Water Can Change State Over and Over Again

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Lesson two.3

Changing State: Condensation

Key Concepts

• Condensation is the process in which molecules of a gas slow down, come up together, and form a liquid.
• When gas molecules transfer their energy to something libation, they slow downwardly and their attractions cause them to bond to become a liquid.
• Making water vapor colder increases the rate of condensation.
• Increasing the concentration of water vapor in the air increases the rate of condensation.

Summary

Students investigate the condensation of water vapor on the within of a plastic cup. Then they design an experiment to meet if cooling water vapor fifty-fifty more affects the rate of condensation. Students also relate evaporation and condensation to the water wheel.

Objective

Students will be able to depict on the molecular level how cooling water vapor causes condensation. Students will also draw the roles evaporation and condensation play in the water bicycle.

Evaluation

Download the pupil activeness sheet, and distribute one per student when specified in the activity. The action sheet will serve every bit the "Evaluate" component of each 5-E lesson programme.

Prophylactic

Brand sure you and your students wear properly fitting goggles.

Materials for Each Group

• 1 short wide-rimmed articulate plastic cup
• one tall smaller-rimmed clear plastic cup
• Hot water (about 50 °C)
• Magnifier

Materials for the Demonstration

• 2 clear plastic cups
• Room-temperature water
• Ice cubes
• Gallon-size zero-closing plastic bag

About this Lesson

Effort the demonstration before presenting it to your students because it volition not work if the humidity is likewise low. You could instead show students the video Condensation on a Common cold Cup. The activity for the students will piece of work no affair how dry out or humid the air.

1. Gear up for the demonstration about 5–x minutes before grade.

   Materials for the demonstration

   • 2 articulate plastic cups
   • Room-temperature water
   • Water ice cubes
   • Gallon-size zilch-closing plastic purse

   Procedure

   1. Place water and water ice cubes into ii identical plastic cups.

   2. Immediately place i of the cups in a zip-endmost plastic pocketbook and get equally much air out of the bag every bit possible. Close the handbag securely.

      
   3. Allow the cups to sit down undisturbed for nearly v–x minutes.

   Expected results

   The cup inside the pocketbook should have very little moisture on information technology considering non much water vapor from the air was able to contact it. The cup exposed to air should have more than wet on the outside because it was exposed to the water vapor in the air, which condensed on the outside of the cup.

2. Show students the two cold cups of water and ask why water appears on the outside of merely one of them.

   Bear witness students the two cups you prepared and ask:

   Which loving cup has the nearly moisture on the outside of it?

   Students should realize that the cup exposed to more air has the most moisture on the exterior of it.

   Why do yous retrieve the cup that is exposed to more air has more water on the outside of it?

   Make sure students empathise that this moisture came from water vapor in the air that condensed on the outside of the cup. Remind students that water vapor is ane of the gases that makes up air. The loving cup in the bag has very little to no wet on it because it is exposed to much less air. Less air means less water vapor.

   Some people recollect that the moisture that appears on the exterior of a cold loving cup is water that has leaked through the cup. How does this demonstration prove that this idea is not true?

   Considering in that location is piddling to no moisture on the outside of the cup in the bag, students should conclude that h2o could non take leaked through the cup. If the moisture came from leaking, at that place would be water on the outside of both cups.

3. Innovate the process of condensation.

   If students exercise not know what the process of condensation is, you lot can tell them it is the opposite of evaporation. In evaporation, a liquid (similar water) changes state to get a gas (water vapor). In condensation, a gas (like h2o vapor) changes land to become a liquid (water).

   Explain that as h2o molecules in the air cool and irksome down, their attractions overcome their speed and they join together, forming liquid water. This is the procedure of condensation.

   Ask students:

   What are some examples of condensation?

   Coming up with examples of condensation is a bit harder than examples of evaporation. One common instance is water that forms on the outside of a cold cup or the moisture that forms on machine windows during a absurd nighttime. Other examples of condensation are dew, fog, clouds, and the fog you run across when yous breathe out on a cold day.

