How would you confirm that a colorless liquid given to you is pure water?

To make a saturated solution,$36 \,g$ of sodium chloride is dissolved in $100 \,g$ of water at $293 \,K$. Find its concentration at this temperature. (in $,\%$)

Classify the following into elements,compounds,and mixtures:
$(a)$ Sodium $(b)$ Soil $(c)$ Sugar solution $(d)$ Silver $(e)$ Calcium carbonate $(f)$ Tin
$(g)$ Silicon $(h)$ Coal $(i)$ Air $(j)$ Soap $(k)$ Methane $(l)$ Carbon dioxide $(m)$ Blood

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.

List the points of differences between homogeneous and heterogeneous mixtures.

Differentiate between homogeneous and heterogeneous mixtures with examples.