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Year 9 GCSE C2.1 Overview
Learning Objectives
C2.1.1 Relative formula mass
Define ‘relative atomic mass’ and ‘relative formula mass’
Calculate relative formula masses from formulae
C2.1.2 Empirical formula
Calculate the empirical formula of a compound
Calculate relative formula masses from balanced equations
C2.1.3 Pure and impure substances
Explain what purity means
Explain that many useful materials are mixtures
Use melting point data to distinguish pure substances from impure substances
C2.1.4 Filtration and crystallisation
Describe and explain how filtration and crystallisation work
C2.1.5 Distillation
Describe and explain how simple distillation and fractional distillation work
C2.1.6 Chromatography
Describe how paper and thin layer chromatography work
Calculate Rf values from chromatograms
Describe how gas chromatography works
C2.1.7 Purification and checking purity
Suggest suitable chromatography methods for distinguishing pure from
impure substances
Suggest suitable purification methods when given information about the
substances involved
Year 9 GCSE C2.1 Overview
C2.1 Keywords
Alloy: A mixture of a metal and at least one other element.
Balanced chemical equation: A written model for a reaction that shows the
formulae and number of units for all the substances involved.
Boiling point: The temperature at which a substance changes from the liquid
state to the gas state.
Carrier gas: An unreactive gas such as nitrogen, or inert gas such as helium,
used as the mobile phase in gas chromatography.
Chemical formula: A description of a compound or an element that uses
symbols to represent the atoms present. Numbers show where there are more
than one atom of an element in the substance.
Chromatogram: The pattern produced when separating a mixture using
chromatography.
Chromatography: A separation method that relies on the distribution of a
substance between a mobile phase and a stationary phase.
Condensed: Turned from the gas state to the liquid state.
Condenser: Apparatus that can cool a substance in its gas state to change it
to its liquid state.
Crystallisation: The process by which crystals are formed during evaporation
of a solvent from a solution.
Dissolve: The process in which a solute and solvent mix completely to form a
solution
Empirical formula: Chemical formula showing the simplest whole number
ratio of the atoms of each element in a compound.
Evaporates: Turns from the liquid state to the gas state.
Filtrate: A solution or substance in its liquid state that passes through the filter
during filtration.
Filtration: The process by which insoluble substances are separated from
soluble substances using a filter.
Fraction: A substance separated from a mixture during fractional distillation.
Fractional distillation: A method used to separate a solvent from a mixture of
two or more solvents.
Fractionating column: A piece of apparatus used to improve the separation
of solvents during fractional distillation.
Year 9 GCSE C2.1 Overview
Gas chromatography: A type of chromatography that uses silica or alumina
packed into a metal tube as the stationary phase, and an unreactive or inert
carrier gas as the mobile phase.
Impure substances: Material consisting of two or more different elements
and/or compounds.
Insoluble: Describes a substance that will not dissolve in a given solvent.
Melting point: The temperature at which a substance changes from the solid
state to the liquid state.
Mixture: Material consisting of two or more different substance, not
chemically joined together.
Paper chromatography: Separation method that uses paper as the stationary
phase and a solvent in the liquid state as the mobile phase.
Periodic table: A table in which the elements are arranged in rows (periods)
and columns (groups), in order of increasing atomic number.
Phase: A substance in the solid, liquid, or gas state.
Pure substance: Material consisting of just one element or one compound.
Purity: A measure of how pure a substance is. A 100% pure substance consists
entirely of one element or compound.
Relative atomic mass: The mean mass of an atom of an element compared
to 1/12 the mass of a carbon-12 atom, defined as 12.0 exactly. Its symbol is
Ar.
Relative formula mass: The mean mass of a unit of a substance compared to
1/12 the mass of a carbon-12 atom, defined as 12.0 exactly. It is calculated
by adding together the relative atomic masses for all the atoms in the
formula for the substance. Its symbol is Mr.
Relative molecular mass: The mean mass of a molecule of a substance
compared to 1/12 the mass of a carbon-12 atom, defined as 12.0 exactly. It is
calculated by adding together the relative atomic masses for all the atoms in
a molecule. Its symbol is Mr.
Residue: Insoluble material left behind in the filter during filtration.
Rf values: Relative distance travelled by a substance during
chromatography, calculated as: distance travelled by substance ÷ distance
travelled by solvent.
Saturated solution: A mixture of a solvent and solute that contains the
maximum mass of solute at a given temperature
Year 9 GCSE C2.1 Overview
Simple distillation: A method used to separate a solvent and a solution that
have different boiling points.
Solubility: A measure of how much solute can dissolve in a given solvent at a
certain temperature.
Soluble: Describes a substance that will dissolve in a given solvent.
Solute: A substance that dissolves in a solvent to form a solution.
Solution: A mixture formed when one substance dissolves in another.
Solvent: A substance that can dissolve a solute to form a solution.
Thin layer chromatography: A type of chromatography that uses silica or
alumina spread on a glass or plastic plate as the stationary phase, and a
solvent in the liquid state as the mobile phase.
Vapour: A substance in its gas state and below its boiling point.