Lesson Summary Students observe and reflect on a whole class demonstration in which the teacher places two paper towels that have been soaked with equal amounts of water out to evaporate. One of the towels is left in a cup with a lid and the other is placed in an open cup. Teacher Background Evaporation is the process by which liquid water turns into water vapor, a gas. The rate of evaporation depends on four conditions: humidity, temperature, surface area exposed to the air, and air movement over the surface. More evaporation will take place when the air is dry, when temperatures are high, when the surface of the water if large and when winds are blowing over the water. This demonstration lesson is meant to be a shared reference point. By comparing the two cups before, during and after evaporation, students conclude that water escapes into the air. Set-up/Management Tips This part will take two sessions of 10-15 minutes on two consecutive days, or you could complete the first session early in the morning and the second part at the end of the day. Consider your climate for this activity. If you have high levels of humidity, it will take longer for the towel to dry out Literacy Support Books Available Through VAST Mediagraphies (see Literacy Links) Science Stories Read “Wet and Dry Places.” Scientific Vocabulary The following words are key vocabulary words that will be introduced in this lesson and reinforced throughout the unit: evaporate                                    water vapor