IGCSE Chemistry Definitions
Terms in this set (67)
Solid changing into a liquid
Liquid changing into a solid
Gas/vapour changing into a liquid
Liquid changing into a gas/vapour
Temperature at which a solid turns into a liquid
Temperature at which a liquid changes into a solid
Temperature at which a liquid changes into a vapour at atmospheric pressure
The random movement of particles from an area of a high concentration to an area of low concentration
Separating an insoluble solid from a liquid
is fluid that has passed through a filter.
the material that dissolves in a solvent to form a solution.
the mixture formed when a solute dissolves in a solvent.
the liquid in which the solute dissolves to form a solution.
Separating liquids of different boiling points by evaporation and condensing
The coating of iron by zinc to protect from rusting. A type of sacrificial protection.
Atomic number/Proton number
The number of protons in an atom
The smallest unit of an element, having all the characteristics of that element
Mass number/Nucleon number
The sum of the protons and neutrons
The centre of the atom which contains protons and neutrons
Atoms of the same element with the same atomic number and different number of neutrons
Made of only one type of atom
Made of two or more different atoms chemically joined together
Made of two or more different components which are not chemically joined together
The columns in the Periodic Table. The Group Number equals the number of electrons in the outer shell
The rows of the Periodic Table. The Period Number equals the number of shells used by the electrons of the atom.
Transfer of electrons so as to achieve a full outer shell o felectrons. This results in the formation of ions.
Sharing of an electron pair between atoms. This results in the formation of a simple covalent molecule or a giant covalent structure.
A charged particle resulting from ionic bonding. The number of electrons are not equal to the number of protons.
A particle formed from covalent bonding which is neutral.
Rate Of Reaction
Change in product or reactant concentration per unit time. The more frequent the collision of particles the greater the rate of reaction.
Substance which increases the rate of reaction without chemically being changed. It lowers the activation energy of the reaction.
A biological catalyst e.g. Amylase
Relative Formula Mass
The sum of the atomic masses of elements in a compound. The formula mass expressed in grams.
One mole of a substance contains the same number of molecules/atoms as in 12 grams of carbon-12. This number (of atoms or molecules) is known as the Avogadro constant (NA) which is equal to 6.02 x 1023
A reaction which gives out heat (ΔH is negative)
A reaction which takes in heat (ΔH is positive).
A scale of 0 - 14 which identifies solution as acidic, neutral or alkaline.
A substance with a pH higher than 7, they react with acids to form a salt and water (called neutralization). Metal hydroxides, oxides and carbonates are all bases.
They have a pH less than 7 and neutralize bases or alkalis to form salt and water. Acidity is caused by a high concentration of hydrogen ions.
They have a pH greater than 7 and neutralize acids to form salt and water. They have a high concentration of hydroxyl ions (OH-). They are soluble bases.
A reaction where acids react to form salts and water. H+ + OH- → H2O
A reaction where a substance burns in oxygen combining to form the oxide and giving out energy.
A reaction where a more reactive element displaces a less reactive element from a solution of its compound.
A reaction where a compound is broken down into simpler substances using heat e.g. Metal carbonates → Metal Oxide + Carbon Dioxide
A reaction where oxygen is added to a substance e.g. Copper + Oxygen → Copper Oxide. Oxidation also means a loss of electrons.
A reaction where oxygen is removed from a substance. Reduction also means a gain in electrons.
is the break-down of a substance or solution by electricity
a molten or aqueous solution through which an electrical current can flow.
The positive terminal (electrode).
The negative terminal (electrode)
negative ion (attracted to the anode)
Positive ion (metal) attracted to the cathode.
A reaction where reactants change to products which can then change back to reactants.
The state of a reversible reaction when the rate of the forward reaction is equal to the rate of the backward reaction.
Chemical compounds (e.g. Ammonium compounds) which are added to soil to increase the quantity and quality of crops.
Process where lakes and rivers which are rich in nutrients due to leaching of fertilizers, encourages the growth of plant life which is decomposed by bacteria using oxygen in the water.
A mixture of hydrocarbons formed from the remains of dead sea life which was covered with silt on the sea bed and compressed over millions of years
A substance formed from the dead remains of plants or animals which will burn in air e.g. Coal, natural gas
A substance which contains carbon and hydrogen atoms only.
Process where long chain hydrocarbons of little value are broken down by heat and a catalyst into smaller, more useful hydrocarbons
A hydrocarbon which only has single covalent bonds between all atoms.
A hydrocarbon which has at least one double bond between two neighbouring carbon atoms.
A saturated hydrocarbon e.g. CH4 - methane
An unsaturated hydrocarbon e.g. C2H4 - ethene
A reaction where many small alkene molecules (monomers) join up to form a long chain molecule of repeating units (polymer).
A reaction where different monomers join up to form a long chain molecule of repeating units (polymer) whilst also producing smaller molecules.
a group of molecules with similar physical and chemical properties, the same general formula and the same functional group (albeit with trends e.g. increasing boiling point with increasing carbon chain length)
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