Give reason for the following: (i) Cutting and piercing toots are made sharp. (ii) An egg sinks in freshwater but floats in highly salty water

(i) Cutting and piercing tools are made sharp because they are able to exert more pressure due to their smaller area of cross-section.
(ii) An egg sinks in freshwater, because the density of the egg is more than the density of freshwater. The highly salty water is quite dense i.e., its density is very large. Thus, the density of egg is now less than the density of water and floats in salty water.