Topic 4: Chemical Changes Flashcards
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.
Neutralisation:
The reaction when an acid and a base react to form water and a salt.
Oxidation:
A reaction involving the gain of oxygen. Oxidation is the loss of electrons.
pH scale:
The pH scale, from 0 to 14, is a measure of the acidity or alkalinity of a solution and can be measured using universal indicator or a pH probe.
Positive electrode (anode):
The electrode where oxygen is produced unless the solution contains halide ions then the halogen is produced. It is where negatively charged ions lose electrons and so the reactions are oxidations.
*Redox reaction:
A reaction in which both oxidation and reduction occur simultaneously.
Reduction:
A reaction involving the loss of oxygen. Reduction is the gain of electrons.
