Heat energy can be transferred by conduction, convection and radiation.
Dark, matt surfaces are better at absorbing heat and radiating heat than light shiny surfaces.
Light surfaces are better at reflecting heat.
Heat is emitted as infrared radiation. The hotter an object, the more infrared energy it radiates.
This is a type of electromagnetic radiation so it is waves.
This allows infrared to pass through a vacuum.
Kinetic theory
Particles in solids, liquid and gases have different amounts of energy. They are arranged differently as well.
Solids have particles close together which vibrate at a fixed position.
Liquids have particles close together but they move around each other.
Gases have particles far apart and they move quickly in random directions.
Solids have a fixed shape and cannot flow as the particles cannot move
They cannot be compressed as particles are close together and have no space to move into.
Liquids flow and take the shape of the container as they can move around each other
Liquids cannot be compressed as particles are close together and have no space to move.
Gases flows and fills the container they are put in as they can move around quickly in all directions.
They can be compressed as there are a lot of space between particles.
Conduction
Heat energy can be transferred through conduction.
Metals are good conductors but Non Metals and gases are usually insulators.
Heat energy is transferred from hot to cold.
When an object is heated, particles close to the flame get kinetic energy and vibrate more quickly.
They bump into other particles next to them and transfers the energy across. The energy is spread through the material.
In metals electrons are free to move around.
This allows them to pick up energy and collide with ions as the move throughout the structure which transfers the heat energy from one point to another.
Convection
Liquids and gases can transfer heat energy through convection.
Convection happens when a liquid or gas is heated they expand.
This is because the particles have more kinetic energy and move faster resulting in the particles taking up more volume as the gaps between particle increases.
The liquid or gas in hot areas are less dense than cold areas as they are expanded.
The denser cooler liquid or gas displaces the warm liquid or gas where it is heated by the source repeating the process.
Eventually the heat is transferred throughout the room.
Evaporation
This is when a liquid change to a gas as it is heated.
A liquid e.g. water, have particles with different energies, some of it will have enough energy to escape the liquid as a gas.
The gas leaves the liquid which brings heat energy away from the liquid. The particles left in the liquid have a lower average kinetic energy than before so the liquid cools
Condensation
Particles in a gas have different energies, some will not have enough energy to remain a gas, they will come closer together and form bonds between them releasing energy.
Condensation increase when temperature decreases
Evaporation increase when temperature increases
More surface area of the liquid and air flow also increase the rate of evaporation of a liquid
A bigger difference in temperature between the objects and the surroundings, the faster heat energy is transferred. Other factors include:
Surface area and volume
Material of object
Nature of the surface the object is touching
Animals are adapted to their surroundings
in hot climates, animals like mice have a large surface area to volume ratio.
They lose heat quickly so they don't over heat but they need to eat alot of food to replace the energy lost
Elephants have a small surface area to volume ratio, they lose heat slowly so they have problems with overheating.
Elephants have large ears to radiate heat to the surroundings.
Arctic fox has smaller ears to reduce surface area to volume ratios.
Engineering design
Car radiators are flat with many fins to provide a large surface area.
U-values
This measures the efficiency of a material as an insulator
Solar panels use heat from the sun to provide hot water or to heat up buildings.
Specific heat capacity calculates the energy required to heat up a substance.
A lower U value shows a better insulator
A high U value shows a better conductor.
Payback time
Payback time (years) = cost of installation / saving per hear
Solar panels
Solar panels heat up water but does not generate electricity.
They receive heat energy from the sun and transferred to cold water that is pumped up from a storage tank.
The water heats up and moves back into the storage tank.
Solar energy is renewable
No pollutant gas
They may produce very hot water in sunny climate. In cooler areas, a conventional boiler may be needed.
Warm water cannot be produced at night,
Specific heat capacity
E = m * c * θ
Energy (J) = Mass(kg) * Specific heat capacity (J/kg) * Change in temperature (°C)
Heat transfer and efficiency
There are 10 types of energies
Magnetic
Kinetic
Heat
Nuclear
Light
Gravitational
Chemical
Sound
Electrical
Elastic
Energy can be converted from one form to another but they cannot be created or destroyed.
