Relative Humidity of a Sealed Flask of Air Can Be Changed by Changing the Air's Temperature or by

Are you loving this? Not loving this? Please consider taking a moment to share your feedback with united states of america. Thanks!

Lesson 2.three

Changing Country: Condensation

Key Concepts

• Condensation is the process in which molecules of a gas slow downward, come up together, and class a liquid.
• When gas molecules transfer their energy to something cooler, they boring downwards and their attractions crusade 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 charge per unit of condensation.

Summary

Students investigate the condensation of water vapor on the inside of a plastic cup. So they design an experiment to see if cooling water vapor even more than affects the rate of condensation. Students also relate evaporation and condensation to the h2o bicycle.

Objective

Students volition exist able to depict on the molecular level how cooling water vapor causes condensation. Students volition as well describe the roles evaporation and condensation play in the water wheel.

Evaluation

Download the student activity sail, and distribute one per pupil when specified in the activity. The activeness canvass volition serve as the "Evaluate" component of each 5-E lesson programme.

Safety

Brand sure you lot and your students wear properly plumbing equipment goggles.

Materials for Each Group

• 1 short broad-rimmed clear plastic cup
• ane tall smaller-rimmed clear plastic loving cup
• Hot water (virtually 50 °C)
• Magnifier

Materials for the Sit-in

• two articulate plastic cups
• Room-temperature water
• Ice cubes
• Gallon-size zero-closing plastic bag

Well-nigh this Lesson

Try the demonstration earlier presenting information technology to your students considering it will non work if the humidity is too low. Yous could instead show students the video Condensation on a Cold Loving cup. The activity for the students volition piece of work no affair how dry or humid the air.

1. Prepare for the demonstration almost five–10 minutes before class.

   Materials for the demonstration

   • 2 articulate plastic cups
   • Room-temperature water
   • Water ice cubes
   • Gallon-size zip-closing plastic handbag

   Procedure

   1. Identify water and water ice cubes into two identical plastic cups.

   2. Immediately place one of the cups in a cipher-endmost plastic bag and go as much air out of the handbag as possible. Close the bag deeply.

      
   3. Allow the cups to sit undisturbed for nearly 5–x minutes.

   Expected results

   The cup within the purse should have very footling moisture on it considering non much water vapor from the air was able to contact information technology. The cup exposed to air should have more moisture on the outside considering it was exposed to the water vapor in the air, which condensed on the exterior of the cup.

2. Show students the ii common cold cups of water and ask why h2o appears on the outside of only one of them.

   Show students the two cups you prepared and enquire:

   Which loving cup has the almost wet on the outside of it?

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

   Why do you call back the cup that is exposed to more air has more h2o on the outside of it?

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

   Some people think that the wet that appears on the outside of a cold cup is water that has leaked through the cup. How does this demonstration prove that this idea is not truthful?

   Because at that place is piddling to no moisture on the exterior of the cup in the bag, students should conclude that water could not have leaked through the cup. If the moisture came from leaking, there would be water on the exterior of both cups.

3. Introduce the process of condensation.

   If students practise non know what the process of condensation is, you lot can tell them it is the opposite of evaporation. In evaporation, a liquid (like h2o) changes state to become a gas (h2o vapor). In condensation, a gas (like water vapor) changes land to become a liquid (h2o).

   Explain that every bit water molecules in the air cool and slow down, their attractions overcome their speed and they bring together together, forming liquid water. This is the process of condensation.

   Ask students:

   What are some examples of condensation?

   Coming up with examples of condensation is a scrap harder than examples of evaporation. One common example is water that forms on the outside of a cold cup or the wet that forms on car windows during a absurd dark. Other examples of condensation are dew, fog, clouds, and the fog yous see when you exhale out on a common cold day.

   You may take fabricated a cold window "cloudy" past breathing on it and then drawn on the window with your finger. Where do y'all call up that cloudiness comes from?

   Help students realize that the moisture on the window, and all of the examples of condensation they gave, comes from water vapor in the air.

   A existent cloud is made upwardly of tiny droplets of water. Where practice you think they come up from?

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

   Give each student an activity canvass.

   Accept students reply questions about the demonstration on the activeness sheet. They will also record their observations and answer questions about the activity. The Explicate It with Atoms & Molecules and Take It Farther sections of the activeness sheet volition either exist completed equally a class, in groups, or individually depending on your instructions. Expect at the teacher version of the activity sail to find the questions and answers.

