State which of the following involve a chemical change and which involve a physical change:  making toast, melting chocolate, freezing cordial, water evaporating , putting a solute tablet in...

State which of the following involve a chemical change and which involve a physical change:

 

making toast, melting chocolate, freezing cordial, water evaporating , putting a solute tablet in water, burning gas and cutting up cheese.

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted on

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

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