The purpose of this experiment was to compare the effect of wind speed,
air humidity, and water temperature on the evaporation rate of water.
I became interested in this idea because I knew that water evaporation
could be helpful when it cooled you down and harmful when it dehydrated
both plants and people, so I decided to learn more about what affected
The information gained from this experiment could help food producers
who dehydrate fruit, vegetables, or meat. It could also help
coaches and athletes who need to keep cool during strenuous exercise,
and people who are interested in outdoor activities, such as camping,
hiking, or swimming.
My hypothesis was that the temperature of the air would affect
evaporation rate most.
I based my hypothesis on a diagram I found in Young Scientist
Encyclopedia. The diagram showed that the warmer the water, the
more molecules escaped as vapor.
I also based my hypothesis on a slideshow I saw on the movie “Bill Nye
the Science Guy: The Water Cycle.” It showed that boiling
water’s molecules have more energy and escape as vapor at a much faster
pace than molecules at room temperature.
The constants in this study were:
• The type of water (tap)
• The amount of water
• The location the water is placed
• The size of the container
• The ruler
• The number of trials conducted
• The type of the container
• How long the water has to evaporate
The manipulated variables were air humidity, wind speed, and water
The responding variable was the amount of water evaporated in 150
minutes. I measured the water in a graduated cylinder before and
after the evaporation occurred.
To measure the responding variable, I measured the water in milliliters
before and after the evaporation occurred.
|Small room fan
|Liters tap water
|Small air humidifier
|100 ml. graduated cylinder
|plastic jug (approx. 4
1. Collect materials.
2. Stabilize and maintain the humidity in testing
room using a small air humidifier as needed. For the first phase
of testing, the humidity should be about 34%.
3. Stabilize and maintain the temperature in testing
room. For the first trials the room temperature should be
4. Stabilize and maintain the air speed in testing
room using a small fan as needed. For the first trials the wind
speed should be “dead calm”.
5. Place a jug of tap water in the testing room so it
adjusts to the room temperature. Whenever the water temperature
is the same as the air temperature, the experiment can continue.
6. Pour 100 ml. of tap water from the jug at the
current temperature into each of 5 identical small dishes using a
7. Place the dishes so they are being equally
affected by room temperature, humidity, and air movement.
8. Using a timer, let the water sit in the testing
room for 180 minutes.
9. Using a graduated cylinder, measure the water
remaining from each dish and subtract each from the original 100 ml.
10. Record this as how many milliliters evaporated
for that trial.
11. Repeat steps 4-10, except turn the fan on to its
high-speed setting. Be careful when placing the dishes that all
are equally affected by the moving air.
12. Repeat steps 3-11, but stabilize and maintain the
temperature at 20º C.
13. Repeat steps 3-11, but stabilize and maintain the
temperature at 30º C.
14. Repeat steps 2-13, but stabilize and maintain the
humidity at about 65% for the entire
series of trials.
The original purpose of this experiment was to compare the effect of
wind speed, air humidity, and water temperature on evaporation rate of
The results of the experiment were that wind speed affected evaporation
rate most. The difference between the two wind speeds evaporated
water is 4.4 ml.
See the table and graph below.
My hypothesis was that the temperature of the air would affect
evaporation rate most.
The results indicate that this hypothesis should be rejected, because
wind speed affected evaporation rate most. The temperature of the
air did not matter nearly as much as the wind speed and air humidity in
the room when you are testing evaporation rate.
After thinking about the results of this experiment, I wonder if the
size of the room would affect how much water was evaporated.
Water in dishes set in a closet might evaporate very differently than
in a gymnasium. All liquids can evaporate but they do so at
varying rates. It would be interesting to see what happens to a fast
evaporating liquid like rubbing alcohol using my same procedures.
If I were to conduct this project again, I would do many more trials of
each variation. I would still use five dishes at a time, but I
would do at least three different batches of five for each temperature,
wind speed, and humidity condition. I am sure that each
evaporation trial should have been much longer, probably five to eight
hours long. That would have given a better idea of what happened
with each condition. It would also have been better to add an
intermediate wind speed, about halfway between high and zero.
Evaporation effects how people live every day. It affects profits
for people like food dehydrators, who need evaporation to dehydrate the
food. It also affects the health of humans and animals that need
a sufficient water supply to live.
II. States of Matter
The three main states of matter are liquids, (such as water), gases,
(such as oxygen), and solids (such as wood.) All three of these
states are made up of microscopic particles, but the behaviors from
particles differ in the three phases.
