Which of the following is not a phase change?

melting of snow
evaporation of water from the ocean
condensation of water vapor to form clouds
hydrogen and oxygen gas combining to form water vapor

Question

Which of the following is not a phase change?

melting of snow
evaporation of water from the ocean
condensation of water vapor to form clouds
hydrogen and oxygen gas combining to form water vapor

Vocaloid · Answer

a phase change is a process by which a substance changes its state of matter (solid, liquid, gas, etc) but still retains the same chemical composition. that being said, which one do you think doesn't fit this description?