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Author: Jane Healey

Evaporation is the process of water transferring from a liquid to a gas and is the primary method for water to move into the atmosphere during the water cycle. Scientists believe that the earth’s oceans, seas, lakes and rivers provide 80-90% of the moisture in the atmosphere. The rest comes from plant transpiration.

In this experiment, the independent variables include heat and air flow. The dependent variable is the rate of evaporation measured in time. The constants include the sponges, the plastic plates and the amount of water.


What is the effect of wind and temperature on the evaporation rate of water? These two elements will be tested separately and combined to assess the overall range of effects.


  • Four sponges of the same size
  • Water
  • Measuring cup
  • Plastic plates
  • Electric fan
  • Portable electric heater
  • Timer or clock
  • Logbook


  1. Place a dry sponge on each of the four plates.
  2. Pour half a cup of water on each sponge.
  3. Put one sponge aside to act as the control.
  4. Place one sponge in front of the electric heater. Be careful that the plate is not too close and that other fire hazards have been cleared.
  5. Place one sponge in front of the electric fan. As with the heater, be careful about hazards.
  6. Place one sponge in front of both an electric heater and an electric fan. (This step may be completed separately to avoid needing two heaters and two fans.)
  7. Check the sponges at regular intervals, keeping track of the time each sponge requires to dry.
  8. The experiment can be repeated and the results averaged for more accurate times. Additionally, the fan speed and heater temperature can be modulated to discover the rates for increased intensity of both.
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