GCSE AQA Chemistry 'Unit 1a' Revision Guide

Revision guide for the first half of the GCSE AQA Chemistry 'Unit 1' / 'C1' exam paper.

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GCSE Chemistry
`Unit 1a' written by Applequestria
Table of Contents
Table of Contents..................................................................................................................................... 1
Atoms ...................................................................................................................................................... 2
The periodic table .................................................................................................................................... 3
Chemical reactions................................................................................................................................... 3
Calcium carbonate ................................................................................................................................... 4
Calcium carbonate (continued) ................................................................................................................ 5
Extracting metals ..................................................................................................................................... 6
Extracting metals (continued) .................................................................................................................. 7
Properties and uses of metals .................................................................................................................. 8
Alloys ....................................................................................................................................................... 8
Crude oil .................................................................................................................................................. 9
Hydrocarbons .......................................................................................................................................... 9
Hydrocarbon fuels.................................................................................................................................. 10
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Atoms
All substances are made of atoms. A substance that is made of only one sort of atom is called an
element. There are about one hundred different known elements. Elements are shown in the periodic
table. The groups contain elements with similar properties. Atoms of each element are represented
by a chemical symbol (for example, O represents an atom of oxygen and Na represents an atom of
sodium).…read more

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The periodic table
Elements in the same group in the periodic table have the same number of electrons in their highest
energy level (outer electrons) and this gives them similar chemical properties.
For example, the alkali metals of group one all have one electron in their highest energy
levels. This makes them very reactive. They all react with water to form alkali metal
hydroxides, which dissolve in water to form an alkaline solution, and hydrogen gas.…read more

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Calcium carbonate
Limestone, mainly composed of the compound calcium carbonate (CaCO3), is quarried and can be
used as building material. For example, old buildings such as cathedrals are often made from
limestone blocks.
Limestone is mainly composed of the compound calcium carbonate (CaCO3).
Calcium carbonate thermally decomposes on heating to produce calcium oxide and carbon
dioxide. The carbonates of magnesium, copper, zinc and sodium thermally decompose on
heating in a similar way.…read more

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Calcium carbonate (continued)
There are issues with quarrying limestone:
Quarrying damages the landscape.
Quarrying produces noise.
Quarrying produces dust.
Destroys habitat.
Transporting produces noise.
Transporting produces pollution.
Waste produce unsightly tips.
There are issues with using limestone:
Cement factories use a lot of energy to produce cement and quicklime. The energy comes
from burning fossil fuels, which causes pollution.
Cement factories produce a lot of dust, which causes breathing problems.
There are advantages with using limestone:
Limestone is used to make houses and roads.…read more

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Extracting metals
Ores contain enough metal to make it economical to extract the metal (and is usually a metal oxide).
Ores are mined and may be concentrated before the metal is extracted and purified. The economics
of extraction may change over time:
If market price rises, it might be worth extracting more.
If market price drops, it might not be worth extracting more.
As technology improves, it might be worth extracting more.…read more

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Extracting metals (continued)
Metals less reactive than carbon are extracted by reduction:
Copper is extracted by reduction. This is done by reduction of copper(II) oxide ore in a
furnace and this is called smelting. Disadvantage is that impure copper is produced.
Copper is purified by electrolysis. This is done by electrolysis of copper(II) sulphate solution.
Advantage is that pure copper is produced. Disadvantage is that a lot of energy is used.
Electrolysis is the breaking down of an ionic compound by electricity.…read more

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Properties and uses of metals
The elements in the central block of the periodic table are known as transition metals. Like other
metals they are good conductors of heat and electricity and can be bent or hammered into shape.
They are useful as structural materials and for making things that must allow heat or electricity to
pass through them easily. However, metals can corrode when exposed to air and water and can this
can cause loss of strength and hardness.…read more

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Crude oil
Crude oil is a mixture of a very large number of compounds. A mixture consists of two or more
elements or compounds not chemically combined together. All elements or compounds in a mixture
keep their properties. All elements or compounds in a mixture can be separated using physical
methods.
Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon
atoms only known as hydrocarbons. Crude oil consists of hydrocarbons not chemically
combined together.…read more

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Hydrocarbon fuels
Crude oil fractions are used to generate electricity because:
Many devices use crude oil fractions.
They are easy to use.
They are cheap to use.
They are readily available.
New technology is being discovered.
New oil reserves are being discovered.
Crude oil fractions should not be used to generate electricity because:
They are a non-renewable energy source.
Some think we should conserve crude oil for chemical and medicines and use alternative
energy sources instead.…read more

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