   Y'all may take made a cold window "cloudy" by breathing on it and so fatigued on the window with your finger. Where do yous recollect that cloudiness comes from?

   Aid students realize that the wet on the window, and all of the examples of condensation they gave, comes from h2o vapor in the air.

   A real deject is made upwards of tiny droplets of water. Where do you lot recall they come from?

   The h2o in a deject comes from water vapor in the air that has condensed.

   Requite each student an activity sheet.

   Have students answer questions about the demonstration on the activeness canvas. They will also record their observations and respond questions virtually the activity. The Explain It with Atoms & Molecules and Take It Further sections of the activeness sheet will either exist completed every bit a class, in groups, or individually depending on your instructions. Wait at the teacher version of the activity sheet to observe the questions and answers.

4. Have students collect a sample of water vapor and observe the process of condensation.

   Question to investigate

   What happens when water vapor condenses?

   Materials for each group

   • 1 short wide-rimmed clear plastic cup
   • 1 alpine smaller-rimmed clear plastic cup
   • Hot water (about l °C)
   • Magnifier

   Process

   1. Fill a broad clear plastic cup nigh ⅔ total of hot tap water. Place the tall loving cup upside downward within the rim of the bottom cup as shown.

      
   2. Lookout the cups for 1–2 minutes.
   3. Utilise a magnifier to look at the sides and top of the top cup.
   4. Take the top cup off and experience the inside surface.

   Expected results

   The acme cup will become cloudy-looking equally tiny drops of liquid water collect on the within surface of the cup.

5. Discuss with students what they think is happening within the cups.

   Enquire students:

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

   Students should agree that the inside of the elevation cup is coated with tiny drops of liquid water.

   How do you remember the drops of water on the inside of the pinnacle cup got at that place?

   Students should realize that some of the h2o in the cup evaporated, filling the inside of the top loving cup with invisible water vapor. Some of this water vapor condensed into tiny drops of liquid water when it condensed on the within of the tiptop cup.

   Explain that water vapor leaves the hot h2o and fills the infinite above, contacting the inside surface of the superlative cup. Energy is transferred from the water vapor to the cup, which cools the h2o vapor. When the water vapor cools enough, the attractions betwixt the molecules bring them together. This causes the water vapor to modify land and go tiny drops of liquid h2o. The process of changing from a gas to a liquid is chosen condensation.

6. Testify an animation to help students understand what happens when gases condense to their liquid land.

   Show the blitheness Condensation.

   Explain that the fast-moving molecules of water vapor transfer their free energy to the side of the cup, which is cooler. This causes the water vapor molecules to slow downwardly. When they slow downward enough, their attractions overcome their speed and they stay together every bit liquid h2o on the inside surface of the cup.

7. Discuss how to design an experiment to find out whether increased cooling of the water vapor affects the charge per unit of condensation.

   The goal of this discussion is to help students meliorate sympathise the experimental pattern outlined in the procedure.

   Enquire students:

   How could we prepare an experiment to encounter if making water vapor fifty-fifty colder affects the rate of condensation?

   How can we become the h2o vapor we need for this experiment?

   Students may suggest collecting h2o vapor as in the previous activity or collecting information technology over a pot of humid water or some other way.

   Will nosotros need more than than ane sample of water vapor? Should we cool one sample of water vapor, but non the other?

   Assistance students empathize that they volition need 2 samples of water vapor, but one of which is cooled.

   How will we cool the water vapor?

   Students may have many ideas for cooling h2o vapor, like placing a sample in a fridge or cooler filled with ice, or placing a sample of water vapor outside if the weather condition is cool plenty.

   How will you know which sample of water vapor condensed faster?

   Past comparing the size of the drops of water formed in both samples, students tin can make up one's mind whether cooling water vapor increases the rate of condensation.

8. Have students practise an activity to find out whether cooling water vapor increases the rate of condensation.

   Read more than most evaporation and condensation in the instructor groundwork department.

   Question to investigate

   Does making water vapor colder increase the charge per unit of condensation?