4. Accept 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

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

   Procedure

   1. Fill a wide clear plastic cup about ⅔ full of hot tap h2o. Identify the tall cup upside down inside the rim of the bottom cup every bit shown.

      
   2. Watch the cups for ane–ii minutes.
   3. Utilise a magnifier to wait at the sides and top of the top cup.
   4. Take the top loving cup off and experience the inside surface.

   Expected results

   The top cup volition get cloudy-looking every bit tiny drops of liquid water collect on the within surface of the cup.

5. Hash out with students what they recollect is happening inside the cups.

   Enquire students:

   What practise you think is on the within of the pinnacle cup?

   Students should agree that the inside of the top cup is coated with tiny drops of liquid h2o.

   How practice you think the drops of water on the inside of the top cup got there?

   Students should realize that some of the water in the cup evaporated, filling the within 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 inside of the summit cup.

   Explain that water vapor leaves the hot water and fills the space above, contacting the inside surface of the top loving cup. Energy is transferred from the water vapor to the loving cup, which cools the water vapor. When the water vapor cools plenty, the attractions between the molecules bring them together. This causes the h2o vapor to change state and become tiny drops of liquid water. The process of changing from a gas to a liquid is chosen condensation.

6. Show an blitheness to help students understand what happens when gases condense to their liquid land.

   Prove the animation Condensation.

   Explain that the fast-moving molecules of water vapor transfer their energy to the side of the cup, which is cooler. This causes the water vapor molecules to slow down. When they tedious downwards plenty, their attractions overcome their speed and they stay together as liquid water on the inside surface of the cup.

7. Hash out how to design an experiment to find out whether increased cooling of the h2o vapor affects the rate of condensation.

   The goal of this discussion is to assist students amend understand the experimental pattern outlined in the procedure.

   Ask students:

   How could we set upward an experiment to come across if making h2o vapor even colder affects the rate of condensation?

   How tin can we get the water vapor we need for this experiment?

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

   Will we need more than than ane sample of water vapor? Should we cool ane sample of water vapor, but not the other?

   Help students empathise that they will demand 2 samples of h2o vapor, only one of which is cooled.

   How will we cool the water vapor?

   Students may have many ideas for cooling water vapor, like placing a sample in a refrigerator or cooler filled with water ice, or placing a sample of water vapor outside if the conditions is cool enough.

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

   By comparing the size of the drops of water formed in both samples, students can determine whether cooling water vapor increases the rate of condensation.

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

   Read more about evaporation and condensation in the teacher groundwork section.

   Question to investigate

   Does making water vapor colder increment the rate of condensation?

   Materials for each group

   • two short wide-rimmed clear plastic cups
   • 2 tall smaller-rimmed clear plastic cups
   • Hot water (well-nigh 50 °C)
   • Magnifier
   • Ice

   Process

   1. Make full 2 broad clear plastic cups most ⅔ full of hot tap water.
   2. Quickly place the taller cups upside down within the rim of each cup of h2o, equally shown.

   3. Place a slice of ice on top of one of the cups.

      
   4. Wait 2–3 minutes.
   5. Remove the ice and utilise a paper towel to dry out the superlative of the cup where the ice may have melted a bit.
   6. Use a magnifier to examine the tops of the two upper cups.

   Expected results

   There will be bigger drops of h2o on the inside of the summit cup below the ice.

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

   Inquire students to make a prediction:

   • What effect do you call up adding the ice cube will take on the rate of condensation?
   • Explain on the molecular level, why yous think actress cooling might touch the rate of condensation.

10. Discuss students' observations and describe conclusions.

    Inquire students:

    Which top cup appears to have more h2o on it?

    The cup with the ice.

    Why do you lot think the cup with the water ice has bigger drops of water on the inside than the cup without water ice?

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

    Does cooling water vapor increase the charge per unit of condensation?

    Yep.

    What evidence do yous accept from the activity to back up your answer?

    Students should realize that the bigger drops of water on the peak cup with the water ice point a greater corporeality of condensation. Because the h2o vapor in both sets of cups was condensing for the aforementioned length of time, the h2o vapor in the loving cup with the bigger drops must accept condensed at a faster rate.

11. Explicate examples of condensation on the molecular level.

    Ask students:

    Fogging upwards a common cold window

    When y'all breathe out, there is h2o vapor in your breath. When you breathe on a cold window in the wintertime, the window gets tiny droplets of moisture on it or "fogs upwardly." What happens to the molecules of water vapor as they go most the cold window?

