Lesson 53: Evaporation
Evaporation changes liquid water into water vapor at its surface. This lesson examines how temperature, surface area, airflow, and humidity affect the process and how controlled comparisons help test those effects.
Key Ideas
- Water does not disappear when a puddle dries. It changes into water vapor and moves into the air.
- Evaporation is liquid water changing into invisible gas at its surface. Condensation can change the vapor back into liquid.
- Water molecules stay water molecules during evaporation. They spread farther apart as they become gas.
- Warmth, moving air, drier air, and a larger exposed surface can help water evaporate faster.
- A fair comparison helps us find what affects evaporation. Changing one condition at a time makes the results easier to understand.
Vocabulary
- Evaporation: Liquid changing into gas at its surface.
- Water Vapor: Water in the gas state, which is invisible.
- Molecule: A group of two or more atoms joined together.
- Surface Area: How much of a surface is exposed, such as the top of water in a dish.
- Humidity: The amount of water vapor in the air.
- Variable: Something that can change in a test, such as temperature or the size of a dish.
Discussion Questions
- Getting out of a pool on a breezy day makes you feel cold even when the air is warm. Using what you know about evaporation and energy, why?
- You need to dry a soaked sleeping bag as fast as possible with no dryer. What three things would you do, and which of the three matters most?
- The oceans have been evaporating for millions of years under the sun. Why are they not empty?
Supplies
- A measuring cup, water, a jar with a lid, a soda bottle, a small bowl, and a dinner plate
- Two identical dinner plates, a measuring cup, water, and a sunny windowsill