The dew point is the temperature to which air must be cooled before the water vapor in it condenses. Water vapor condenses on a surface when that surface is colder than the air. For example, when warm breath strikes the cold windshield, water vapor molecules cool, slow down, and join together to form small drops of water.
Condensation is a key component of the water cycle.
Record the air temperature. Measure the temperature of water that is warmer than the air temperature and pour it into the can. Add a slush mixture of crushed ice and salt into the water and slowly stir the mixture with the thermometer, keeping its reservoir in contact with the can's surface. Record the temperature at the precise moment small water drops first appear on the can's exterior. Conduct a classroom discussion on dew-point temperatures.