How do you express concentration of a solution?
Concentration of a solution may be expressed in terms of percentage by mass of solute per 100 gram of the solution. 
Thus, if a solution is 5%, it means it is 5 gram of a solute dissolved in 100 gram of the solution or it contains 5 gram solute and 95 gram solvent.
Concentration of a solution may also be expressed as mass of solute dissolved in 100 cm3 of the solution. Thus, 10% sugar solution by volume means 10 g sugar dissolved in 100 cm3 of solution.
How do you establish that air is a mixture and not a pure substance?
Give the distinguishing features of a pure substance or a compound and a mixture.
List the various types of homogeneous and heterogeneous mixtures with examples.
How will you prepare a saturated solution of copper sulphate in water at 50°C? What will happen if this solution is allowed to cool?
