Which of the following will show 'Tyndall effect'?

What type of mixtures are separated by the technique of crystallisation?

Which of the following materials fall in the category of a 'pure substance'?
$(a)$ Ice $(b)$ Milk $(c)$ Iron $(d)$ Hydrochloric acid $(e)$ Calcium oxide
$(f)$ Mercury $(g)$ Brick $(h)$ Wood $(i)$ Air.

Try segregating the things around you as pure substances or mixtures.

Pragya tested the solubility of four different substances at different temperatures and collected the data as given below (results are given in the following table,as grams of substance dissolved in $100 \,g$ of water to form a saturated solution).

Substance Dissolved	$283 \,K$	$293 \,K$	$313 \,K$	$333 \,K$	$353 \,K$
Potassium nitrate	$21$	$32$	$62$	$106$	$167$
Sodium chloride	$36$	$36$	$36$	$37$	$37$
Potassium chloride	$35$	$35$	$40$	$46$	$54$
Ammonium chloride	$24$	$37$	$41$	$55$	$66$

$(a)$ What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in $50 \,g$ of water at $313 \,K$?
$(b)$ Pragya makes a saturated solution of potassium chloride in water at $353 \,K$ and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.

Explain the following giving examples.
$(a)$ Colloid
$(b)$ Suspension