Energy can be transferred usefully, store or dissipated as heat energy
Efficiency
Efficiency = (useful energy out / total energy in) x 100
Electrical appliances energy calculations
E= P*t
Energy (kWh) = Power (kW) x Time (h)
Energy (J) = Power (W) x Time (s)
Cost
Total cost = power (kWh) * time (h) * cost per unit
Generating Electricity
Electricity is convenient as we can change it into many different energies.
We generate it using non-renewable and renewable sources.
There are advantages and disadvantages of both
Fossil Fuels
Coal, Oil and Natural gas
Formed from remains of living organisms millions of years ago. They are non-renewable
Fossil fuel is a store of chemical energy
When they are burned they are transferred as heat.
Which heats up water and becomes steam which rises
The heat is transferred into kinetic energy.
The steam drives turbines which turns a generator and the energy is transferred into electrical energy.
Advantages
Reliable, 3/4 of power stations are fueled by fossil fuel.
Disadvantage
Non-renewable- supply is limited and will run out.
Release of sulfur dioxide which causes acid rain
Carbon dioxide is released. They are a green house gas therefore contribute to global warming.
Coal releases the most pollution and natural gas releases the least for a given amount of energy released.
Carbon capture
We can store carbon dioxide in old oilfields or gas fields under the North Sea.
Nuclear fuels
Nuclear fuel are mainly uranium or plutonium which are radioactive metals.
They go through nuclear fissions which release a vast amount of heat energy.
The heat energy is used to boil water which turns to steam.
The steam is used to spin turbines which drives generators to produce electricity.
Advantages
They don't release carbon dioxide and sulfur dioxide. Reliable
Disadvantages
Non-renewable source, limited supply and will run out.
Radioactive waste which can be hazardous for thousands of years and needs to be stored safely.
There is a chance of an accident which can lead to large amounts of radioactive material to be released into the environment e.g. chernobyl disaster
Wind Energy
Convection currents in the Earth's Atmosphere driven by heat energy from the sun.
Kinetic energy in wind is renewable
Wind drives the blades of a wind turbines to spin, they have gears that link to a generator.
Wind Farms can be formed by several wind farms grouped together.
Advantage
renewable energy- unlimited supply
No harmful polluting gas produced
no fuel cost
Disadvantages
Not reliable- there are days without wind.
Noise and sight pollution
Expensive
Water
Wave
Wave machines use kinetic energy of waves as they rise and fall to drive electricity
Tides
Water move in and out of river mouths because of tides
A tidal barrage built over a river estuary uses the kinetic energy of the moving water.
They drive generators as they rush through tubes in the barrage.
Hydroelectric
Dams can be built to generate electricity across a river valley.
Area behind the dam is flooded and water is used to drive generators as they rush down tubes in the dam to the otherside.
The water contain gravitational potential energy which transfers to kinetic energy as they fall.
Advantages
Renewable energy
No fuel cost
No pollutant gas
Dams and tidal barrages are reliable.
Disadvantages
Expensive
Wave machines are difficult to scale up to produce large amounts of energy
Tidal barrages destroys habitats of organisms
Dams flood farmlands and people are forced to leave their homes.
Rotting vegetation under the water release methane which is a greenhouse gas.
Geothermal energy
Some rocks in the crust contain radioactive substances such as uranium.
The radioactive decay of these releases heat energy.
In volcanic areas, the rock may heat water so it rises naturally and drives turbines to generate electricity.
Sometimes we have to pump water down so they can be heated by the hot rocks so that steam can rise up as steam at a different location.
Advantages
Renewable source
Reliable
No fuel cost
No harmful pollutant gas
Disadvantages
Not all areas of the world are suitable for this type of method.
Solar Energy
Solar cells convert light into electrical energy.
These are different from solar panels.
Advantages
Renewable
No fuel cost
No harmful pollutant gas
Can provide electricity in remote locations
Disadvantages
Expensive and unreliable + inefficient
Do not work at night
Power Stations
Different power stations have different start up time
Start up time for power stations are as follows starting from the shortest
Gas
Oil
Coal
Nuclear
The bottom ones are used to provide base load electricity.
The shorter ones provide extra electricity at peak times.
It is expensive to dismantle old nuclear power stations.
Waves
Vibrations that transfer energy from one place to another without transferring the medium along with it.
