OCR 21st Century Science A P1 P2 P3 Revision Notes

This is a word document containing notes given to me by a friend. They were quite useful for my revision in year 10 as they contain things which are relevant to the course.

They can also be used as flashcards if they are printed out.

Hope you find them helpful :)

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  • Created by: hajtastic
  • Created on: 14-02-14 16:28
Preview of OCR 21st Century Science A P1 P2 P3 Revision Notes

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Science P1,2,3
Physics 1: The Earth in the Universe
Unit 1.1: Our solar system and the stars
Centre of our universe = Sun!
Every planet has a/many moons which orbits it.
Asteroids: Irregular lumps of rock.
Comets: Small objects made of ice and rock, with long orbits around the sum.
Dwarf planets: Small lumps of rocks which orbit the sun.
Nearly 99% of the solar system's mass is the sun.
Jupiter: Heaviest planet
Neptune: Largest orbit
The sun is one of thousands of million stars in the Milky Way.
The Milky Way is one of thousands of millions of galaxies which make up the universe.
Light year: Distance which light travels in, in a year.
Light travels at 300.000 km/s.
Light takes a very long time to reach us from the stars.
All evidence on distant stars and galaxies come from radiation.
Real brightness: Appear as bright as each other.
Relative brightness: A star which is actually further away.
Observations of stars may be hard at night because of dust, rain, clouds and light pollution.
Parallax: When nearby stars move slightly against the fixed background of distant stars.
Unit 1.2:The fate of the stars
Nuclear fusion: Hydrogen nuclei jammed together so hard they combine to form helium and release energy.
Fusion in stars do this with other elements which spread through space when that stars' life ends.
Nuclear fusion only happens when there are very high densities and temps.
Heavy stars end their lives as supernovas.
Supernova: Massive explosion where different chemicals are made.
Solar system made from a collapsing cloud of dust and gas about 5000 million years ago.

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Apart from hydrogen, all the elements came from an explosion.
Galaxies appear to be moving away Redshift.
Redshift increases distance with Earth.
Universe started expanding approximately 14,000 million years ago.
Sun = 5000 million years ago
Earth = 4500 million years ago
Scientists believe in the Big Bang theory.
Detection of cosmic background radiation provide evidence to support the Big Bang theory.
Ultimate fate of Universe depends on how it continues to expand.…read more

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Seafloor spreading:
The seafloor between continents move apart by a few metres each year
Oceanic ridges: form on expanding seafloor where liquid rock from the mantle fill the gaps.
The Earth's magnetic field changes over the years.
Unit 1.4: Tectonic plates and seismic waves
Tectonic plates:
The Earth's crust has solid tectonic plates which float on semi liquid rocks.
Tectonic plates meet at a plate boundary where earthquakes, volcanoes & mountains are found.…read more

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You can only see when your eyes absorb electromagnetic radiation called light.
Some objects emit light, while other reflect light.
Black objects absorb most light.
Shiny objects reflect most light.
Electromagnetic spectrum:
All waves transmit through a vacuum at 300,000 km/s.
Electromagnetic waves transfer energy in packets called photons.
Energy in photons depend on the frequency of the waves the higher the frequency, the higher the amount
of energy in photons.…read more

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You can increase the thermal energy transferred by increasing its exposure time and intensity.
Water molecules are good at transferring energy in microwaves to thermal energy.
Cells contain water so will heat up when they absorb microwaves.
Microwaves reflect off the metal in the walls and door or are absorbed by them instead of escaping
protecting people from the radiation.
Mobile phone networks use low intensity microwaves.…read more

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The small amount of carbon dioxide has an effect
Methane is a strong absorber of infrared radiation, but there is very little of it.
Scientists use computer models to predict the effects of global warming. The models are tested by seeing if
they can use past data to predict today's climate.
Models suggest that global warming will result in more extreme weather events because of:
increased water vapour in the hotter atmosphere
increased convection in the atmosphere increasing wind speed.
Unit 1.…read more

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Wind, waves and sunlight
Primary energy sources can transfer their energy to secondary energy sources, e.g. electricity.
The burning of fossil fuels is increasing the amount of carbon dioxide in the atmosphere.
The greenhouse effect is causing global warming, an increase in the temperature of the Earth's surface.
Global warming is likely to result in climate change.
Power is the amount of energy transferred in one second, i.e. the rate of energy transfer.…read more

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Power stations use primary fuels, such as fossil, nuclear and biofuels, to boil water into steam.
2. The steam passes through a turbine, making its shaft spin round. The turbine shaft spins the magnet
3. Increasing the current drawn from the coil requires an increase in the rate of transfer of energy from
the primary fuel
Primary energy sources used to turn turbines directly include wind and water.
How power stations work:
1.…read more

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Electricity is convenient because it can transfer energy over long distances for many uses.
The National Grid is a network of cables which carries electricity throughout the UK.
Increasing the voltage of a power cable reduces the current. The National Grid carried electricity at a very
high voltage to reduce wasteful energy transfer in cables.
Substations connected to the National Grid reduce the voltage to 230 V for our homes.
Unit 1.…read more



Please do this for the rest of the science topics!!


Thank you so so so so much made my exam revision easier

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not really a fan

because I don't blow air


I found 1 error "Centre of our universe = Sun!" but other than that it's really good.


do you have any other revision documents such as these?




i meant is good 



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