Which phase change involves a substance changing from a gas to a liquid?

The phase change that involves a substance transitioning from a gas to a liquid is known as condensation. This process occurs when gas molecules lose energy, typically due to a decrease in temperature or an increase in pressure, allowing them to come together and form a liquid.

In practical terms, when the air cools down and can no longer hold all the water vapor it contains, that vapor condenses into tiny droplets of water, which is why you might see dew on grass in the morning or water droplets on a cold beverage. This is a key concept in refrigeration and HVAC systems, where understanding how gases condense into liquids is essential for effectively controlling temperature and humidity within living and working environments.

Other terms like evaporation refer to the transition from liquid to gas, freezing describes the change from liquid to solid, and sublimation involves a direct change from solid to gas, thus they do not apply to the gas-to-liquid transformation described in this question.