AQA GCSE 2012 CHEMISTRY UNIT 1 REVISION NOTES

My chemistry notes for unit 1.. hope theyre useful!

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Atomic, elements and compounds.
All substances are made of Atoms.
Some substances are made up of only one type of atom, we call these Elements.
Most substances we come across aren't pure metal, but have different atoms joined together, we
call these Compounds. Chemical bonds hold the atoms tightly together.
An Atom is made up of a tiny central nucleus with electrons around it. The nucleus is made up of
protons and neutrons.
Electrons: Negative Charge. -1
Protons: Positive Charge. +1
Neutrons: Neutral...no Charge. 0
Compounds are often stronger than elements as they have no organised structure, which means
some atoms are bigger or smaller than each other and its harder for the atoms to slide past each
other making them have stronger bonds unlike in elements where because they have a set structure
its easier for the atoms to slide past each other, making the bonds weaker.
Atomic structure:
The nucleus of an atom overall has a positive charge. All atoms have the same number of Electrons
and Protons.
Because all atoms contain the same amount of electrons and protons they cancel each other out,
which mean overall the atom has no charge. All atoms have the approximated charge of 0.
Periodic table:
The number of protons in each atom of an element is known as its Atomic number.
The elements in the periodic table are arranged in order of their atomic number (number of protons).
The number of protons and neutrons in the nucleus of an atom is called its Mass number.
Number of neutrons= mass number- atomic number
To work out the number of neutrons:
Arrangement of electrons in atoms
One model of the atom which we use has electrons arranged around the nucleus in shells. Each shell
represents a different energy level. The lowest energy level is shown by the shell which is nearest to
the nucleus.
REMEMBER!
The first shell (closest to the nucleus) can only hold a maximum of 2 electrons, which have to be
placed opposite each other in the shell.
The second shell and the rest following can hold up to 8 electrons, however these are organised in
pairs, as doubles.
Amar Patel 11/1/13

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To save time form drawing atoms, we write down the number of electrons in each energy level, this
is called the Electronic structure.
You can also look at the periodic table
to know what the how many electrons the outermost layer contains, by looking at an elements
group, the periodic table is organised in 8 different groups, showing the number of electrons on the
outer layer, such as oxygen is in group 6 which means it has 6 electrons on its outer shell.…read more

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Sometimes atoms react together by transferring electrons to form chemical bonds. This happens
when metal react with non-metal atoms. If the reacting atoms are all non-metals, then the atoms
share electrons to form chemical bonds.
When a metal bonds with a non-metal, the metal atom gives one or more electrons to the non-metal
atom. Both atoms become charged particles called ions.
Metal atoms form positively charged ions (+)
Non-metals atoms form negatively charged ions (-)
Opposite charges attract, forming strong bonds called ionic bonds.…read more

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Rotary Lime Kiln
To make lots of calcium oxide this reaction is done in a furnace called a lime kiln.
We fill he kiln with crushed limestone
Heat it strongly using a supply of hot air
Calcium oxide comes out of the bottom of the kiln
Waste gases including the carbon dioxide made, leave the kiln at the top
Calcium oxide is often produced in rotary kiln, where the limestone is heated in a rotating drum.…read more

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Neutralising acids
Calcium hydroxide is an alkali. It reacts with acids in a neutralisation reaction. The products of the
reaction are a calcium salt and water.
Calcium hydroxide is used by farmers to improve soil that is acidic. Because it is an alkali, it will raise
the pH of acidic soil. It is also used to neutralise acidic waste gases in industry before releasing gases
into the air.
Cement and concrete
Cement:
Although lime mortar holds bricks and stone together very strongly.…read more

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Sometimes builders add small stones or crushed rocks, called aggregate, to the mixture of water,
cement and sand. When this sets, it forms a hard, rock-like building material called concrete.
This material is very strong, especially good at resisting forces which tend to squash or crush it. By
pouring the wet mixture around steel rods or bars and then allowing it to set makes the concrete
even stronger. Making reinforced concrete, which is also good at resisting forces that tend to pull it
apart.…read more

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Metal oxide + Carbon Metal + Carbon Dioxide
The metal is also formed, as the element:
We call the removable of oxygen from a compound chemical reduction.
Metals that are more reactive than carbon are not extracted from their ores by reduction. The
process used to extract them is called, electrolysis.
Iron and steels
Iron is less reactive than carbon, therefore is extracted using carbon to remove oxygen from the iron
oxide in the ore. We extract iron in a blast furnace.…read more

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It has low density
It is a good conductor of electricity and energy
Its malleable and ductile, which means it can be shaped and drawn into wires easily
Although its reactive it does not corrode easily
This is due to aluminium atoms on its surface react with oxygen in the air; they form a thin layer of
Aluminium oxide, which stops any corrosion taking place
Not all that strong, however can be used to form alloys, the alloys tend to be more stronger, harder
and…read more

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Then we use the impure copper as the positive electrode in the electrolysis cells to make pure
copper.
Metal ions are always positively charged, therefore in electrolysis they are attracted to the negative
electrode. So metals are always deposited at the negative electrode.
Copper sulfate + iron iron sulfate + copper
This method give the very pure copper needed to make electrical wiring. The copper can also be
extracted from copper sulfate solution in industry by adding scrap iron.…read more

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We can make copper and aluminium harder by adding other elements. We usually alloy gold with
copper when we use it in jewellery. Pure gold wears away more easily than its alloy with copper. By
varying the proportions of the two metals we also get different shades of `gold' objects.…read more

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