The particles in solid objects are tightly packed, and they are
normally in a regular pattern. Although the particles will
vibrate, they generally do not move from place to place. Solids
can change their shape only if great force is applied. For
example, sawing wood, chiseling rock, cutting diamonds, or burning coal
can alter the shape of a solid.
Liquid molecules are close together without any regular
arrangement. Even though the particles can move about, they can
only just slide past each other. When liquid is put into a
container the particles assume the shape of the container.
Liquids can flow, spill, or pour, but they cannot be held without a
Gas also assumes the shape of the container it is put into.
Molecules in gas are well separated, and like liquid particles, they
have no regular arrangement. Gases also vibrate, but they move
freely at high speeds. Unlike solids and liquids, gas is usually
Elements and compounds can move from phase to phase when a special
physical force is present, such as heat energy. A phase in the
states of matter changes when the temperature does; as the temperature
rises, matter will move to a more active state.
Evaporation is the process in which a liquid turns to a gas by
increased molecular energy.
Energy in the form of heat causes evaporation. Any amount of heat
will cause water to evaporate, although water evaporates faster at a
Molecules of all substances have a certain amount of kinetic energy,
which provides heat to or receives heat from its surroundings,
including nearby molecules. The more energy the molecules gather,
the faster the molecules move, which makes it possible to break the
bonds that hold them together. The molecules then have enough
energy to escape from the substance’s surface as vapor, hence, causing
The wind transports water all around the earth when it is in vapor
form. This action influences the humidity of the air throughout
Approximately 80% of all evaporation is from the oceans. The
remaining 20% is from inland water and different vegetation.
The opposite of evaporation is condensation. It occurs when vapor
molecules lose energy and reform as a liquid.
Evaporation is a phase in the hydrological cycle, or the water
cycle. There are four main phases in the hydrological cycle:
evaporation, condensation, precipitation, and collection.
Evaporation, the first phase, is when a liquid substance turns to vapor
when heated. Condensation happens when the vapor reaches the
clouds, cools off, and changes back to a liquid. Precipitation
occurs when the water falls back to earth as rain, sleet, snow, hail,
or frost. Collection, the last phase in the hydrological cycle,
is when the water runs downhill and collects in lakes, rivers, streams,
seas, or oceans.
Many things influence evaporation rate. If the air already has a
high concentration of the substance evaporating, then the given
substance will evaporate slower. If the air is already saturated
with other substances, almost none will evaporate. Another thing that
influences evaporation rate is the temperature of the substance,
because the hotter the substance, the faster the substance
evaporates. The flow rate of air affects evaporation rate because
if fresh air is moving over the substance all the time, then the
concentration in the air just above is less likely to go up with time,
encouraging faster evaporation. Inter molecular forces also
affect evaporation rate. The stronger the forces that are keeping
the molecules together in a liquid or solid state, the more energy that
must be input to evaporate them.
II. The Laws of Thermodynamics
The first law of Thermodynamics states, in short, you cannot create or
destroy energy. Energy can change from one form to another, like
electricity converting into heat, or heat converting into light.
The second law of Thermodynamics is that energy can flow only one
“Energy spontaneously tends to flow only from being concentrated in one
place to becoming diffused or dispersed and spread out.”
In other words, heat energy moves toward neighboring regions having
So, in conclusion, evaporation affects many humans’ and animals’ life,
health, and profits. Evaporation dehydrates food for profits and
keeps people with a renewable supply of water. Heat, wind speed,
and humidity (saturation) all affect evaporation rate.
“Evaporation and Condensation.” Young Scientist
“Evaporation System Information.”
“Evaporation: the Conversion of Water.” October 26, 2005.
Fox, Mary Anne. “Evaporation.” World Book Encyclopedia.
Book of Science. New York: Arco Publishing, Inc.
Kahl, Jonathon D. Weather
Watch-Forecasting the Weather. Lerner Publications Company
Kahl, Jonathon D. Wet
Weather. Minneapolis: Lerner Publications Company, 1992
“States of Matter.” http://www.ajkids.com/main/followup.asp?aj
“States of Matter.”
Heritage Student Dictionary. Houghton Mifflin Company. Boston.
“The Second Law of Thermodynamics.” January 18, 2006.
“The Water Cycle.” Rabbit Ears Productions. 1995.
“What is Matter.” November 2, 2005.
I would like to thank the following people for helping make my project
• My parents for helping me with my project and
giving me ideas.
• Mr. Newkirk for providing me with the thermometer
that made my experiment possible and correcting my written work.
• Jordan, Tensie, Kacey, and Taylor, for helping me
when I couldn’t find information.
• Mrs. Viernes for helping me whenever I had a
problem with my computer.
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