• Atoms of different elements combine in fixed ratios to form compounds, which have different properties from their component elements.

• Mixtures contain more than one element and/or compound that are not chemically bonded together and so retain their individual properties.

• Mixtures are either homogeneous or heterogeneous.

• Deduction of chemical equations when reactants and products are specified.

• Application of the state symbols (s), (l), (g) and (aq) in equations.

• Explanation of observable changes in physical properties and temperature during changes of state.

Guidance:

• Balancing of equations should include a variety of types of reactions.

• Names of the changes of state—melting, freezing, vaporization (evaporation and boiling), condensation, sublimation and deposition—should be covered.

• The term “latent heat” is not required.

• Names and symbols of elements are in the data booklet in section 5.

Utilization:

• Refrigeration and how it is related to the changes of state.

• Atom economy.

• Freeze-drying of foods.

Aims:

• Aim 8: The negative environmental impacts of refrigeration and air

conditioning systems are significant. The use of CFCs as refrigerants has

been a major contributor to ozone depletion.