How to Show Experiments to Demonstrate Evaporation

Evaporation can seem like an invisible process, but these simple experiments can make it visible and demonstrate the factors that control it. These are great for a classroom or at-home science project.

1. The Disappearing Water (Demonstrating Evaporation)

• Materials: A clear glass, water, a marker.
• Procedure:
  1. Fill the glass about halfway with water.
  2. With the marker, carefully draw a line on the outside of the glass marking the exact water level.
  3. Place the glass on a windowsill or shelf where it won't be disturbed.
  4. Check the glass every day for several days.
• Observation: You will see the water level slowly drop below the line you drew.
• Conclusion: The water is disappearing because it is evaporating (turning into water vapor) and mixing with the air.

2. The Surface Area Race (Demonstrating Surface Area)

• Materials: Two paper towels, a measuring cup, a plate, a small glass.
• Procedure:
  1. Measure an equal, small amount of water (e.g., 2 tablespoons or 30ml).
  2. Pour one measure of water into the small glass.
  3. Pour the other measure of water onto the plate and spread it out. (Alternatively, pour each onto a separate paper towel, one bunched up and one flat).
  4. Leave both and observe which one dries up first.
• Observation: The water on the plate or the flat paper towel will evaporate much faster than the water in the glass or on the bunched-up towel.
• Conclusion: A larger surface area exposes more water to the air, which dramatically speeds up the rate of evaporation.

3. The Effect of Wind (Demonstrating Wind Speed)

• Materials: Two plates, water, a fan (optional).
• Procedure:
  1. Pour an equal, small amount of water onto two identical plates.
  2. Place one plate in a calm spot.
  3. Place the second plate in front of a fan or in a naturally windy/drafty spot.
  4. Time how long it takes for each plate to dry.
• Observation: The plate in front of the fan will dry much more quickly.
• Conclusion: Wind (air movement) increases the rate of evaporation by blowing away the humid air layer just above the water's surface.

4. The Effect of Heat (Demonstrating Temperature)

• Materials: Two plates, water.
• Procedure:
  1. Pour an equal, small amount of water onto two identical plates.
  2. Place one plate in a warm, sunny spot (like a sunny windowsill).
  3. Place the second plate in a cool, shady spot (like a closet or under a table).
  4. Check back every 30 minutes.
• Observation: The water in the sunny spot will evaporate much faster.
• Conclusion: Higher temperature (heat) increases the rate of evaporation.

5. The Cooling Glove (Demonstrating Evaporative Cooling)

• Materials: Two thin gloves (or socks), water, a fan.
• Procedure:
  1. Put on both gloves. Keep one dry.
  2. Dip the other gloved hand in water so the glove is damp (not dripping).
  3. Hold both hands up in the air, preferably in front of a fan or in a breeze.
• Observation: The wet-gloved hand will feel noticeably, and sometimes uncomfortably, colder than the dry hand.
• Conclusion: The water evaporating from the wet glove is drawing heat energy directly from your hand, causing a cooling sensation. This shows evaporation is a cooling process.