When dissolving a solid or liquid, as the temperature of the solvent increases, the rate of dissolution?
A. increases.
B. decreases.
C. stays the same.
D. either increases or decreases, depending upon the liquid.

D

Explanation:  As temperature increases, the solubility of a solid or liquid can increase or decrease depending on whether the dissolution reaction is exothermic or endothermic. In endothermic reactions, the net energy from the bonds breaking and forming results in heat energy being absorbed when the solute dissolves in solution.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.