Evaporative Cooling with Liquids

This activity demonstrates how evaporation causes cooling by comparing how water and rubbing alcohol feel when placed on the skin. As the liquids evaporate, they remove heat from the surface, showing how sweating helps regulate body temperature.

1. Prepare one cup with a tablespoon of water and another with a tablespoon of rubbing alcohol.
2. Use a pipet to place a few drops of water on the back of your hand and spread it with your fingers.
3. Blow gently over the damp skin and note any temperature changes or sensations.
4. Rinse the pipet, then use it to place a few drops of rubbing alcohol on the back of your other hand.
5. Spread the alcohol and blow gently over it. Compare the sensation to the water.
6. Record which liquid produced a greater cooling effect.

Cooling by Evaporation Activity - Homemade Science with Bruce Yeany:

📄 Evaporative Cooling with Liquids - Science Buddies: https://www.sciencebuddies.org/stem-activities/evaporative-cooling-with-liquids

• Compare evaporation rates of alcohol and water by placing equal amounts in cups in the sun and monitoring how long they take to evaporate.

• Do not ingest rubbing alcohol.
• Avoid contact with eyes or open cuts.
• Wash hands thoroughly after the experiment.
• Dispose of unused rubbing alcohol by flushing it down the sink with plenty of water.
• Conduct the experiment in a ventilated area.

• Why does alcohol feel colder than water when it evaporates? (Because alcohol evaporates faster due to its lower boiling point, it removes heat from the skin more quickly.)
• How does blowing on the liquid affect evaporation? (It increases airflow, which speeds up evaporation and enhances cooling.)
• Why does sweating help regulate body temperature? (Sweat absorbs body heat during evaporation, carrying it away and cooling the body.)
• Which environmental factors influence evaporation rates? (Temperature, airflow, surface area, and the type of liquid.)