Tossing Hot Water into Frigid Air

Tossing hot water into frigid air is an example of water changing states from liquid to gas (water vapor). In this video, water that has just boiled was tossed into frigid air (air temperature was -15 degrees F, windchill -32 degrees F and the dew point was -20 degrees F). The water was brought to a boil (thermal energy) so the molecules were close to the evaporation point (moving quickly). Hot water evaporates faster than cool water. When the water was tossed into the air, the water separated into smaller water droplets, allowing the frigid air to cool the water more quickly. The air is too cold to hold the water vapor (dry air) so the water condenses, making a cloud.

• What happens to boiling water when you toss it into frigid air? Why?

• When is thermal energy being added and removed during this process?
• Why does boiling water evaporate into frigid air?
• Does the dew point affect the evaporation rate?  
• What would happen if warm water was used instead of boiling water?
• Why does the air temperature have to be very cold?

Students could:

• Observe a similar teacher-lead investigation. Try tossing the boiling water on a variety of days with different temperatures and dew points. Have students record and compare observations.
• Modify investigation with water at different temperatures or different liquids.

• Education.com | Science Project: Evaporate: This page describes the steps for an evaporation experiment.
• PBS LearningMedia | Plum Landing: Evaporation Station: Three sisters paint with water outside on a sunny day and experiment to see how sunlight and shade affect how their water paintings evaporate, in this video from Plum Landing.