AQA Chemistry Unit 1 Revision Notes

Revision notes for the whole of unit 1 in AQA chemistry but useful for other boards too made by me and my best friend.

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Ambassador Fundamental ideas!
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: 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
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.

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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.…read more

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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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Oxygen O
The chemical properties in an atom depend on how many electrons it has. The way an
element reacts is determined by the number of electrons in its highest energy level.
Therefore elements in the same group that have the same number of electrons on their
outer shell, react in the same way.
Forming Bonds
Sometimes atoms react together by transferring electrons to form chemical bonds. This
happens when metal react with non-metal atoms.…read more

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Word equations are only useful if everyone who reads them speaks the same
· Word equations do not tell us how much of each substance is involved in the
· Word equations can get complicated when lots of chemicals are involved
The total mass of the products formed in a reaction is equal to the total mass of the
reactants. Therefore it is important to balance equations.…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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Calcium carbonate + Hydrochloric acid calcium chloride + water + carbon dioxide
Carbonates react with acids to give a salt, water and carbon dioxide.…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
Although lime mortar holds bricks and stone together very strongly.…read more

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There is also the possibility of use as landfill sites
for household rubbish before covering with soil and replanting.
Metals and their uses:
Extracting metals
Metals are found in the earths crust. We find most metals combined chemically with other
chemical elements, often with oxygen. This means that the metal must be chemically
separated from its compounds before you can use it.
Some rocks have enough metal or metal compound worth extracting, we often call these
rocks a Metal ore.…read more

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Because carbon is more reactive than each of these metals, we use carbon to extract the
metals from their oxides. We must heat the metal oxide with carbon. The carbon removes
the oxygen from the metal oxide to form carbon dioxide.
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.…read more


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