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 .
Warm solvent and stirring promote quick dissolving . Also with small crystals more of the surface is in contact with the solvent than with large crystals.
