AQA Core Science Chemistry Notes

Atoms

elements are made of only one type of atom

mixtures contain elements and compounds

compounds contain more than one type of atomHeld 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 tablesame number electrons in their highest energy level, gives them similar chemical properties

Transferring electrons - ionic bondingSharing electrons - covalent bonding

Ionic bondingmetal and non-metalmetals -> positive ionsnon-metals -> negative ionsopposite charges attract

Covalent bonding2 non-metals bondelectrons are sharedshared 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 raincarbonates react with acid to form a salt, water and carbon dioxide

breaking down a chemical by heating is THERMAL DECOMPOSITION

               heatCalcium --------> Calcium -----> Carboncarbonate              oxide             dioxide

Limewater is a test for carbon dioxideit 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 oressmelting 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) oresPhytomining 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