Melting, boiling and evaporation
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What this model shows
Each run lasts 5 minutes in a real lab, shown here in about 16 seconds. The thermometers are read to the nearest 0.5 °C and the balances to 0.01 g, every 30 s, as you would read real ones.
The readings follow a simple model. Energy passes from each tube’s hot water into its towel, and from the towel into the air, faster with the fan. Water evaporates from towel B faster when the towel is warmer, when more of it is open to the air and when the air moves, and the water that evaporates takes energy from the towel. The model shows the pattern, not exact values for a real towel.
The dry towel is only a rough comparison: a wet towel also passes energy from the tube more easily, and its water starts at room temperature. The balance is the evidence that water evaporated.
The magnifier is a model too: a few particles stand for billions of billions, drawn far bigger than real, and their speeds are exaggerated. Water that leaves the view is made up from the rest of the towel.
With reduced motion each step is drawn complete at once and the magnifier shows a still picture.
Select equipment to read its description in the card.