Q1
Evaporation increases with:
Ahigher temperature
Bhigher humidity
Clower surface area
Dno wind
CBSEClass 9 (CBSE)ScienceCh 1 · Topic 2
Change of State and Evaporation
Learning how matter changes state and the factors affecting evaporation.
Core concept
The rate of evaporation is influenced by several factors: it increases with higher temperature (more particles have enough energy to escape), larger surface area (more particles exposed to the surface), higher wind speed (removes vapour particles, maintaining a concentration gradient), and lower humidity (more room for vapour in the surrounding air). Evaporation causes cooling of the remaining liquid, since the particles that escape carry away the most kinetic energy, leaving behind lower-energy (cooler) particles — this is why sweating cools the human body.
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• Evaporation is a surface phenomenon occurring at any temperature; boiling occurs throughout the liquid at a fixed temperature.
• Evaporation rate increases with: higher temperature, larger surface area, more wind, lower humidity.
• Evaporation causes cooling because high-energy particles escape, leaving lower-energy particles behind.
• This cooling effect explains why sweating cools the human body.