AQA Core Science Chemistry Notes

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Atoms

elements are made of only one type of atom

mixtures contain elements and compounds

compounds contain more than one type of atom

Held together by bonds

Atoms contain equal number of protons and electrons

mass number = number of protons (and neutrons)

atomic number = number of proton and neutrons

number of electrons = mass number - atomic number

Protons (+) and neutrons (=)

in nucleus

electrons orbit the nucleus in shells

elements, same group in the periodic table

same number electrons in their highest energy level, gives them similar chemical properties

Transferring electrons - ionic bonding

Sharing electrons - covalent bonding

Ionic bonding

metal and non-metal

metals -> positive ions

non-metals -> negative ions

opposite charges attract

Covalent bonding

2 non-metals bond

electrons are shared

shared electrons form a bond

no atoms lost or made during a chemical reaction

equations must balance

check an equation is balanced by counting the number of each type on either side

limestone is Calcium Carbonate (CaC03)

Limestone were formed from the remains of plants and animals that lived a million years ago

CEMENT = powdered limestone + clay

CONCRETE = cement + sand + water

Buildings made from limestone suffer damage by acid rain

carbonates react with acid to form a salt, water and carbon dioxide

breaking down a chemical by heating is THERMAL DECOMPOSITION

heat

Calcium --------> Calcium -----> Carbon

carbonate oxide dioxide

Limewater is a test for carbon dioxide

it turns cloudy

Mortar = made by mixing cement and sand with water

Calcium Hydroxide is made from adding water to calcium oxide

Calcium Oxide + Water -----> Calcium Hydroxide

Metals above carbon extracted = electrolysis

Metals below carbon extracted = reduction using carbon

A metal compound within a rock is an ore.

Ores are mined and then purified

copper rich ores

smelting

heat (copper) ore in a furnace with air

copper sulphide +oxygen -> copper + sulphur dioxide

expensive as needs lots of heat and power

copper sulphate

add sulphuric acid to a copper ore

produces copper sulphate

extract copper using electrolysis/displacement

low grade (copper) ores

Phytomining

plants absorb ions from low-grade ore

plants are burned

copper ions dissolved by adding H2SO4

displacement/electrolysis extract pure Cu

Bioleaching

bacteria feed on low-grade ore

produce a waste product, contains copper ions

displacement/electrolysis to extract pure Cu

Atoms

Periodic table and bonding

Chemical equations

limestone and carbonates

Extracting Metals