    The water molecules in your breath are the gas water vapor. They deadening down every bit they transfer some of their free energy to the cold window. The attractions between the slower-moving water vapor molecules bring them together to form tiny droplets of liquid h2o.

    Warm breath in common cold air

    When you exhale out in the winter, yous see "smoke," which is actually a fog of tiny droplets of liquid water. What happens to the molecules of water vapor from your breath when they hit the cold air?

    The h2o vapor in your jiff is warmer than the outside air. The water vapor molecules transfer free energy to the colder air. This makes the water vapor molecules move more slowly. Their attractions overcome their motility and they join together or condense to form liquid water.

    Evaporation and condensation in the h2o cycle

    Ane 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 water wheel?

    Energy from the lord's day causes h2o to evaporate from the land and from bodies of water. As this water vapor moves loftier into the air, the surrounding air cools information technology, causing it to condense and course clouds. The tiny droplets of water in clouds collect on $.25 of dust in the air. When these drops of water go heavy enough, they autumn to the basis as rain (or hail or snow). The rain flows over the state towards bodies of water, where it tin can evaporate again and go along the cycle.

    Projection the epitome Water Bike.

12. Introduce the thought that the amount of h2o vapor in the air affects the rate of condensation.

    Inquire students if they know what a terrarium is. Tell students that a terrarium is a closed container with moss or other plants in which water that continually evaporates and condenses. At get-go, the evaporation rate is higher than the rate of condensation. Merely as the concentration of water molecules increases in the container, the charge per unit of condensation increases. Eventually, the rate of condensation equals the rate of evaporation and the h2o molecules go back and forth between the liquid and the gas.

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

    Projection the animation Evaporation and Condensation

    Explain that the animation moves upwards through a sample of water to the surface. Water molecules evaporate (exit the liquid) and condense (reenter the liquid) at the aforementioned fourth dimension. The blitheness shows the beginning of the process where water molecules evaporate at a faster rate than they condense. Explicate to students that if the process were to proceed, the rate of evaporation and condensation would become equal.

    And so temperature isn't the only gene that affects condensation. The concentration of water molecules in the air is too an important factor. The higher the concentration of water molecules in the air (humidity), the higher the charge per unit of condensation.

    This is why clothes dry out more slowly on a humid mean solar day. The high concentration of water vapor in the air causes water to condense on the clothes. Then even though h2o is evaporating from the clothes, it is also condensing on them and slowing downwards the drying.

13. Have students design an activity to encounter why wind helps things dry more quickly.

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

    Ask students:

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

    As you listen to suggestions from students, be sure that they place and control variables. The paper should be in the aforementioned situation except for air moving over one piece just not the other. It is non a good idea to blow on i considering the breath could be a different temperature than the surrounding air and also contains h2o vapor. These are both variables that would bear on the experiment. It is improve to wave ane of the newspaper towels dorsum and forth for a few minutes and have someone else agree the other or tape information technology then it hangs freely.

    Materials

    • two pieces of brown paper towel
    • H2o
    • Dropper

    Procedure

    1. Place 1 drop of water on 2 pieces of brown paper towel.
    2. Have your partner hold one while paper while you swing the other one through the air.
    3. After about 30 seconds compare the paper towels to see if yous tin can see whatever difference in how wet or dry the papers are.
    4. Repeat stride 3 until yous notice a difference between the wet 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 paper towel on the tabular array had air with a little more humidity over it condensing back onto the paper. This slowed down the drying process. The paper waved in the air didn't have boiling air effectually it and condensing dorsum on information technology as much then it dried more chop-chop.

14. Use the processes of evaporation and condensation to purify h2o.

    Evaporation and condensation tin be used to purify h2o. Imagine what might happen if colored h2o evaporates and so condenses.

    Question to investigate

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

    Materials for each group

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

    Procedure

    1. Add together hot tap water to a broad articulate plastic cup until it is about ⅔ full.
    2. Add ane drop of food coloring and stir until the h2o is completely colored.

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

       
    4. Expect ane–iii minutes for water vapor to condense to liquid water on the inside surface of the height cup.
    5. Use a white paper towel to wipe the inside of the cup to bank check for any color.

    Expected results

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

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

boardmansweld1948.blogspot.com

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

Share this post