Give reason:
a. fractionating columns with beads are used for fractional distillation
b. crystallisation is a better technique than evaporation

a.The glass beads present in the fractionating column provide a large surface area for hot vapours to cool and condense repeatedly

b.Crystallization is better than evaporation because some solids can decompose or can get burned during evaporation

Explanation:

a.The fractionating column is fitted in the neck of the distillation flask containing the mixture of liquids to be separated

b. Also in some cases impurities can remain dissolved in the solution while evaporation which cannot be removed even after filtration

aquifers are bounded above and below by impermeable rock. the driving force of groundwater movement in confined aquifers is pressure, rather than gravity.