P1 : Energy

What is a system?

An object or group of objects

What happens when a system changes?

Energy is transferred

What is the difference between an open system and a closed system?

An open system can gain and lose energy to the surroundings whereas a closed system can only transfer energy within the system and cannot gain or lose energy (the overall change in energy is always 0)

What are the 8 energy stores?

• Gravitational potential energy store

• Electrostatic energy store

• Thermal energy store

• Magnetic energy store

• Elastic potential energy store

• Nuclear energy store

• Chemical energy store

• Kinetic energy store

Explain gravitational potential energy store

The energy an object has in relation to its position in a gravitational field/earths surface

Explain electrostatic energy store

Energy of negative and positive ions

Explain thermal energy store

Related to temperature, basically heat energy

Explain magnetic energy store

Energy in a magnetic field

Explain elastic potential energy store

Energy when something is stretched or squashed

Explain nuclear energy store

Energy from breaking atoms apart

Explain chemical energy store

Held in chemical bonds

Explain kinetic energy store

Movement or motion of an object

What are the 4 ways energy is transferred?

• Heating

• Electrically

• Radiation

• Mechanically

What happens when energy is transferred by heating to an object?

The object changes temperature

What happens when energy is transferred electrically to an object?

A current flows through the object

How is energy transferred by radiation?

Energy transferred as a wave, e.g. light and infrared

What happens when energy is transferred mechanically to an object?

The object moves or a force has been applied to it

In terms of kinetic energy, when is energy transferred to an object?

When it speeds up

In terms of kinetic energy, when is energy transferred away from an object?

When it slows down

What 2 factors does kinetic energy store depend on?

• Mass

• Speed

What is the formula for kinetic energy?

½ x m x v^²

When is energy transferred to an object in terms of gravitational potential energy?

When an object is being lifted

What 3 factors does gravitational potential energy depend on?

• Mass

• Height

• Gravitational field strength

What is the formula for gravitational potential energy?

m x g x h

When a falling objects has no air resistance what is the formula in terms of g.p.e and k.e

What is the formula for elastic potential energy?

½ x k x e²

What is work done?

When a force moves an object through a distance, energy is transferred and work is done

What is the formula for work done?

f x s

Explain the energy transfer of a ball being thrown upwards + when work is done (2)

• The initial force of a person to throw a ball does work.

• Energy is transferred mechanically from the chemical energy store of the arm to the kinetic energy store of the ball.

Explain the energy transfer of a moving car hitting an obstacle + when work is done (3)

• The normal contact force between the car and the object does work.

• Energy is transferred from the kinetic energy store of the car to the other energy stores of the object and the car body.

• Some energy could be transferred as sound waves.

Explain the energy transfer of an object being accelerated by a constant force

Energy is transferred from the chemical energy store of the fuel in the car to the kinetic energy store of the car

Explain the energy transfer of a vehicle slowing down + when work is done (2)

• The friction between the car’s brakes and wheels does work as it slows down

• Energy is transferred from the wheels kinetic energy store to the thermal energy store of the surroundings

Explain the energy transfer of a ball falling down + when work is done (3)

• A ball dropped from its height is accelerated by gravity

• The gravitational force does work

• Energy is transferred from the ball’s gravitational potential energy store to its kinetic energy store

Explain the 2 energy transfers of a kettle heating water

• Energy is transferred to the water by heating into the water’s thermal energy store

• Energy is transferred electrically (when a current flows) from the plug to the thermal energy store of the heating element of the kettle

What is specific heat capacity?

The amount of energy needed to raise the temperature of 1kg of substance by 1°C

What is the equation for specific heat capacity?

ΔE=m x c x ∆θ

What are the units for specific heat capacity?

J/kg°C

Explain how to investigate specific heat capacity (9)

1. Get a block of the desired material with 2 holes in it (one for the heater and one for the thermometer)

2. Measure the mass of the block, then wrap it in an insulating layer (like newspaper) to reduce energy transferred to the surroundings

3. Insert the heater and thermometer into the 2 holes

4. Measure the initial temperature of the block and set the potential difference of the power supply to 10V

5. Turn on the power supply and start a stopwatch

6. As the block heats up take readings of the temperature and current every minute

7. After 10 minutes turn the power supply off and calculate power using P=VI then use E=Pt to calculate the energy transferred to the heater

8. plot a graph and find the gradient. This would be ∆θ/ΔE then the shc is 1/(gradient x mass of the block)

9. Repeat this experiment with different materials

What is the conservation of energy principle?

