Evaporation is the process where water changes from a liquid to a gas or vapor. It is part of the water cycle, where water vapor moves from liquid water back into the atmosphere. For evaporation to occur, molecules at the water surface need energy to break hydrogen bonds and escape into the air through diffusion and transport. The rate of evaporation depends on factors like temperature, humidity, and surface area exposure to air.

1. EVAPORATION
Evaporation is the process by which water changes from a liquid to a gas or vapor. Evaporation is the primary pathway that
water moves from the liquid state back into the water cycle as atmospheric water vapor. It is a net process because water
vapor is constantly moving back and forth from the water surface. Evaporation occurs when there are more molecules
leaving the water surface then entering. It takes energy for a molecule to break a hydrogen bond and escape the water
surface. 1) Energy input to the water to supply heat (i.e., increase the kinetic energy so molecules can escape). 2) Diffusion
of water vapor molecules from the water surface to the atmosphere. 3) Transport of water vapor molecules away from the
water surface.

2. ACKNOWLEDGEMENTS AND
SOURCES-
A big thanks to Shamsad Begam and our respected teachers
Dr.Anirban Roychowdhury ,Dr.Sandip Bhattacharyya for the
information and ideas…
SOURCE-
www.scientificamerican.com/article/chilling-science-evaporative-
cooling-with-liquids/
www.ncbi.nlm.nih.gov/pubmed/26684127
www.ncbi.nlm.nih.gov/books/NBK541107/

3. EVAPORATION AND SURFACE AREA
Evaporation occurs when molecules get enough energy from heat to escape the liquid. ... An increased surface area
means that more liquid will be exposed to air at one time, and therefore, more water can evaporate in a given time
period.The humidity is related with the amount of water vapours present per unit amount of the dry air. Now with
increase in the humidity means that we are moving towards saturation or intake ability of molecules decreases and at
saturation no more water vapours can enter. at a given temperature, air can accommodate only a certain definite,
saturation concentration of water molecules take water in a beaker natural evaporation - water molecules tearing the
free water surface and disappearing into the surrounding air - starts but, if this surrounding air is already humid, it will
not be able to accommodate many more water molecules concentration of water molecules soon reaches its saturation
value any further water molecule coming from the water body will make a molecule in the air to fall back into the water
body.The rate of evaporation depends on the concentration of water vapor near the surface. The higher it is, the slower
the rate of evaporation and vice versa.

4. SWEAT AND EVAPORATION
When the temperature rises, your sweat glands (some 2 to 4 million of them) spring into action, making perspiration.
Sweating is your body's natural way of keeping you cool. Some sweat evaporates from your skin, taking heat with it. The rest
runs down your face and body. You feel hotter when it's humid because the wetter air leaves less room for the sweat to
evaporate off your body. The necessary heat of evaporation is extracted from the sweat itself, which leads to a heat transfer
from the liquid into the gaseous state. This results in a cooling effect (called evaporative cooling) that helps to
maintain body temperature and cools the body down when it gets too hot.In winter the sweat evaporate quickly so our skin
get dry and dehydrated and in summer the sweat cannot evaporate quickly so the water droplets remains on our skin..

5. HAND FAN MECHANISM OF ACTION ..
By blowing this layer away with a fan, vapor molecules cannot return to the liquid, so the net rate of evaporation increases.
A similar phenomenon happens to remove heat from dry skin. The “boundary layer” of air just above your skin is hot, and
slows down the rate of heat loss. It acts as an insulator. A fan blows this layer away (though not entirely), accounting for the
wind-chill effect. The airflow on human skin increases evaporation which has a cooling effect due to evaporation heat. It
enhances the circulation of heat by displacing warm and saturated air around the skin,when the air temperature in a given
environment is lower than the skin temperature. We can create airflow by hand fan. The material used must be lightweight
so that it is easily oscillate back and forth and the area must be large so that it can displace more air. Normally the circle has
more area than other shapes, so the circular or semi-circular shape will displace air most effectively or large amount . The
more evaporation of water from the surface will be higher the body will be cooled more.