Simple classroom experiment to demonstrate evaporation

Experiment: The Two Plates Race

Objective: To show how factors like surface area and wind speed affect the rate of evaporation.

Materials Needed:

• Two identical small plates or saucers
• One tall, narrow glass or test tube
• A measuring cup or graduated cylinder
• Water
• A small fan (optional)
• A sunny window (optional)

Procedure:

Part 1: Demonstrating Surface Area

1. Measure an equal, small amount of water (e.g., 20 ml).
2. Pour the water into the tall, narrow glass.
3. Measure the same amount of water (20 ml) again.
4. Pour this water onto one of the flat plates, spreading it out.
5. Place the glass and the plate side-by-side in the same location (away from direct sun or wind).
6. Have students observe both. Check back every 30 minutes or at the end of the class.

Observation: The water on the plate will evaporate much faster than the water in the glass. 
Conclusion: This shows that a larger surface area increases the rate of evaporation.

Part 2: Demonstrating Wind Speed

1. Measure two equal, small amounts of water (e.g., 20 ml each).
2. Pour one amount onto each of the two identical plates, spreading it evenly.
3. Place one plate in a still part of the classroom.
4. Place the second plate in front of a fan set to a low speed (to simulate wind).
5. Have students observe both plates.

Observation: The water on the plate in front of the fan will evaporate much faster. 
Conclusion: This shows that wind speed (air movement) increases the rate of evaporation.