Question

Give reason for the following statement :
Aquatic animals are more comfortable in cold water than in warm water.

Answer 1

Hint: Aquatic animals like all other beings require to respire using gases like oxygen and nitrogen so we can check at which temperature of the water has the maximum amount of these gases.

Complete answer:
The amount of gases present in water is given by their solubility because where the gases are more soluble, they will be present in large quantities.
Solubility of oxygen and nitrogen in water decreases with increase in temperature since the dissolution is an endothermic process (heat is absorbed). This is because as the temperature rises, the dissolved oxygen molecules (air molecules) begin to boil out of the solution (sea) and reduce their amount in the water.
It can also be said in terms of Henry's constant represented by ${K_H}$.
According to Henry’s law:
${K_H} \propto Temp$
And ${K_H} \propto \dfrac{1}{{so\operatorname{lub} ility}}$
Where ${K_H}$ = Henry’s constant
$ \Rightarrow Temp \propto \dfrac{1}{{So\operatorname{lub} ility}}$
This means when the temperature increases (warms) the solubility of gases in water decreases.
So it is clear from the above discussion that gases are less soluble in warm water.
Therefore, it can be concluded that Aquatic animals are more comfortable in cold water because the dissolved gases (mostly oxygen and nitrogen) in cold water is more, when compared to that of warm water.
And aquatic animals require these gases to carry out general life processes like breathing etc. like every other living being.

Note: Also at a given pressure the solubility of oxygen in water increases with decrease in temperature. The presence of more oxygen at a lower temperature makes the aquatic species more comfortable in cold water.