Question

A block of wood is so loaded that it just floats in water at room temperature. What change will occur in the state of floatation, if (a) some salt is added to water, (b) water is heated ? Give reason.

Answer 1

(a) It will float with some part outside water.
Reason : On adding some salt to water, the density of water increases, so upthrust on a block of wood increases, and hence, the block rises up till the weight of salty water displaced by the submerged part of block becomes equal to the weight of the block.

(b) The block will sink.
Reason: On heating, the density of water decreases, so upthrust on the block decreases and the weight of block exceeds upthrust due to which it sinks