Chemical Changes – Definitions
Acid: Acids produce hydrogen ions (H+
) in aqueous solutions. They have a pH range of 0-6.
Alkali: Alkalis produce hydroxide ions (OH-
) in aqueous solutions. They have a pH range of
8-14.
Crystallisation: A separation technique used to produce solid crystals from a
solution by
evaporating the solvent.
Displacement: A chemical reaction in which a more reactive element displaces
a less
reactive element from its compound.
Electrolysis: The splitting up of an ionic compound using electricity. The electric
current is
passed through a substance causing chemical reactions at the electrodes and
the
decomposition of the materials.
Electrolyte: A solution containing free ions from the molten or dissolved ionic
substance.
The ions are free to move to carry charge.
Extraction: Extraction techniques are used to separate a desired substance
when it is mixed
with others.
Filtration: A separation technique used to separate solids from liquids.
Negative electrode (cathode): The electrode where hydrogen is produced if the
metal in the
electrolyte is more reactive than hydrogen. It is where positively charged ions
gain
electrons and so the reactions are reductions.
