Condensation

A day or two before the lesson begins, ask the students the question:
It is the middle of the summer and you want to go outside. You take an ice cold drink outside and sit it on table while you run back in to grab something. When you return outside, there are drops of water all over the outside of your drink. Where did this water come from?
There will probably be many different answers. Some kids might say that the drink was “sweating” or the water melted, or it was the ice out of their drink. A few students may answer condensation, but the students must have enough background knowledge of water vapor and thermal energy to really grasp a deeper understanding of condensation through the activity during this lesson. 

Day 1:
1. Ask the students to clean off their desks and focus their eyes on you.
2. Linking prior knowledge to what the students may already know about condensation, ask the students similar questions to the one you asked prior to the day of the lesson about their experiences with condensation using questions such as the following: You may have made a cold window “cloudy” by breathing on it and then drawn on the window with your finger. Where do you think that cloudiness comes from?
3. Have them turn and talk with their partner about where they think the tiny droplets of water in a cloud come from. Call on people to answer. Help students realize that the moisture in all of these examples came from water vapor in the air.

Lesson Procedures:
1.      Begin by telling students that they will be working in groups today and that they will need to follow directions very carefully.

2.       Begin explaining to them (not in much detail) the process of the lab they will be completing. You will say:

“When you get in your assigned group that I will be assigning through class Dojo (or however you assign groups), please pick a person for each of the following jobs: material gatherer, sink goer for water, and idea writer. Once you have assigned these jobs, sit quietly with your thumb raised.”

 The procedures are as follows:

-          Fill a wide clear plastic cup about 2/3 full of hot tap water. Place a taller clear plastic cup (with a smaller rim) over the top as shown.

-          Watch the cups for 1–2 minutes.

-          Use a magnifier to look at the sides and top of the top cup.

-          Take the top cup off and feel the inside surface.

3.      Have the materials laid on the front table and begin pouring their water into cups. The class will then begin the procedures together as you remind the idea writer to write down observations he/she hears their group members say aloud.

4.      As the students are finishing up with their observations, ask some of the following questions, asking them to talk with their group before answering aloud. Call on random groups.

-          What do you notice about the top cup?

-          What do you think is on the inside of the top cup?

-          How do you think the water droplets in the top cup got there?

5.       Then explain to students that as water vapor moves away from the hot water it cools. It also cools when it comes in contact with the inside surface of the top cup. When the water vapor cools enough, it changes state, becoming tiny drops of liquid water. The process of changing from a gas to a liquid is called condensation.

6.       The last part of the day will consist of them coming up with a group consensus as to whether or not they believe cooling water vapor increases the rate of condensation. Go around and gather “yes” or “no” answers from each group and tally them on the board.

Day Two
 

1. Begin by telling students that they will be working in groups again today and that they will need to follow directions very carefully. Remind them of the question asked yesterday.
2. Begin explaining to them (not in much detail) the process of the lab they will be completing. You will say:

“Today we will be experimenting to see if cooling water vapor increases the rate of condensation. Let’s take a look at the data we collected yesterday from each group to see what we think the answer may be. Today, your group jobs will remain the same so please remember what your job was. Today the material gatherer needs to grab a worksheet as well. You will use this to draw your observations.”
 
The procedures are as follows:

• Fill two wide clear plastic cups about 2/3 full of hot tap water.
• Quickly place taller clear plastic cups (with smaller rims) upside down on each cup, as shown.
• Place a piece of ice on top of one of the cups.
• Wait 2–3 minutes.
• Remove the ice and dry the place where the ice was with a paper towel.
• Use a magnifier to examine the tops of the two upper cups.

 
3. Tell the class to take a close look at their two cups and draw on their worksheets what they see. The students will work as a group during the part of the lab as well. The cups will already be drawn on the paper for them.
4. Once you see they are finishing up, ask the following questions and they will discuss with their group before answering aloud like the previous day:

• Which top cup appears to have more water on it?
• What does the amount of water have to do with the rate of condensation?
• Does cooling water vapor increase the rate of condensation

5. As students seem to be finishing up with their drawings and you go over the questions asked after the second part of the lab, you will do more of explaining.

Teacher: When water is heated, it turns into its gas form, called water vapor – which we have talked about multiple times thus far. This is what happens when you see steam rising from a pot of boiling water. When water vapor is cooled, the opposite happens: The water vapor turns back into a liquid. As we know, the air is full of water vapor. So, when that water vapor hits the cold glass holding your drink that we talked about earlier, the molecules of the water vapor slow down and change states from gas to liquid. They gather together causing condensation and form into the tiny little droplets of water rolling down your cup.

At the end of the lesson, ask the same question you asked in the beginning about the mystery water on the cup. This should help you check for understanding. 
 

Have students turn in worksheet for a grade.

Grade participation and cooperation during the labs.