Energy cannot be created or destroyed, only stored or transferred

What is dissipated energy?

Wasted energy that wasn’t transferred to the desired energy store

What is the energy transfer in a mobile phone? (useful and dissipated in an open system) (2)

• Energy is usefully transferred to the chemical energy store of the battery in the phone

• But some of the energy is dissipated in this transfer to the thermal energy store of the phone causing it to heat up

What is power?

The rate of energy transfer or work done

What is the equation for power in terms of energy transfer?

P = E/t

What is the equation for power in terms of work done?

P=W/t

What does one watt equal to?

1 Joule of energy transferred per second

What does a powerful machine do?

Transfer a lot of energy in a short space of time

What state of matter does conduction take place in?

Solids

What is the definition of conduction?

The process where vibrating particles transfer energy

Explain conduction (5)

• Energy is transferred to the thermal energy store of the object by heating

• This energy is shared across the kinetic energy stores

• The particles vibrate more and collide with each other

• Collisions lead to energy being transferred between particles’ kinetic energy stores

• This process continues until the whole object has been warmed up

What is thermal conductivity?

The measure of how quickly energy is transferred through a material

What state of matter does convection take place in?

Liquids and gases

What is the definition convection?

When energetic particles move away from hotter regions into cooler regions

Explain convection? (5)

• Energy is transferred to the thermal energy store of the particles by heating

• This energy is shared across the kinetic energy store of the particles

• The particles start to move faster and the space between the particles increase + density decreases

• The warmer, less dense particles will then move to the cooler, dense regions

• This process repeats leading to a convection current

What are the 2 ways to reduce unwanted energy transfers?

• Lubrication

• Thermal insulation

Why is friction bad in terms of unwanted energy transfers?

Because friction causes energy to be dissipated to the thermal energy store of objects and surroundings

What do lubricants do?

Reduce friction

Give an example of a lubricant

Liquids (oil)

What does thermal insulation do?

Prevent thermal energy from escaping

Explain 6 examples of thermal insulation in houses + how they work

• Thick walls - made from a low thermal conductivity material keep heat in

• Loft Insulation - reduce currents created in lofts

• Cavity walls - have an air gap between 2 walls which reduce amount of energy transfer by conduction

• Cavity wall insulation - cavity wall are which are filled with foam to reduce energy transfer by convection

• Double glazed windows - have an air gap between between 2 sheets of glass which prevent energy transfer by conduction

• Draught excluders - reduce energy transfers by convection

Explain how to investigate the effectiveness of materials as thermal conductors (6)

1. Boil water and put it into a beaker and measure the mass of the water using a top pan balance

2. Use a thermometer to measure the initial temperature of the water

3. Put a lid on the beaker and leave it for 5 minutes then measure the temperature of the water

4. Pour away the water and allow the beaker to cool

5. Repeat this again but with the beaker wrapped in different materials, make sure to use the same mass of water + same initial temperature

6. The lower the temperature difference the better the material is as an insulator

What is energy efficiency?

When more energy is transferred to a useful energy store then dissipated

What are the 3 ways in which energy can be more efficient?

• Lubrication

• Insulation

• Streamlined

What is the equation for efficiency in terms of energy transfer?

Efficiency = useful output energy transfer/total input energy transfer

What is the equation for efficiency in terms of power?

Efficiency = useful power output/total power input

What 2 things can efficiency be calculated as?

• Decimal (efficiency is always less than 1 because nothing is 100% efficient)

• Percentage (efficiency is always less than 100% because nothing is 100% efficient)

What one device is 100% efficient?

Electrical heaters

What are the 2 types of energy sources?

• Non-renewable energy sources

• Renewable energy sources

What is the difference between non-renewable and renewable energy sources?

Non-renewable energy sources will run out one day whereas renewable energy sources won’t

What are the 2 types of non-renewable energy sources?

• Fossil fuel

• Nuclear fuel

Give 3 examples of fossil fuels

• Oil

• Coal

• Gas (Natural)

What are the properties of non-renewable energy sources? (3)

• Reliable (produce a lot of energy)

• Will run out one day

• Harmful to the environment

What does burning coal and oil release + what does this lead to + what are the effects?

• Burning coal and oil releases sulfur dioxide which leads to acid raid

• Acid rain is harmful to trees and buildings

What is a big risk with oil production + what does this effect?

