OCR 21st Century Science A C1 C2 C3 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 16:25
Preview of OCR 21st Century Science A C1 C2 C3 Revision Notes

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Science C1,2,3
Chemistry 1: Air Quality
Unit 1.1: The changing air around us (Pg. 23)
Air composition: (Dry air)
78% : Nitrogen
21% : Oxygen
1% : Argon and small volumes of other gases
Clouds are made up of water or ice.
Dust are made up of solids, they are not part of the air.
Oxygen reacts with most metals to make solids metal oxides.
To find out percentage of oxygen in the air we can pass air over heated copper.
The Earth's atmosphere was approximately found 4 billion years ago, by the gases given out by volcanoes
Carbon Dioxide, Water Vapour, Lava, Dust.
1. 4 billion years ago the Earth's atmosphere was very hot. As the Earth cooled down, oceans formed
from the condensed water.
2. About 1 billion years after, simple bacterialike creatures evolved to use photosynthesis. This
removed carbon dioxide from air, and released oxygen, allowing organisms to evolve.
3. Carbon dioxide was removed by plants and animals dying and becoming buried. Over millions of
years some of the buried material became fossil fuels.
4. Carbon dioxide dissolved in oceans reacts with salts to form insoluble calcium carbonate. This forms
sediments which become buried and cemented to form sedimentary rocks.
Ideas of the composition of the Earth's atmosphere have changed over time:
Sixty years ago many scientists thought the early atmosphere was largely ammonia and methane.
Recent rock composition discoveries showed early ideas were not correct, and the early atmosphere
was largely carbon dioxide.
Unit 1.2: Humans, air quality and health
Pollutants are gases that are harmful to our health, E.g: Carbon monoxide, Nitrogen oxides & Sulphur dioxide.
Pollutants are harmful to the environment, people and animals living there.
Sulphur dioxide and Nitrogen dioxide cause acid rain.
Carbon dioxide is linked to climate change.
Human activity is increasing the gas levels in the atmosphere
Carbon Dioxide is measure in parts per million (PPM).
Carbon Monoxide, Nitrogen Oxides & Sulphur dioxide are measure in parts per billion (PPB).
The amount of gases are measured by air quality monitors ­ Data transmits to a computer for analysis.

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Correlation: Link between a factor and an outcome.
Unit 1.3: Burning fuels
Oxygen is needed for any fuel to burn and release energy.
Hydrocarbons = Fossil fuels.
Only contain carbon & hydrogen.
When hydrocarbons burn:
Hydrocarbon fuel + Oxygen Carbon dioxide + Water (+ Energy)
Oxidation: When oxygen is added to a substance
Reduction: When oxygen is removed from a substance
Combustion: An oxidation reaction. (Burning)
Atoms do not change! They get rearranged.
Molecules: When atoms of nonmetal elements join.…read more

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Dissolves in rain water/oceans (CO2)
Mean = A good estimate of true value
Range = Difference between high and low result
Removing outliers could lead to mistakes.
Unit 1.…read more

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Stiffness is the force needed to bend a material
Hardness is how well a material stands up to wear. Compared by scratching two materials together
Density is the mass of a given volume of material. Compares how heavy something is for its size.
Density is mass per unit volume. (g/cm^3)
Unit 1.2: Natural and synthetic materials
All the materials we use are chemicals or mixtures of chemicals.
Metals are chemicals which are shiny, malleable and electrical conductors.
Ceramics include clay, glass and cement.…read more

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A polymer is made by a process called polymerisation.
Ethene is a monomer used to make polyethene.
Material choice will depend on comparing properties for different jobs, with cost being a factor.
Unit 1.4: Polymers: properties and improvements
Small forces attract molecules to each other.
The forces are strongest when the molecule are close together.
The properties of polymers depend upon how their molecules are arranged and held together.
Low density polyethene (LDPE), E.g: plastic carrier bags, has long molecules with branches.…read more

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µm = 1 x 10^6m
1,000,000,000 nanometres = 1m so, 1nm = 1 x 10^9m
Unit 1.6: The use and safety of nanoparticles
Silver nanoparticles are very good at killing bacteria. They can be added to fibres and woven into socks, put into wound
dressings, put into plastic and made into food containers.
Titanium oxide nanoparticles are put into sunscreen. They make the sunscreen transparent and absorb UV light.
Nanoparticles can be mixed with other materials like metals, ceramics and plastics, called composites.…read more

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Limestone formed while Britain was covered in sea:
Shellfish died forming sediments on the sea bed.
Sediments compacted and hardened to form limestone, a sedimentary rock.
Tectonic plate movements pushed the rock to the surface
Gradually the rocks above were eroded away until the limestone was exposed.
Coal formed in wet swampy conditions when plants like trees and ferns died and became buried. This excluded oxygen,
slowly down the decay.…read more

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Alkalis = Greater than 7, Blue or Violet pH colour
They are soluble metal hydroxides or carbonates.
Metal hydroxide/carbonates are normally insoluble bases.
Hydroxide + Acid Salt + Water
Carbonates + Acid Salt + Water + Carbon dioxide
Unit 1.4: Electrolysis
Electrolysis breaks up compounds using electricity.
The electrolysis of brine makes:
Chlorine gas
Hydrogen gas
Sodium hydroxide
Anode ­ Positive electrode
Cathode Negative electrode
During brine electrolysis, chlorine forms at the anode and hydrogen at the cathode.…read more





These are great!! :D


These are so helpful, I have my exams soon and this is a life saver!

Pete Langley - Get Revising founder

Excellent notes




Omg, this is a life saver since I have my GSCHE's in the next 2 weeks!

Harmen Gill

mine is tomorrow




this was great help !!!!! is there one for p1 p2 p3 ?

Nana K

Lifesaver thank youuuu!


omg amazin




Great notes. Didn't even look at them.





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