Question

A wooden block is weighed with iron, such that combination just floats in the water at room temperature. State your observations when:
(1) water is heated above room temperature
(2) water is cooled below 4°C. Give reasons to your answers in (1) and (2).

Answer 1

(1) We know density of water decreases with a rise in temperature and hence upthrust decreases.
(2) The density of water is maximum at 4°C. When the water cooled below 4°C, then its density and hence upthrust acting on it decreases. So, wooden block weighed with iron, sinks more than earlier.