Question

difference between boiling and evaporation

Answer 1

When we  boil water or a liquid, usually there is a lot of movement of liquid molecules, there are bubbles.  At boiling temperature there is an equilibrium existing between the water molecules in the liquid form and vapor form at the top  surface of water.  The water molecules take heat from the heating source.  The temperature remains same.  Heat supplied is converted into the internal energy (latent heat).  

Boiling temperature depends on the pressure of water vapour above the liquid surface.  At  1 atmosphere, water boils at  100 deg.C.  At lower pressure, water boils at 90 deg C or even less.  Boiling takes place at one temperature (depending on pressure).  Boiled fluid molecules are in saturated state.

Evaporation is the process of escape of liquid molecules from liquid state to vapour state across the liquid surface.  Higher temperature increases evaporation rate.  Evaporation can occur at any temperature like, water can evaporate at 15 deg C or 30 deg C or 90 deg C.   We dry our clothes due to evaporation of water from the tiny pores in the clothes.  During the evaporation process, the molecules take some energy from the remaining part of liquid.  So liquid cools down.  Water in a pot or in an open bowl in a room evaporates.

Evaporation process is not an equilibrium process.  The pressure difference in the vapour phase (low) and liquid phase (high), evaporation occurs.  Evaporation occurs at the surface and boiling occurs throughout the liquid.

During evaporation process, temperature may not remain same.  Evaporation reduces a lot, if the air is saturated or if it is humid.  Boiling continues as long as we heat the liquid.

Answer 2

Boiling :
1) It takes place in the entire body 
2) a liquid boils only at a fixed point ie. the boiling point 
3) It is a quick process 

Evaporation:
1) it is a surface phenomenon.
2) it takes place at a range of temperatures 
3) it is  a slow process