In this lab, students will explore the phase change of condensation and determine whether this process is endothermic or exothermic. Students will then investigate how water vapor condenses, what effect surrounding temperature has on the rate of condensation, and what is happening to the molecules when they condense.
This lab will help prepare your students to meet the performance expectations in the following standards:
- Scientific and Engineering Practices:
- Developing and Using Models
- Engaging in Argument from Evidence
By the end of this lab, students should be able to
- Describe that the process of changing matter from a gas to a liquid is called condensation.
- Demonstrate that condensation is a specific kind of thermochemical process.
- Explain how changing the surrounding temperature effects the rate of condensation for a gas.
This lab supports students’ understanding of
- States of Matter
- Phase changes
- Endothermic process
- Exothermic process
- Molecular motion
- Intermolecular forces (specifically hydrogen bonding)
Teacher Preparation: 20 minutes
Lesson: 50 minutes
- 2 pitchers
- Hot water (from the tap or use a warming pot/hot plate to warm up water)
- Ice cubes (one per group)
- 100 mL graduated cylinder
- 2 Small clear plastic cups (per group)
- 2 Wide clear plastic cups (per group)
- Paper towels
- Saucepan/pot with lid
- Hot plate
- Timer (one per group)
- Always wear safety goggles when handling chemicals in the lab.
- Students should wash their hands thoroughly before leaving the lab.
- When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.
- Exercise caution when using a heat source. Hot plates and/or heating devices should be turned off and unplugged as soon as they are no longer needed.
- Be cautious when moving around the heat source. Do not reach over it, tie back hair, and secure loose clothing.
- Warn students about handling the hot tap water, exercise caution, and ensure heat-protective gloves are available for use.
- This lab was originally designed as a lab for elementary and middle school students, called Condensation. This high school version of the lab is a modification, inspired by that resource, as part of the AACT Strategic Plan and the work of the AACT Grade-Level Ambassadors.
- This activity calls for both small and wide clear plastic cups. Be sure the cups fit together, as shown in the picture. The wide cup should be used to hold the warm water and is placed on the bottom. The small cup is turned upside down and placed in the wide mouth cup. They should make a seal together. Be sure that the smaller cup, that will be inverted is completely clear. See photos below for examples:
- You will need a way to warm water for the initial demonstration. I suggest using a saucepan and a single burner. Place the water on the burner/hot plate and wait about 10 minutes before starting the demonstration. (This will be used for students to answer the prelab questions). Leave the lid off to get started. If a single burner/saucepan is not available, consider using a microwave to heat the water or recording the process at home and showing the students a video recording in order to complete the pre-lab demo.
- You will need hot water for the experiment, but please note that it does not and should not be boiling or extremely hot for the experiment portion. Using hot tap water is recommended.
- Depending on what is available in your classroom, students can obtain hot water for the experiment from the tap, or they can use a hotplate or microwave to heat the water. Make sure you have proper heat-protective gloves/oven mittens available for students to use.
- Before you have students start working on the activity, discuss where they believe they have experienced condensation and what their definition of it is. Use examples such as a glass of lemonade during the summer, fogged-up windows in the winter, etc.
- I recommend that students work in groups of 2-3 for the lab.
- During the experiment when students put the ice cube on top of the cup, they should see that the rate of condensation increases due to the temperature decrease outside of the cup.
- An Answer Key document has been provided for teacher reference.
For the Student
During any thermochemical process (like a phase change or a chemical reaction), heat energy is released by the system into the surroundings or absorbed by the system from the surroundings. You will need to think about this from the point of view of the system.
You will be investigating how heat energy is transferred during the process of condensation. You will need to determine whether the phase change is endothermic or exothermic and explain how the molecular movement and the rate of this physical change is affected by varying the surrounding temperature.
To simulate how gas changes to a liquid and how to change the rate of condensation.
- What is an endothermic process?
- What is an exothermic process?
- How is heat energy defined?
- What do we mean by the “system”? What about the “surroundings”?
- What are intermolecular forces, specifically hydrogen bonding?
- How does temperature affect the speed at which molecules can move?
- In front of the room there is a pot of water boiling, what do you think will happen when the pot is covered with a lid?
- Go to the front of the room and ask for the lid to be placed on top of the pot. Watch what happens. Describe what you see:
- Hot tap water
- 100mL graduated cylinder
- Ice cube
- 2 small clear plastic cups
- 2 Wide clear plastic cups
- Magnifying glass
- Paper towels
- Using a 100 mL graduated cylinder, measure 235mL of hot water and pour it into the wide mouth cup.
- Repeat step 1 and add the hot water into the second wide mouth cup.
- Quickly place each of the empty small clear plastic cups upside down on top of the water-filled cups to create a closed container. See the series of photos below for reference.
- Place a piece of ice on top of one of the inverted cups. See photo for reference.
- Start the timer and observe the cups for 2 minutes.
- Use the magnifying glass to look at the sides and top of both inverted cups during the 2 minutes.
- Remove the piece of ice and put it in the sink then take cups apart. Examine the tops of each cup. Record your observations for each cup in the data table below.
- Clean-up as directed by your teacher.
(with ice cube present)
Post-Lab Analysis Questions
- Compare the amount of water on the inside of the top of each cup. Which top cup had more water in it, and how did the ice cube affect the rate of condensation? Be sure to include what was happening to the individual molecules of water in both cups in terms of speed, distance between the particles, and their intermolecular forces.
- Was the process of condensation endothermic or exothermic? Justify your answer in terms of system, surroundings, and heat energy.