P1 - Energy

Conduction primarily takes place in:

solids

Convection takes place in:

fluids (liquids and gases)

Name the 8 energy stores

Thermal, kinetic, gravitational potential, elastic, chemical, magnetic, electrostatic, nuclear

What can happen in an open system

The matter of the system can be exchanged with the outside world

What happens to energy in a closed system

there is no net change to the total energy, but it can be transferred between stores within the system

Define work done

Energy transferred

What are the two types of work done?

Mechanical and electrical

Kinetic energy lost =

gravitational potential energy gained

As an object falls, gravitational potential energy is converted into...

kinetic energy

Define system

The collection of matter in an object or a group of objects

Define internal energy

The total energy stored by the particles making up a substance or system; the sum of kinetic and potential energies

Define efficiency

the proportion of the energy supplied/input energy that is transferred into useful output energy

Efficiency=

useful energy output / total energy input

Define specific heat capacity

it is the amount of energy needed to raise the temperature of 1 kg of a substance by 1 degrees celsius

What way are buildings designed to prevent unnecessary heat loss by convection?

Sealed close doors and windows

What ways are buildings designed to prevent unnecessary heat loss by conduction (and convection)?

Cavity walls (filled with foam) and double glazing

How do cavity walls reduce heat loss from a building?

They are two walls placed together with an air gap between them to reduce energy transfer by conduction as conduction cannot happen in air. But convection can happen in gas, so foam is placed in the gap to prevent energy loss by convection.

Define power

The rate at which energy is transferred or work is done

Change in internal energy=

specific heat capacity x mass x change in temperature

Name some fossil fuels

coal, oil, natural gas

What is the main energy transfer for an apple falling from a tree?

Gravitational potential energy → kinetic energy

What is the main energy transfer for a long-distance runner?

Chemical energy → kinetic energy

How might a toy car be made more efficient?

Add oil to the moving parts as a lubricant

True or false: Warm fluids rise because they are less dense than cooler fluids

True

What are the pros of wind and solar energy?

Low running costs, no CO2 produced

What are the cons of wind and solar energy?

High upfront cost, weather dependant, takes up lots of space

What change of energy stores occurs when a wind turbine turns its generator?

Kinetic energy to electrical energy

What is solar energy most commonly used for?

Low energy devices like watches and calculators

What does geothermal energy naturally heat?

Hot springs

What is geothermal energy?

Thermal energy generated and stored in the earth's crust from radioactive decay

What are the advantages of hydroelectric energy?

Non polluting, low running cost, reliable supply

What are the disadvantages of hydroelectric energy?

Expensive initial set up, impacts surrounding environment, affects fish migration, stops boats

Define radiation in terms of heat energy transfer

When heat energy is transferred without particles

Define conduction in terms of heat energy transfer

When heat energy is transferred through collisions between neighbouring vibrating particles

Define convection in terms of heat energy transfer

When heat energy is transferred by particles moving position

What is the convection current?

the flow that transfers heat within a fluid

What are biofuels?

A fuel made from recently living organisms

What is the difference between biofuels and fossil fuels?

Biofuels are made of recently living organisms but fossil fuels are made of long dead matter

What are the pros of using nuclear energy?

No pollutants, unlikely isotopes will run out, all conditions

What are the pros of using biofuels?

renewable, cheap, easy transport

What are the pros of using hydroelectric dams?

no pollutants, reliable

What are the cons of using nuclear energy?

finite, produces radioactive waste, chance of disaster

What are the cons of using biofuels?

destruction of natural land, high energy to produce

When we say heat energy is transferred by 'radiation', we are referring to:

infrared radiation

What can IR radiation travel through?

A vacuum