See the science

Condensation

Condensation is the reverse: water vapour becomes liquid again.

What is happening?

When moist air cools, some of its water vapour can turn into tiny droplets.

Where do we see it?

That is what happens on a cold bottle. The water outside has not passed through the glass; it comes from the surrounding air.

Clouds also form through condensation, when tiny droplets or ice crystals appear in the atmosphere.

Worth rememberingThe drops on a cold glass come from the air around it.

One important point

Condensation depends on how much water vapour the air contains and on temperature. Humid air reaches droplet-forming conditions more easily.

Go one step further

A useful way to understand this phenomenon is to separate the driving force from the visible result. Temperature, pressure, concentration, surface area and the nature of the materials can each change the rate or the final state. In real systems, several of these factors often act at the same time.

That is why the same phenomenon can look different in a laboratory, in the kitchen or outdoors. The underlying chemistry or physics stays the same, but the conditions change the balance.

What changes in practice

Real examples often add one more layer: geometry, impurities, coatings, humidity, flow or manufacturing history can alter what you observe even when the main mechanism is unchanged.

That is why two objects made from broadly similar materials can behave differently. The useful question is not only “what is it made of?” but also “how is it built, under what conditions, and for which function?”