   Materials for each group

   • 2 short wide-rimmed clear plastic cups
   • 2 tall smaller-rimmed clear plastic cups
   • Hot water (about 50 °C)
   • Magnifier
   • Water ice

   Procedure

   1. Fill two wide clear plastic cups nearly ⅔ full of hot tap water.
   2. Quickly place the taller cups upside down inside the rim of each cup of h2o, as shown.

   3. Identify a piece of ice on acme of one of the cups.

      
   4. Await two–iii minutes.
   5. Remove the ice and apply a paper towel to dry out the top of the cup where the water ice may take melted a fleck.
   6. Use a magnifier to examine the tops of the two upper cups.

   Expected results

   There volition be bigger drops of h2o on the inside of the height cup below the water ice.

9. While waiting for results, take students predict whether increased cooling volition increase the rate of condensation.

   Enquire students to make a prediction:

   • What effect do y'all retrieve adding the ice cube will have on the charge per unit of condensation?
   • Explain on the molecular level, why y'all remember extra cooling might affect the rate of condensation.

10. Discuss students' observations and draw conclusions.

    Enquire students:

    Which peak loving cup appears to have more water on information technology?

    The cup with the ice.

    Why practise you recollect the cup with the ice has bigger drops of water on the inside than the cup without water ice?

    When the h2o vapor is cooled by the ice, the h2o molecules tedious down more than than in the cup without the ice. This allows their attractions to bring more molecules together to become liquid water.

    Does cooling h2o vapor increase the rate of condensation?

    Yes.

    What evidence do you have from the activity to back up your respond?

    Students should realize that the bigger drops of water on the tiptop cup with the ice indicate a greater amount of condensation. Because the water vapor in both sets of cups was condensing for the aforementioned length of time, the water vapor in the cup with the bigger drops must accept condensed at a faster rate.

11. Explicate examples of condensation on the molecular level.

    Inquire students:

    Fogging up a cold window

    When yous exhale out, there is water vapor in your breath. When you breathe on a cold window in the winter, the window gets tiny aerosol of moisture on it or "fogs up." What happens to the molecules of water vapor every bit they get near the cold window?

    The water molecules in your breath are the gas water vapor. They slow downwards as they transfer some of their free energy to the cold window. The attractions between the slower-moving water vapor molecules bring them together to grade tiny aerosol of liquid h2o.

    Warm breath in common cold air

    When you breathe out in the winter, you see "smoke," which is actually a fog of tiny aerosol of liquid water. What happens to the molecules of h2o vapor from your breath when they striking the common cold air?

    The water vapor in your jiff is warmer than the outside air. The water vapor molecules transfer energy to the colder air. This makes the water vapor molecules move more slowly. Their attractions overcome their motion and they join together or condense to form liquid water.

    Evaporation and condensation in the water bicycle

    One common place you see the results of evaporation and condensation is in the weather. Water vapor in the air (humidity), clouds, and rain are all the result of evaporation and condensation. What happens to the water molecules during the evaporation and condensation stages of the h2o cycle?

    Energy from the sun causes water to evaporate from the state and from bodies of water. Equally this h2o vapor moves high into the air, the surrounding air cools it, causing it to condense and class clouds. The tiny aerosol of water in clouds collect on $.25 of dust in the air. When these drops of water go heavy plenty, they fall to the ground equally rain (or hail or snow). The rain flows over the land towards bodies of water, where it can evaporate again and go along the cycle.

    Projection the image Water Bike.

12. Introduce the idea that the corporeality of h2o vapor in the air affects the rate of condensation.

    Ask students if they know what a terrarium is. Tell students that a terrarium is a closed container with moss or other plants in which h2o that continually evaporates and condenses. At first, the evaporation rate is higher than the rate of condensation. Merely every bit the concentration of water molecules increases in the container, the rate of condensation increases. Eventually, the rate of condensation equals the rate of evaporation and the water molecules become back and forth betwixt the liquid and the gas.

