# Question Video: Evaporation and Condensation Physics • 9th Grade

Fill in the blanks: Condensation is the process in which particles in a ＿ combine into liquid droplets suspended in it. If the ＿ of the condensed droplets is considerably greater than that of the ＿, the droplets will fall downward. [A] gas, density, gas [B] gas, speed, gas [C] liquid, altitude, liquid [D] gas, temperature, liquid

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### Video Transcript

Fill in the blanks: Condensation is the process in which particles in a blank combine into liquid droplets suspended in it. If the blank of the condensed droplets is considerably greater than that of the blank, the droplets will fall downward.

We see we’re given four possibilities for answer options, that is, words to fill in these blanks in the sentence. To figure out which choice is best, let’s reconsider the sentence with blanks in it.

It starts out “Condensation is the process in which particles in a blank combine into liquid droplets suspended in it.” We can understand from the fact that particles are combining into suspended liquid droplets that these droplets must be suspended in a state of matter different from liquid.

After all, if the state of matter that when in our blank was liquid, there’d be no way to differentiate these combined condensed liquid droplets from the rest of the liquid. The fact that the droplets are separate from the rest means that the rest must be nonliquid.

Indeed, condensation involves particles in a gas combining into liquid droplets. That fills in the first section of our sentence.

In the next blank, we’re considering some property of the condensed droplets that can be considerably greater than that of what we now know to be a gas. With our third blank filled in, we now want to know just what property of these condensed droplets would it be that if it was greater than those of the gas would cause the droplets to fall downward.

Well, if the droplets were more dense than a gas, that would have that effect. If we put in the word density into our second blank, then our sentence now reads this: “Condensation is the process in which particles in a gas combine into liquid droplets suspended in it. If the density of the condensed droplets is considerably greater than that of the gas, the droplets will fall downward.”

If you’ve ever taken a cold drink outside on a hot humid summer day, you’ve probably seen condensation in action. Water vapor begins to combine into liquid droplets on the side of the cold glass. And of course, if the droplets get big enough, they’ll slide down the glass. And we’ll see their water trails left behind them.

It’s answer choice A that gives us the right words for filling in the blanks in the sentence. This is how condensation works.