Which of these is not considered a pure substance? An atom
A mixture
An element
A compound

A mixture is not a pure substance.

c, liquids evaporate, creating a gas

warm front forms when a moist, warm air mass slides up and over a cold air mass. as the warm air mass rises, it condenses into a broad area of clouds. a warm front brings gentle rain or light snow, followed by warmer, milder weather.

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