Waves that need a medium are sound waves, seismic and water waves.
Waves that do not are electromagnetic radiation which can travel through a vacuum.
Transverse
Oscillations are at right angles (perpendicular) to the direction of the travel
Electromagnetic radiation are examples of this.
Water and Secondary seismic waves are also this.
Longitudinal
Oscillations are at the same direction as the direction of the energy transfer.
Sound waves, Primary seismic waves and water waves are this.
Compressions and rarefactions
Compressions are where particles move closer together
rarefactions are where particles move away
Amplitude
The distance from the highest or lowest point in waves to the undisturbed position.
Wave length
Length from one wave to another at the same point. Crest to crest/ trough to trough.
Measured in Metres (m)
Frequency
Number of waves produced per second. Also the number of waves that pass through a point a second.
Measured in Hertz (Hz)
v = f × λSpeed (m/s) = Frequency (Hz) * Wavelength (m)
Refraction
Sound waves and light rays change speed when they pass a boundary between two substances with different densities e.g. glass and air.This causes them to change direction.This doesn't happen for waves if they hit the boundary at 90 degrees. They will carry straight on without changing directions.
Diffraction
When waves meet a gap in a barrier and they spread out.
The spread is affected by how wide the gap is compared to the wavelength of the wave
Significant diffraction only happens if the gap size is around the same as the wavelength of the wave.
Reflection
When sound and light waves reflect from surfaces.
They obey the law of reflection
The angle of incidence is equals the angle of reflection
The normal is a line drawn perpendicular to the reflector
The angle of incidence is the angle from the normal to the light ray going to the reflector
The angle of reflection is the angle between the reflected ray to the normal.
Images appears from a point behind the mirror. They are virtual, upright, and laterally inverted.
Ray diagram
Sound
They can travel through solid liquids and gases.
Amplitude show how loud the sound is
the frequency shows what the pitch is.
A range of human hearing is 20 Hz to 20,000 Hz
Electromagnetic radiation
Light can be split up using a prism to form a spectrum of colours.
There are other types of electromagnetic radiation with different wavelengths
from lowest wave length to highest :
Radio waves used in TV signals and radios
Microwaves used in mobile phones and TVs
Infrared used in optical fibre communication
Light used in seeing
Ultraviolet used to detect forged bank notes
X rays used in medical images of bones
Gamma rays used to kill bacteria and cells.
Radio waves are able to diffract at gaps between hills so they can be received behind hills.
They don't need a repeater for people to receive the signals.
Microwaves do as they cannot diffract and requires a line of sight. Repeaters broadcast the signal again so it travels further.
Microwaves used for mobile communications are not harmful as they are too weak to damage tissues by heating and they are not ionising Microwaves can pass through the ionosphere so they can be used to communicate with satellites
Radio waves can also be reflected from the ionosphere which is an electrically charged layer in the upper atmosphere.
They can receive signals even when not in sight of the transmitter as the earth's surface curves.
Visible light lets us see, books, videos and light signals are examples of how we communicate with light. Visible light need transmitters and receivers to be in a line of sight.
Infrared can be used to heat up food but also used to communicate through optical fibres.
The Big Bang Theory
This theory states that all matter was once concentrated at one single point which exploded and began to expand rapidly. It is still expanding today. The universe is around 13.7 billion years old.
CMBR Cosmic Microwave Background Radiation can be detected in space, this is radiation which is left from the Big Bang.
The Doppler effect
When a source of waves is moving towards you, the wavelength decreases and the frequency increases
This makes sound waves higher pitched.
When a source of waves moves away from you, the wavelength increases and the frequency decreases so sound waves are lower pitched.
Red shift
We inspect our sun which contains helium and we know the spectrum of light from the sun where helium has absorbed light.
When we look at distant stars in other galaxies we see the same pattern but shifted to the red side of the spectrum with wavelengths increased and frequencies decreased.
This means that because of the doppler effect, galaxies are proven to be moving away from us.
With galaxies further away, the red shift is increased.
This suggest that the universe is expanding and everything is moving away from everything else
CMBR
Microwaves comes from every direction in space.
It comes from radiation created at the beginning of the universe.
The Big Bang theory is the only that explains why CMBR exists.
Vibrations that transfer energy from one place to another without transferring the medium along with it.
