Atoms
Fraction
The smallest part of an element that can
take part in chemical reactions.
A component of a mixture that has been
separated by fractional distillation.
Chromatogram
Fractional distillation
The piece of paper showing the results of
carrying out chromatography on a
substance.
A method a separating a mixture of liquids
with different boiling points into
individual components (fractions).
Chromatography
Fractionating column
A technique for separating the
components of a mixture, for example
different food colouring agents. It works
because dissolved substances move at
different rates through a piece of paper
soaked in a solvent.
A long column used to separate a mixture
of liquids into different fractions with
different boiling points. The column is
warmer at the top than at the bottom.
Covalent bond
A bond between two non-metal atoms
made up pf a shared pair of electrons- one
from the outermost shell of each atom.
Diamond
A form of carbon that is very hard and
doesn’t conduct electricity. It is used in
cutting tools.
Giant molecular covalent substance
Substances containing millions of atoms
all held together by covalent bonds.
Graphite
A form of carbon that is soft and conducts
electricity. It is used as a lubricant as the
layers slip over each other easily.
Immiscible
Liquids that do not form a solution but
separate into two layers.
Dissolve
This occurs when a solute splits up and
mixes with a solvent to make a solution.
Liquefy
Convert a substance into a liquid by
heating or cooling.
Dot and cross diagram
A way of showing electronic structures in
covalent substances, using dots and
crosses to represent the electrons from
different atoms.
Lubricant
Double bond
Miscible
When two bonds join a pair of the same
atoms (usually two carbon atoms).
Liquids that completely mix together to
form a solution.
A substance placed between two moving
surfaces to reduce the friction between
them.
Molecule
Two or more atoms joined together by
covalent bonds.
Rf value
The ratio of the distance travelled by a
solute on a chromatogram (measured
from the centre of the spot) to the
distance travelled by the solvent under
the same conditions. Also called
retardation factor. The Rf value for a
substance can be used to identify
compounds.
Simple molecular covalent
substance
A substance made of individual small
molecules, with strong covalent bonds
holding the atoms together in the
molecules but only weak forces between
neighbouring molecules.
Soluble
A substance which dissolves in a given
solvent.
Solution
Separating funnel
The clear mixture that forms when a
solute dissolves in a given solvent.
A funnel with a tap on the bottom that is
used for separating immiscible liquids.
Solvent
The liquid that dissolves the solute.
Solute + Solvent = Solution