c1 c2 c3 revision notes

21st century science

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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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Chemistry 2 : Material choices
Unit 1.1: Using and choosing materials
Each material has properties that make it suitable for the job is it doing:
Rubber is used for car tyres because it's hard and elastic
Fibres are used to weave cloth into clothes
Plastics keep their shape when moulded into objects like washingup bowls.
Properties describe how a material behaves.…read more

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Crude oil consists mainly of a mixture of hydrocarbons, which are chain molecules of varying lengths up to 100
carbon atoms long.
Unit 1.3: Separating crude oil
Crude oil is separated by fractional distillation:
The oil is heated up which turns it all into gases.
The distillation tower gets cooler as it gets higher
Gas molecules condense into liquids when they cool
Liquids with similar boiling points collect together, called fractions.
Hydrocarbons in each fraction have boiling points within a range of temperature.…read more

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Unit 1.5: Nanotechnology and nanoparticles
Nanoparticles are materials containing up to a thousand atoms.
occur naturally, such as salt in seaspray
occur by accident, such as solid particulates made when fuels burn
can be designed in laboratories
Nanotechnology is the use and control of very small structures, which are measured in nanometres (nm).
A nanometre is one millionth of a millimetre.
Some nanoparticles are effective catalysts as they have a large surface area. Increasing surface area provides
more sites for reactions to take place.…read more

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Risks of easting salt in foods:
High blood pressure
Prevents bacteria growth
Heart failure
This means salts is classified as a hazard.
A risk is the chance of getting ill, and the consequences if you did.
Risks can be estimated by measuring salt intake.
Unit 1.3: Reacting and making alkalis
Alkalis made indicators change colour.
Litmus paper turns blue in alkalis and red in acids.
Alkalis are used for:
dying cloth
neutralising acid soil
making soap
making glass.…read more

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Unit 1.5: Safe?
To decide the level of risk of a particular chemical we need to know:
how much of it is needed to cause harm
how much will be used
the chance of it escaping into the environment
who or what it may affect
A Life Cycle Assessment (LCA) measures the energy used to make, use and dispose of a substance, and its environmental
impact.…read more


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