A puddle on the sidewalk is gone by the afternoon, but nobody mopped it up. What happened to the water?
AThe water was destroyed by the sun
BThe water soaked into the ground and completely disappeared
CThe water evaporated — it turned from liquid into invisible water vapor in the air
DThe water is still there but became invisible on the sidewalk
The water evaporated. Heat from the sun gave the water particles at the surface enough energy to escape into the air as water vapor (gas). The water was not destroyed — it changed state and is now part of the air as invisible gas.
Question 2 True / False
Evaporation can mainly happen when water reaches its boiling point of 100 degrees Celsius.
TTrue
FFalse
Answer: False
False. Evaporation happens at any temperature, as long as some particles at the surface have enough energy to escape into the air. Wet clothes dry at room temperature, and puddles disappear on cool days. Boiling is different — it happens throughout the liquid at 100 degrees Celsius. Evaporation is a surface process that happens well below boiling.
Question 3 Short Answer
Why does a wet towel spread out flat dry faster than the same wet towel bunched up in a ball?
Think about your answer, then reveal below.
Model answer: The flat towel has more surface area exposed to the air, so more water can evaporate at the same time. The bunched-up towel traps wet surfaces against each other where the air cannot reach them.
Evaporation only happens at the surface where liquid meets air. More surface area means more liquid is exposed and can turn into vapor at once. This is why spreading laundry out makes it dry faster.