    Read more about evaporation and condensation equilibrium in the teacher background department.

    Projection the animation Evaporation and Condensation

    Explain that the animation moves up through a sample of water to the surface. H2o molecules evaporate (leave the liquid) and condense (reenter the liquid) at the same time. The animation shows the beginning of the process where water molecules evaporate at a faster rate than they condense. Explain to students that if the process were to continue, the rate of evaporation and condensation would become equal.

    And so temperature isn't the only factor that affects condensation. The concentration of h2o molecules in the air is also an important factor. The higher the concentration of water molecules in the air (humidity), the higher the rate of condensation.

    This is why clothes dry more than slowly on a humid day. The high concentration of water vapor in the air causes water to condense on the clothes. So fifty-fifty though h2o is evaporating from the apparel, information technology is also condensing on them and slowing down the drying.

13. Take students pattern an activeness to see why wind helps things dry more quickly.

    Explain to students that when water evaporates from something like a paper towel, the area in the air immediately above the newspaper towel has a little extra water vapor in it from the evaporating h2o. Some of this water vapor condenses back onto the paper so the newspaper doesn"t dry every bit quickly. If that water vapor is blown away by moving air like wind, there will be less condensation and the paper volition dry more chop-chop.

    Ask students:

    • How would you design an experiment that can test whether a paper towel dries more apace if the air around the paper towel is moving?

    As you lot heed to suggestions from students, be sure that they identify and control variables. The paper should exist in the aforementioned situation except for air moving over one piece but not the other. It is non a good idea to blow on one because the breath could exist a different temperature than the surrounding air and also contains water vapor. These are both variables that would bear on the experiment. It is better to moving ridge one of the newspaper towels back and along for a few minutes and have someone else hold the other or tape it so information technology hangs freely.

    Materials

    • 2 pieces of brown paper towel
    • Water
    • Dropper

    Procedure

    1. Place one drop of water on ii pieces of brown paper towel.
    2. Accept your partner hold ane while paper while yous swing the other one through the air.
    3. Later on about thirty seconds compare the paper towels to run into if you tin can see any difference in how wet or dry the papers are.
    4. Repeat step 3 until y'all notice a divergence betwixt the moisture spots on the paper towel.

    Expected results

    The water on the paper towel with more air moving over it should dry faster than the other paper towel on the table. The newspaper towel on the table had air with a lilliputian more humidity over it condensing dorsum onto the paper. This slowed downwardly the drying process. The paper waved in the air didn't take humid air around it and condensing dorsum on it as much so information technology dried more chop-chop.

14. Apply the processes of evaporation and condensation to purify water.

    Evaporation and condensation tin can be used to purify water. Imagine what might happen if colored water evaporates and then condenses.

    Question to investigate

    If colored h2o evaporates and condenses, will there exist any colour in the water that is produced?

    Materials for each group

    • 1 brusk wide-rimmed clear plastic loving cup
    • i tall smaller-rimmed clear plastic cup
    • Hot h2o
    • Food coloring
    • Ice cube
    • White napkin or paper towel

    Process

    1. Add hot tap h2o to a wide articulate plastic cup until it is about ⅔ full.
    2. Add 1 drib of food coloring and stir until the h2o is completely colored.

    3. Turn another clear plastic loving cup upside downwards on the loving cup of hot water every bit shown. Place an water ice cube on the tiptop cup to make condensation happen faster.

       
    4. Wait one–3 minutes for water vapor to condense to liquid water on the inside surface of the summit cup.
    5. Use a white paper towel to wipe the inside of the cup to cheque for whatsoever color.

    Expected results

    The h2o that collects on the inside of the tiptop cup will be colorless. The colour will remain in the bottom cup.

    Explain that the procedure described in the process is called distillation. During distillation, h2o that has substances dissolved in it can be purified (as long equally these substances don't easily evaporate). When the water evaporates and condenses, the nutrient coloring is left behind and the pure water tin be collected and used.

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Source: https://www.middleschoolchemistry.com/lessonplans/chapter2/lesson3

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