Waves that need a medium are sound waves, seismic and water waves.
Waves that do not are electromagnetic radiation which can travel through a vacuum.
Transverse
Oscillations are at right angles (perpendicular) to the direction of the travel
Electromagnetic radiation are examples of this.
Water and Secondary seismic waves are also this.
Longitudinal
Oscillations are at the same direction as the direction of the energy transfer.
Sound waves, Primary seismic waves and water waves are this.
Compressions and rarefactions
Compressions are where particles move closer together
rarefactions are where particles move away
Amplitude
The distance from the highest or lowest point in waves to the undisturbed position.
Wave length
Length from one wave to another at the same point. Crest to crest/ trough to trough.
Measured in Metres (m)
Frequency
Number of waves produced per second. Also the number of waves that pass through a point a second.
Measured in Hertz (Hz)
v = f × λSpeed (m/s) = Frequency (Hz) * Wavelength (m)
Refraction
Sound waves and light rays change speed when they pass a boundary between two substances with different densities e.g. glass and air.This causes them to change direction.This doesn't happen for waves if they hit the boundary at 90 degrees. They will carry straight on without changing directions.
Diffraction
When waves meet a gap in a barrier and they spread out.
The spread is affected by how wide the gap is compared to the wavelength of the wave
Significant diffraction only happens if the gap size is around the same as the wavelength of the wave.
Reflection
When sound and light waves reflect from surfaces.
They obey the law of reflection
The angle of incidence is equals the angle of reflection
The normal is a line drawn perpendicular to the reflector
The angle of incidence is the angle from the normal to the light ray going to the reflector
The angle of reflection is the angle between the reflected ray to the normal.
Images appears from a point behind the mirror. They are virtual, upright, and laterally inverted.
Ray diagram
Sound
They can travel through solid liquids and gases.
Amplitude show how loud the sound is
the frequency shows what the pitch is.
A range of human hearing is 20 Hz to 20,000 Hz
Electromagnetic radiation
Light can be split up using a prism to form a spectrum of colours.
There are other types of electromagnetic radiation with different wavelengths
from lowest wave length to highest :
Radio waves used in TV signals and radios
Microwaves used in mobile phones and TVs
Infrared used in optical fibre communication
Light used in seeing
Ultraviolet used to detect forged bank notes
X rays used in medical images of bones
Gamma rays used to kill bacteria and cells.
Radio waves are able to diffract at gaps between hills so they can be received behind hills.
They don't need a repeater for people to receive the signals.
Microwaves do as they cannot diffract and requires a line of sight. Repeaters broadcast the signal again so it travels further.
Microwaves used for mobile communications are not harmful as they are too weak to damage tissues by heating and they are not ionising Microwaves can pass through the ionosphere so they can be used to communicate with satellites
Radio waves can also be reflected from the ionosphere which is an electrically charged layer in the upper atmosphere.
They can receive signals even when not in sight of the transmitter as the earth's surface curves.
Visible light lets us see, books, videos and light signals are examples of how we communicate with light. Visible light need transmitters and receivers to be in a line of sight.
Infrared can be used to heat up food but also used to communicate through optical fibres.
The Big Bang Theory
This theory states that all matter was once concentrated at one single point which exploded and began to expand rapidly. It is still expanding today. The universe is around 13.7 billion years old.
CMBR Cosmic Microwave Background Radiation can be detected in space, this is radiation which is left from the Big Bang.
The Doppler effect
When a source of waves is moving towards you, the wavelength decreases and the frequency increases
This makes sound waves higher pitched.
When a source of waves moves away from you, the wavelength increases and the frequency decreases so sound waves are lower pitched.
Red shift
We inspect our sun which contains helium and we know the spectrum of light from the sun where helium has absorbed light.
When we look at distant stars in other galaxies we see the same pattern but shifted to the red side of the spectrum with wavelengths increased and frequencies decreased.
This means that because of the doppler effect, galaxies are proven to be moving away from us.
With galaxies further away, the red shift is increased.
This suggest that the universe is expanding and everything is moving away from everything else
CMBR
Microwaves comes from every direction in space.
It comes from radiation created at the beginning of the universe.
The Big Bang theory is the only that explains why CMBR exists.