Calculate the mass of water and mass of glucose required to make $250 \, g$ of $40 \%$ solution of glucose.

$(a)$ Illustrate with an example that physical and chemical changes can take place together.
$(b)$ Which of the following are chemical changes?
$(i)$ Mixing of iron filings and sand
$(ii)$ Growth of plant
$(iii)$ Rusting of iron
$(iv)$ Freezing of water

$(a)$ What separation technique will you apply for the separation of the following?
$(i)$ Ammonium chloride from sodium chloride.
$(ii)$ Different pigments from the extract of flower petals.
$(b)$ What is crystallisation? List two ways in which the crystallisation technique is better than the simple evaporation technique.

Colloids are quite stable. Name the process by which you can separate the components of a colloidal solution.

How will you separate a mixture of naphthalene powder and common salt? Draw a neat and labelled diagram to show the process.

How is a pure substance different from a mixture?