Question

Assertion: Water in a beaker cannot be made to boil by placing it in both of boiling water.
Reason: Water in the beaker will be heated to ${100^ \circ }C$ but will not boil as for boiling it requires latent heat of steam which is not provided by water bath as both attains ${100^ \circ }C$.
(A) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
(B) Both Assertion and Reason are correct but Reason is not the correct explanation for
Assertion.
(C) Assertion is correct but Reason is incorrect.
(D) Assertion is incorrect and Reason is correct.

Answer 1

As we know that latent heat of vaporization of a substance is that amount of energy which must be added to the liquid to convert it into a gas without change in temperature and we know that water boils at ${100^ \circ }C$.

Complete Step by step answer:
When water boils the molecules get enough energy and starts moving fast and as the temperature increases the liquid molecules changes to gaseous molecules of water vapour and we also know that water boils at ${100^ \circ }C$. So when the water in the beaker is kept in the water bath of boiling water it already has a temperature of ${100^ \circ }C$so the beaker will only be heated to ${100^ \circ }C$and it will not boil. For boiling it requires some amount of latent heat which will not be provided by the boiling water bath so both will attain equilibrium. Hence the Assertion is true.

As we have already discussed that water in the beaker will be heated to the same temperature of water bath which is ${100^ \circ }C$ but it will not boil because for boiling it requires latent heat of steam which is not provided by the water bath as they both attains thermal equilibrium. Therefore the reason is also correct.

Hence the correct answer is (A).

Note: Water baths in laboratories are used instead of using any direct flame because it is a good heating source for flammable substances thereby preventing ignition. For instance- alcohol is a highly flammable substance and its vapours are even explosive thus for heating alcohol water bath is used as it provides a constant temperature and a gentle slow heat to boil hence prevents any damage in laboratory conditions.