Define and compare evaporation and boiling.

Evaporation is the process of conversion of a liquid into vapor at a temperature below its boiling point. It is a surface phenomenon. Boiling is the process by which a liquid turns into a vapor when it is heated at its boiling point. It occurs only at a particular temperature - boiling point.

So the difference between the two is, 1, boiling can occurs everywhere, depending on the heat source. Whereas evaporation only takes place at surface of the liquid.

2, boiling requires certain temperature at certain pressure, and continuous heating source, while evaporation works at any temperature and pressure.

3, evaporation is a slow and soft process, while boiling is violent and fast.

4. Wind and surface area affect evaporation. Wind and surface area do not affect boiling

Explanation: To begin with, i’ll talk about this two phenomena first.

When the liquid get heated, tiny vapor bubbles come out around the condensation nucleus in liquid, which could be air in water or ashes. Vapor has its pressure at certain temperature, which is called Saturated Vapor Pressure. When the vapor pressure is lower than the pressure that vapor bubbles received from out side, such as the air pressure (and the liquid pressure considering the depth of liquid, however, in most cases, the liquid pressure is much too low), the bubbles stay there and waiting. As long as the Saturated Vapor Pressure in vapor bubbles reach the same as air pressure, the vapor bubbles will unstoppablely expand and move up, and that’s how boiling works.

But for the evaporation, it occurs on the surface of liquid. The molecules of liquid move at the surface of liquid. Most of the molecules are trapped by intermolecular forces, whereas a few molecules escaped to the air as vapor. Meanwhile, some vapor molecules move back to the liquid surface and are trapped by the liquid again. So if the escaping rate is higher than the tracpping rate, this is how evaporation works. if you blow a liquid, the vapor on that area is gone, and the evaporation speeds up.

Sorry if this was a bit long, wanted to include as much detail as possible! Hope I could help! :)

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

answer; talc and gypsum;