Water Evaporation Rate

name        jamie
status       student
grade        4-5
location     NC

Question -   I done an experiment to see what type of water
would evaporate the fastest. i put one teaspoon of each substance
in a cup with the same amount in each cup. i used
sugar,salt,pepper,vinegar,vegetable oil, and algae and normal tap
water. the algae water actually evaporated faster but i don't
understand why. is it because algae is considered a plant and it
fees off the water by absorption?
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    For a start, your experiment is a very difficult one, because the
differences are likely to be very small. Students are often tempted to
measure the "rate" at which some process occurs. "Rates" are very tricky
because they depend upon variables that are out of control of the
experimenter. In your case for example, temperature is not mentioned. But
temperature can be the most important factor controlling the "rate" of
evaporation -- more important than any of the other variables. In addition,
the relative humidity will be a very important factor, as will the flow of
air over the surface of the water.
    Your teacher should be able to give you more guidance to provide more
controlled condition. Otherwise, you are likely to end up with results that
can't be easily interpreted.

Vince Calder
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