Evaporative Cooling: Investigating the Effect of Wet vs. Dry Cloths on Surface Temperature
Science Lab · Grade 7
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Type
science_lab
Pre Lab
Background: Have you ever stepped out of a swimming pool on a hot day and felt a sudden chill, even when the air temperature was very warm? That sensation is caused by **evaporative cooling** — a process in which liquid water absorbs thermal energy from a surface as it changes into water vapor and escapes into the air. This is one of the most important ways that **energy transfer** happens in nature and in our own bodies.
When water evaporates, individual water molecules near the surface gain enough energy to break free and become a gas. The energy those molecules carry away comes directly from the surface they were touching, which means that surface loses thermal energy and its **temperature** drops. The faster water evaporates — which depends on factors like air movement, humidity, and surface area — the more quickly a surface cools. This is exactly why sweating cools your body: as sweat evaporates from your skin, it removes heat and lowers your skin temperature.
In this investigation, you will design your own experiment to test whether a wet cloth cools a surface faster than a dry cloth. You will identify your **independent variable** (the factor you intentionally change), your **dependent variable** (the temperature change you measure), and your **controlled variables** (all the factors you keep the same so your results are fair). By collecting and analyzing temperature data over time, you will build evidence to explain how evaporative cooling transfers energy from one place to another.
Vocabulary
Term: evaporative cooling
Definition: The process by which a surface loses thermal energy as liquid water on that surface absorbs energy and evaporates (turns into water vapor).
Term: temperature
Lab Type
Post Lab
Standards
Safety Level
Teacher Notes
Estimated Time
Experiment Design
Research Question
Learning Objectives
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