Consider the following information:

An important effect of heat is that it can produce a change of state. Matter exists in any of the three states–solid, liquid, or gas. In a gas, the particles can move around freely and independently. In a liquid, particle movement is a bit constrained and limited to sliding and flow movement within its volume. In a solid, particle movement is restricted to only vibrational motion of particles in their fixed positions. 

Thus, a change of matter from one physical state to another is called change of state. The state of matter depends on its temperature and the pressure that is exerted on it. 

There are six distinct changes of phase that happen to different substances at different temperatures: 

• Freezing – A substance changes from a liquid to a solid. 

• Melting – A substance changes from a solid to a liquid. 

• Condensation – A substance changes from a gas to a liquid. 

• Evaporation or vaporization – A substance changes from a liquid to a gas.

• Sublimation – A substance changes directly from a solid to a gas without going through the liquid state. 

• Deposition – A substance changes directly from a gas to a solid without going through the liquid state.
In warm, humid weather, people who wear glasses experience a very common effect of phase change while getting off an air-conditioned bus: their glasses suddenly fog up. After a while, the glasses become clear again. Which of the following physical processes are involved in these phenomena?

A. condensation followed by evaporation

Explanation

For the first few seconds, the temperature outside of the airconditioned bus is greater than the temperature of the glass that was still at the same temperature as the inside of the air-conditioned bus. Thus the water vapor in the surrounding air condenses to form small water droplets that make the glass fog. As the temperature of the glass increases to match the outside temperature, the water droplets evaporate and the glass becomes clear again. Choice A is correct

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