"Now hold the slate over the spout of the kettle, while the steam is pouring out. What do you see? The slate is covered with little drops of moisture.
"The vapor in the air leaves little drops of moisture on the sides of the tumbler; the vapor from your breath and the steam from the kettle leave drops of moisture on the slate. The tumbler and the slate were cold.
"It is cold that changes the vapor into drops of moisture. Teacher says the vapor in the air is invisible only because it is split up into such extremely small particles that they cannot be seen.
"Cold causes these tiny particles to rush together, so that they are pressed into a smaller space, and then we can see them. We say they are condensed.
"The steam as it first comes from the spout of the kettle is invisible. But when it meets with the colder air of the room it condenses. The tiny particles of the vapor are made to rush together, and we see it as it floats away.
"We do not usually see our breath as it leaves the mouth and nostrils. But when the weather is very cold, the vapor of the breath condenses and the breath at once becomes visible."SUMMARY