Oil spillages which cause harm to the sea and those at sea (animals)

What are the pros + cons for nuclear power? (5)

• Nuclear power is clean

• Does not cause pollution when generating electricity

• Is extremely reliable

• Decommissioning a run down power plant is expensive + takes years

• Nuclear power produces nuclear waste which is very dangerous (radioactive material) + radioactive waste is difficult to dispose of (stored for thousands of years before it is safe)

What do nuclear power plants run on?

Uranium and plutonium

Give 7 examples of renewable energy sources

• Solar

• Wind

• Water waves

• Hydro-electricity

• Bio-fuel

• Tides

• Geothermal

What are the pros + cons of renewable energy sources? (3)

• They will never run out

• Most of them do damage to the environment but less than non-renewable energy

• They are unreliable (don’t produce as much energy)

What are the 3 primary uses of energy sources?

• Transport

• Heating

• Generating electricity

What non-renewable energy sources are used in transport + for what? (2)

• Petrol + diesel are used for cars and are created from oil

• Coal is used in some old-fashioned steam trains to boil water and produce steam

What renewable energy sources are used in transport + for what?

Some vehicles use biofuel or a mix of biofuel and petrol or diesel

What non-renewable energy sources are used in heating + for what? (3)

• Natural gas is used to heat water which is then pumped into radiators in homes

• Coal is burnt in fireplaces

• Electric heaters used non-renewable sources to function

What renewable energy sources are used in heating + for what? (3)

• A geothermal heat pump uses geothermal energy resources to heat buildings

• Solar water heaters which use solar energy to heat water which heats water which is then used into radiators

• Burning bio-fuel can be used as heating

How does wind power generated electricity?

Via wind turbines which have generators that rotate to produce electricity

What are the pros + cons of wind energy? (7)

• There is no pollution

• Not reliable (rely on wind + some days there isn’t wind)

• Ruin the view

• Noisy

• No fuel costs + minimal running costs

• Don’t cause permanent damage

• Doesn’t produce an immediate response for high demand

How does solar power generate electricity?

By using the energy released from the sun in the form of solar panels

What are the pros + cons of solar energy? (5)

• Located in remote areas

• No pollution

• Not reliable (rely on sun + at night are useless)

• No running costs and free to maintain

• Doesn’t produce an immediate response for high demand

How does geothermal power generate electricity?

By using heat from the earth

What are the pros + cons of geothermal energy? (4)

• Reliable

• Does very little damage to the earth

• Aren’t many suitable locations for power plants

• Cost of building power plants is really high (compared to the energy it produces)

How does hydro-electricity power generate electricity?

Flooding of a valley by building a big dam

What are the pros + cons of hydro-electrical energy? (6)

• There is no pollution

• Habitats are destroyed when dams are built + valleys are flooded

• Produces an immediate response for high demand

• Not reliable (needs a country with a lot of lakes and no droughts)

• There are no fuel costs and minimal running costs

How does wave power generate electricity?

Wave powered turbines generate electricity using a generator

What are the pros + cons of wave energy? (6)

• There is no pollution

• Disturbs the sea bed and the habitats of sea animals

• Spoil the view

• Are a hazard to boats

• Not reliable (rely on waves + when there is no wind for waves are useless)

• No fuel costs and minimal running costs

How does tidal power generate electricity?

Through tidal barrages which are big dams built across rivers, with turbines in them

How are tides formed + how many times a day?

Are produced twice a day via the gravitational pull of the sun and the moon

What are the pros + cons of tidal energy? (6)

• No pollution

• Reliable

• Prevent boats from crossing bodies of water

• Spoil the view

• Disturb wildlife

• No fuel costs and minimal running costs

How do bio-fuels generate electricity?

Made from plant products or animal waste and are burnt to produce electricity

What are the pros + cons of bio-fuel energy? (6)

• Are carbon neutral (when burnt produce CO2 but the plants that are being burnt used CO2)

• Reliable

• Doesn’t produce an immediate response to high demand

• Can be stored

• Expensive to produce

• Large area of forest is removed to make space for it + this leads to increased CO2 + methane emissions

Why are fossil fuels bad?

Produce greenhouse gases which lead to global warming

What are the 3 reasons people wanted to use renewable energy resources?

• Fossil fuels are damaging to the environment

• Non-renewables will run out and we need to learn how to survive without them before they do

• Pressure from other countries led to the gov to set targets

How have car companies contributed to a more greener environment?

By producing electric cars that don’t need fossil fuels to run