State which of the following involve a chemical change and which involve a physical change: making toast, melting chocolate, freezing cordial,...

A physical change occurs when either the phase of the
substance changes, i.e. it changes between being a liquid, solid or gas. Or if in either
of the states it changes shape.

A chemical change on the
other hand involves the formation of a new chemical
compound.

In the cases you have
given:

• making toast(without burning the bread):
  this is a physical change as some of the water in the bread
  evaporates

• melting chocolate: here
  the chocolate changes phase from solid to
  liquid

• freezing cordial: here again
  there is a phase change from liquid to
  solid

• water evaporating: again a
  change in phase from liquid to
  gas

• putting a solute tablet in
  water: the substance dissolves in the water which is a physical change (the assumption
  made here is that the chemicals that making up the tablet do not react with
  water)

• burning gas: a chemical
  change, the gas reacts with oxygen to form other chemical
  compounds

• cutting up cheese: a
  physical change with the shape of the solid
  changing