Understanding Evaporation Rate Lab
Evaporation removes water from an exposed surface even when the water is not boiling. This lab lets you compare conditions that change the modeled rate, then follow the remaining water mass as the experiment runs.
The useful measurement is mass loss over time. Compare the mass at two recorded times and divide the difference by the elapsed time to describe an average rate, keeping the time units consistent throughout your investigation.
Temperature affects the tendency of water to enter the vapor phase. In the simplified model, raising the controlled temperature increases the saturation vapor pressure and increases evaporation when the other settings stay the same.
Relative humidity describes how much water vapor the air contains compared with saturation at that temperature. Lower relative humidity leaves a larger vapor pressure difference between the water surface and the surrounding air, which drives faster modeled mass loss.
At full saturation, the model has no net evaporation. Water molecules can still move between liquid and vapor, but a balanced exchange need not produce a continuing decrease in the amount of liquid water.
Surface area is separate from the amount of water present. A broad shallow container exposes more water to the air than a narrow container, so the lab lets you change the exposed area while starting with the same water mass.
Airflow carries moist air away from the surface and replaces it with surrounding air. Increasing the airflow setting strengthens that effect in this teaching model, but it does not mean air movement supplies unlimited energy for evaporation.
Choose one variable for a fair comparison and keep the others fixed. For example, compare two surface areas at the same temperature, humidity, and airflow, then look for a difference in the slopes of the mass curves.
The seed makes the small modeled trial variation repeatable. Keeping it fixed helps you isolate a deliberate change in conditions, while trying another seed illustrates why separate measurements may not line up perfectly even under similar conditions.
Pause the run when you want to inspect a reading and record a data point. Use the experiment's displayed time rather than the time you spend watching, because the animation advances model time faster than a real drying experiment.
The model holds its conditions constant and assumes the water and air share the controlled temperature. It does not calculate cooling of the water, changing weather, or condensation, and its rate coefficient is an illustrative classroom choice rather than a calibrated drying forecast.
Use your recorded comparison to explain a cause and an observed effect. Identify the setting you changed, cite the mass loss over a stated interval, and describe which model assumption would need reconsideration before applying your result to a puddle, wet clothing, or an outdoor pond.
