Now You See It, Now You Don't
Grades 3-5

This lesson investigates the process of evaporation. Through video and hands-on activities, students will better understand how and why molecular movement is responsible for the evaporation of liquid. This is a two-part lesson, with data collection taking place over at least a two-week period in Part One.

EUREKA! #18 "Evaporation and Condensation"
To get a copy of the video, please contact:

TV Ontario
(919) 380-0747

IT FIGURES #16 "Bar Graphs"
To get a copy of the video, please contact:

Agency for Instructional Technology
(800) 457-4509

Students will be able to:

• Name the three states of matter
• Explain the difference in the movement of molecules found in the three states of matter
• Demonstrate recognition of the fact that molecules are too small to see unless millions are together
• Discuss and report on the process of liquid evaporation
• Record data on water evaporation occurring in different containers
• Identify the parts of a complete graph
• Interpret data from the experiment and apply it to a graph
• Formulate a conclusion based on data from a graph.

For each student:

• Eye dropper
• Small container of water (film canisters work well)
• Paper towel

For each group of 4 or 5 students:

• Data Collection Sheet for graphing *

For the class:

• 1 long jump rope or several shorter ones tied together
• 4 or 5 clear containers of different sizes and/or different shapes
• Paper centimeter-rulers
• Food coloring

* Located at the end of the lesson.

Vocabulary:

• Evaporate - to convert into vapor
• Gas - a fluid (as air) that has neither independent shape nor volume but tends to expand indefinitely
• Liquid - flowing freely like water
• Molecule - the smallest particle of a substance that retains all the properties of the substance and is composed of one or more atoms
• Property - a quality or trait belonging, and especially peculiar, to an individual or thing
• Solid - a substance that does not flow perceptibly under moderate stress
• State - a mode or condition of being.

Part 1-A:

If the students have some prior knowledge of the three states of matter, you may be able to omit the following part of the lesson.

TEACHER: "Today we are going to learn about liquid and some of its properties. First let's find out a little about the three different types of matter." Place 1 or more jump ropes on the floor to form a circle about 5 or 6 feet in diameter. Ask for 8 volunteers and explain to them that they will represent water molecules in the three different states of matter.

Solid:
Instruct your volunteers they are to move back and forth inside of the rope circle but that they cannot move their feet.

TEACHER: "Our circle represents a drop of water. The people inside of the circle are molecules. What happens when you put water in the freezer?" (It turns to ice.) "Think about an ice cube, describe its shape." (A definite cube.) "Can you pour an ice cube like water?" (No.) "Can you put your finger into it?" (No.) "Why not?" (Because it is solid.) "Solid matter keeps its shape because the molecules are stuck in place even though they are always moving. What happens to an ice cube when you leave it in the sun?" (It melts.) "Why do you think this happens?" (The molecules are no longer stuck in one place.)

Liquid:
TEACHER: "Let's pretend you are our ice cubes in the sun and see what heat does to the molecules." Instruct your volunteers to move about inside the circle. They need to move more quickly and move their feet around but must stay inside of the circle. "What do you notice about our ice cube now?" (The molecules are moving around faster.) "What is happening to its solid form?" (It's losing form, melting.) "Right, our ice cube is now a puddle of water. How is water different than ice?" (You can pour it, put your finger in it.) "What made the molecules move faster?" (Sun, heat.)

Gas:
TEACHER: "If you spilled some water on the sidewalk in July, what would happen to it?" (It would dry up.) "What would it look like 2 hours after you spilled it?" (It would be gone.) Instruct your volunteers to move about quickly and when they bump into another molecule to leave the rope circle and move about the classroom. You may want to give them a start signal this time. "Now our puddle of water has been out in the sun for a while. Let's see what happens to the molecules when they get even hotter." Teacher signals to the volunteers. Within a few seconds, all of your molecules should have left the circle and be moving around the classroom. "Now that the molecules have left the puddle, where are they?" (In the room, moving around.) "How many molecules are left in the puddle?" (None.) "That's right, they are now moving around in the air and are called a gas." Ask your volunteers to return to their seats.

TEACHER: "Turn to your neighbor; one of you tell the other how the molecules move in a solid. Now, the other partner, tell how molecules move in a liquid. First partner again, tell how molecules move in a gas. Second partner, tell what the three types or states of matter are." Allow time after each direction for the students to complete the task. OBJECTIVES 1 & 2.

