by heating
• Cavity walls in buildings reduce the amount of energy transferred by conduction because there is an air gap in the middle and air has a very low thermal conductivity
• Thicker walls help as well to slow the rate of energy transfer
• Insulation lowers the thermal conductivity

Question 7

What is conduction?

Answer 7

• When one side of an object is heated, particles in the hotter part vibrate more and collide with each other with transfers energy from their kinetic energy stores to other particles which then vibrate faster
• This transfers energy through the object

Question 8

What are the three main fossil fuels?

Answer 8

Coal
Oil
(Natural) Gas

Question 9

What are fossil fuels?

Answer 9

Natural resources that form underground over millions of years that are typically burnt to provide energy

Question 10

What are 2 examples of non-renewable energy resources?

Answer 10

Fossil fuels
Nuclear fuel

Question 11

What environmental problems do fossil fuels create?

Answer 11

• release carbon dioxide into atmosphere when burned, adds to greenhouse effect + contributes to global warming
• burning coal and oil can release sulfur dioxide which causes acid rain (can be reduced by taking sulfur out before fuel is burned)
• oil spillages affects mammals and birds that live around the sea
• nuclear waste is difficult to dispose of

Question 12

What are 5 examples of renewable energy resources?

Answer 12

• Wind
• Sun (solar)
• Bio-fuels
• Tides
• Hydro-electricity

Question 13

What’s one disadvantage of renewable energy resources?

Answer 13

They don’t provide much energy, some are unreliable (because they’re weather dependent)

Question 14

What’s one disadvantage of renewable energy resources?

Answer 14

They don’t provide much energy, some are unreliable (because they’re weather dependent)

Question 15

What are Bio-fuels?

Answer 15

• Renewable energy resources created from plant products/animal dung and can be burnt to produce electricity
• Supposedly carbon neutral
• Reliable: Crops take short time to grow, different crops can be grown all year round
• Can’t respond to immediate energy demands
• Expensive and takes up space so food crops can’t meet demands
• Damage to natural habitats and CO2 emissions when clearing forests to make room for growing biofuels

Question 16

Explain wind power, solar cells, hydro electricity and tidal barrages (if you get time before exam)