The Disappearing Act
The Disappearing Act is a Grade 5 science concept from Amplify Science (California) introducing evaporation — the process by which liquid water absorbs heat and transforms into invisible water vapor gas. When a puddle dries up on a hot day, the water hasn't vanished; it changed state and rose into the air. Covered in Chapter 2, this concept is the entry point for understanding the water cycle: evaporation is the mechanism that moves water from Earth's surface into the atmosphere, setting up all subsequent precipitation.
Key Concepts
Have you ever seen a puddle dry up on a hot day? The water didn't just vanish into nothingness. It changed form.
When liquid water warms up, it turns into a gas. This process is called evaporation . The liquid water becomes water vapor , an invisible gas that rises and mixes with the air. The water is still there; you just can't see it anymore.
Common Questions
What is evaporation?
Evaporation is the process by which liquid water transforms into water vapor (gas) when it absorbs heat energy. The water molecules gain enough energy to break free from the liquid and escape into the air as invisible gas. This is why puddles, wet sidewalks, and damp clothes eventually dry up.
Where does the water go when a puddle dries up?
When a puddle dries up, the water molecules evaporate into the air as invisible water vapor. The water hasn't disappeared — it changed from liquid to gas and is now floating in the atmosphere. This same water will eventually cool and condense into clouds and rain elsewhere.
What is the difference between evaporation and boiling?
Both convert liquid water to vapor, but evaporation occurs at the water's surface at any temperature and is a slow process. Boiling occurs throughout the liquid at 100°C and is much faster. On a warm sunny day, a puddle evaporates without ever reaching boiling temperature.
What causes water to evaporate faster?
Water evaporates faster when temperature is higher, wind is blowing, the surface area is greater, and humidity is lower. Wet clothes dry faster on a hot, windy day than in a closed, humid room.
When do 5th graders learn about evaporation?
Evaporation is introduced in 5th grade science. Amplify Science California Grade 5 Chapter 2 covers evaporation as part of the investigation into why more rain forms over West Ferris, tracing how water gets into the atmosphere in the first place.
Is evaporation a physical or chemical change?
Evaporation is a physical change. The water molecules (H₂O) do not change their chemical structure — they simply change from liquid state to gas state. No new substances are formed; the same water molecules that were liquid are now in the air as vapor.
Which textbook introduces evaporation for 5th grade science?
Amplify Science (California) Grade 5 Chapter 2 introduces evaporation as the first step in understanding how water enters the atmosphere, leading to the investigation of regional precipitation differences.