1. Ice floats on water.
On liquid, molecules are associated with each other irregularly containing Hydrogen Bond. When liquid is cooled into ice, the molecules arrange themselves in regular form and due to change in arrangement, empty spaces are left among molecules. When water is converted into ice, it’s volume increase about 9% and density decreases, so ice floats on water.
2. Evaporation is cooling process.
During evaporation, those molecules evaporate, which have high Kinetic energy, leaving behind those having low Kinetic energy, therefore temperature of remaining liquid falls. Hence evaporation is a cooling process.
3. Earthenware vessels keep water cool.
Earthenware vessels have small pores in their walls through which water evaporates taking high energy molecules and leaving behind low energy molecules, so remaining water becomes cool.
4. Steam causes server burns than boiling water.
Water has high heat of vaporization. Heat of vaporization of water is 40.7 kJ/mol. It is therefore steam has more temperature than boiling water. When water boils its temperature does not increase but that heat is converted into steam and more heat is accumulated into steam.
5. Falling drop of liquid is spherical.
The falling drop of liquid is spherical due to surface Tension. The inward forces on the surface of molecules reduce the surface to volume ratio, so shape of molecule becomes spherical when it falls.
6. Food is cooked more quickly in pressure cooker than in a covered pot.
In pressure cooker, water vapours do not find escape to go outside so more pressure develops and boiling point is increased and food cooks quickly. But in covered pot water vapours find escape to outside and no such pressure is developed so food cooks slowly in compare of pressure cooker.