Energy Changes And Energy Stores + Conservation And Dissipation Of Energy + National and global energy resources

What is a system?

An object or group of objects.

Why is it that energy can never be used up, created or destroyed?

It is simply transferred between different energy stores and objects.

What are the energy stores?

1. Thermal

2. Kinetic

3. Gravitational Potential

4. Elastic Potential

5. Chemical

6. Magnetic

7. Electrostatic

8. Nuclear

How can energy be transferred?

1. Mecanically (by a force doing work)

2. Electrically (work done by moving charges)

3. By Heating

4. By Radiation (e.g. light or sound)

What happens when a system changes?

Energy is transferred.

What is a closed system?

Systems where neither matter nor energy can leave.

What type of energy is stored in moving objects?

Kinetic energy.

What does the energy in the kinetic energy store depend on?

The mass and the speed of the object.

What is the equation for kinetic energy?

½ × mass (kg) × (speed)²

What is speed measured in?

Miles per second (m/s)

What type of energy is stored in stretched objects?

Elastic potential energy.

What is the equation for elastic potential energy?

½ × spring constant × (extension)²

What is spring constant measured in?

Newtons per metre (N/m)

What is extension measured in?

Metres (m)

What type of energy is stored in raised and falling objects?

Gravitantial potential energy.

What is the equation for gravitational potential energy?

mass × gravitational field strength × height

What is specific heat capacity?

The amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.

What is the equation for specific heat capacity?

Change in thermal energy (J) = Mass (kg) x Specific heat capacity x temperature change

What is the rearranged equation for specific heat capacity?

Specific heat capacity = Change in thermal energy ÷ (Mass x Temperature Change)

What is power?

The rate at which energy is transferred or the rate at which work is done.

What is the equation for power?

power = energy transferred/work done ÷ time

What is the conservation of energy principle?

Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.

What are the two ways of reducing unwanted energy transfers?

Through lubrication and thermal insulation.

How does lubrication reduce unwanted energy transfers?

It reduces friction between the surfaces of object when they move.

How does thermal insulation reduce unwanted energy transfers?

Reducing the amount of energy lost to the surroundings.

What are cavity walls?

Walla made up of an inner and outer wall with an air gap in the middle; reduces energy loss by conduction in the walls.

How does cavity wall insulation work?

The gap in the cavity wall is filled a foam, which also reduces energy loss by convection in the wall cavity.

How do double glazed windows work?

The same way as cavity walls - an air gap between the two sheets of glass prevent energy transfer by conduction through the windows.

How can the efficiency of an intended energy transfer be increased?

By insulating objects, lubricating them or making them more streamlined.

How is heat transferred in solids?

Conduction.

How is heat transferred in fluids?

Convection.

How does heat travel through empty space?

In a form of radiation.

What is conduction?

When vibrating particles transfer energy to neighbouring particles so that the heat is spread out evenly.

Why does conduction mainy occur in solids?

The particles are held together really closely so there are lots of collisions.

What are the main energy resources available for use on Earth?

• Fossil fuels (coal, oil and (natural) gas)

• Nuclear fuel

• Bio-fuel

• Wind

• Hydroelectricity

• Geothermal

• The tides

• The Sun (Solar)

• Water waves

What is a renewable energy source?

One that is being (or can be) replenished as it is used.

What energy sources are non-renewable?

• Fossil fuels (coal, oil and (natural) gas)

• Nuclear fuel

What energy sources are renewable?

• Bio-fuel

• Wind

• Hydroelectricity

• Geothermal

• The tides

• The Sun (Solar)

• Water waves

What are the uses of energy resources?

Transport, electricity generation and heating.

How are non renewable energy sources used in transort?

• Perol/diesel powered vehicles (incl. most cars) use fuel created from oil.

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

How are renewable energy sources used in transport?

Vehicles that run on pure bio-fuels are renewable.

How are non renewable energy sources used in heating?

• Natural gas is the most widely used fuel for heating homes in the UK.

• The gas is used to heat water, which is then pumped into radiators throughout the home.

• Coal is commonly bunt in fireplaces.

• Electric heaters use electricity generated from non-renewable energy resources.

How are renewable energy sources used in heating?

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

• Solar water heaters work by using the sun to heat water which is then pumped into radiators in the building?

• Burning bio-fuel or using electricity generated from renewable resources can also be used for heating.

What are the pros of fossil fuels?

• They are relatively cheap

• Can be used in any conditions (e.g. don't require wind or sunshine to work)

• Much of our current infrastructure is designed to run using fossil fuels.

What are the cons of fossil fuels?

• They're a limited resource so will run out one day.

• They produce carbon dioxide when burned, which is a greenhouse gas and contributes to global warming

• They sometimes produce toxic gases when burned - such as sulfur dioxide (causes acid rain) and carbon monoxide

What is nuclear energy?

Energy obtained via nuclear reactions, such as nuclear fission reactions in nuclear power stations.

What are the prons of nuclear fuels?

• Nuclear fuels do not produce any pollutants like sulfur dioxide, or greenhouse gases like carbon dioxide

• Can be used in any conditions.

• Although nuclear fuel (like uranium) is a limited resource, it is very unlikely to run out for a very long time.

What are the cons of nuclear fuels?

• It is technically still a non renewable energy resource.

• Nuclear power stations produce radioactive waste, which remains harmful for thousands of years and so must be stored very carefully.

• It is quite expensive.

• If there is a problem at the power station, there is a very small chance of a nuclear meltdown which could release large amounts of radioactive material into the environment.

What is wind energy?

Power captured through the use of turbines.

Whar are the pros of wind energy?

• Low running costs.

• Does not produce harmful pollutants.

What are the cons of wind energy?

• The process of making it produces pollutants.

• High upfront costs

• Dependent on the weather.

• No way to increase supply in times of demand.

• Take up a lot of space

What is solar energy?

Energy generated by solar cells; often in the form of solar panels.

What are the pros of solar energy?

• Low running costs.

• Does not produce harmful pollutants.

What are the cons of solar energy?

• The process of making it produces pollutants.

• High upfront costs

• Dependent on the weather.

• No way to increase supply in times of demand.

• Take up a lot of space.

What is geothermal energy?

Energy generated and stores in the earths’s crust.

How does geothermal energy provide heating?

Through pumping water into the ground, allowing it to heat up then using it to heat up homes.

How does geothermal energy provide electricity?

The water is left underground for so long that it is converted to steam, the gaseous steam rises and turns turns turbines driving the generators to produce electricity.

What are the pros to geothermal energy?

• It only slightly damages the environment

• Running it doesn’t produce any pollutants.

What are the cons to geothermal energy?

• Can only be used in certain areas (e.g volcanic regions)

• The power plants can be expensive to build.

What are biofuels?

Fuels made from recently living organisms.

What are the pros of biofuels?

• They can be mixed with fossil fuels.

• They can be good substitute for fossil fuels.

What are the cons of biofuels?

• They need somewhere to grow all the plants required.

Why would someone argue that biofuels are not carbon neutral?

It is only carbon neutral if the plants are grown at the same rate they are burned.

What is the difference between hydroelectric dams and tidal barrages.

Hydroelectric dams trap water that comes from upstream while tidal barrages make use of the tides.

What are the pros of hydroelecric and tidal fuels?

• Produce large amounts of energy without pollution.

• Running costs are fairly low.

• Work on both large and small scales.

What are the cons of hydroelecric and tidal fuels?

• Often have abig impact on the surrounding environment.