Flask is immersed in a large beaker of very hot water. At first, the level of the liquid in the tube falls, but after a short time it rises. Explain why the liquid level in the tube stops falling and starts to rise.

Explanation:

When a flask is dipped in very hot water in a large beaker , the flask expands due to heat gain . As a result , level of water in tube fitted in flask goes down .

After some time , the water inside tube also become hot so it expands  . coefficient of volume expansion of water is more than coefficient of volume expansion of glass . Hence greater expansion takes place in the volume of water . It is due to this fact that water level in tube starts rising after some time of fall .