Part 1-B:

Prepare a small container of water and an eyedropper for each child. Ask the students to put one small drop of water on the back of their hand with the eyedropper. Instruct them to observe the drop while they blow on it gently. Allow a few minutes for them to do this. Ask the students to turn to their neighbor and explain what happened. Ask several students to share what they think happened, while the teacher places their responses on the chalkboard or on a large piece of paper.

It is important to give students a specific responsibility while viewing. Knowing what they are expected to learn allows them to focus on specific information and concepts in the video.

TEACHER: "Listen for the reason liquids do not have a definite shape. When you hear it, raise your hand."

RESUME video.
PAUSE after the character flies out of the fish bowl. Check for understanding. Students are to explain to their group or the whole class the similarities and differences between the popcorn and the molecules in the video.

TEACHER: "Watch this next segment to discover whether or not you can see molecules and why."

RESUME video.
PAUSE after the narrator says, "when they make up the water in your goldfish bowl," and there is a picture of a fish. Check for understanding. Ask students to share with a neighbor when they can see molecules. OBJECTIVE 3.

TEACHER: "Listen and be able to tell me what water is called when it is in the air and what we call it when it changes from liquid to gas."

RESUME video.

STOP after the narrator says, "evaporation." Check for understanding. Students in their group discuss the nature of evaporation. Give the groups time to reach an agreement on the definition. The groups report to the whole class, and all record their definitions. Compare definitions to summarize learning or main points. Develop a class definition. OBJECTIVE 4.

The teacher brings out 4 or 5 clear containers of different shapes and/or different sizes. Make sure that they have different surface areas for the water. Label the containers A, B, C, D, etc.

TEACHER: "Let's experiment with evaporation. If we put water into these containers and leave them in the classroom in a quiet place, what do you think will happen to the water? With your group, make a prediction about the containers according to the following: fastest evaporation, next, next, and the slowest. Write your predictions on your paper." Allow time for the students to discuss the predictions and reach a group agreement. Post each groups' predictions on butcher paper for later reference.

TEACHER: "A paper ruler will be taped to the side of each container, and it will be filled with water." Color the water for easier reading.

TEACHER: "How will we keep track of how much water evaporates?" Teacher or students will list suggestions and choose one that will work.

Note: A Sample Data Collection sheet is included at the end of this lesson. The teacher could have groups collect their own data or assign a group or a student to record the changes in each container for the whole class.

Students should collect data at least 3 times a week. After they have collected data for at least 2 weeks, move on to PART 2 of the lesson. OBJECTIVE 5.

Part 2:

Video: IT FIGURES #16 "Bar Graphs"

TEACHER: "We are going to watch part of a video that will resemble a favorite fairy tale. Listen to discover the queen's problem."

CUE video to the beginning of the "Queen of Hearts" cartoon and START.
PAUSE after the narrator says, "she's been running out of tarts long before the end of the week!" Check for understanding. Ask the students to name the queen's problem. Discuss responses and make sure they understand the problem.

TEACHER: "Predict how you think the queen will solve this problem. Tell your prediction to your neighbor."

Note: Allow a minute for them to think and share. "Now let's listen to what the queen chooses to do."

RESUME video.
PAUSE after the queen says, "might give us a clue," and the king nods his head.

TEACHER: "Raise your hand if your prediction about the queen was correct. From the next segment, be able to tell your neighbor what kind of information is collected and what it looks like."

RESUME video.
PAUSE after the queen says, "Isn't there a simpler way to show how many tarts were eaten each day?" and the king runs off.

TEACHER: "What did the information look like? Was it easy to understand? Can you think of a better way to show this information?" List some of their suggestions on the chalkboard, or have them tell their neighbor. "Now listen to what the king thinks is a better idea. Be ready to tell your group."

RESUME video.

STOP after the queen says, "write down the same things for week 2 and week 3," and the king runs off. Teacher directs students to list on paper, or orally, the parts of the graph that were missing. OBJECTIVE 6.

TEACHER: "Let's decide how we can use the information about graphs to help us record our own data from our evaporation experiment." Students design graphs in their group based on the data collected from the experiment. OBJECTIVE 7.

When they are finished, bring them together in a large group and have each group present their graphs. When all graphs have been presented, try to reach a conclusion about which container had the most and least evaporation and why. This conclusion should be checked against the students' earlier predictions. OBJECTIVE 8.

Assessment: Check for student understanding of the graph results and the concept of evaporation. Activities under Action Plan and Extensions are suitable for assessment, also.

Invite a speaker from a water management company to reinforce and expand on "molecules" and "evaporation."

Let students design experiments with evaporation from containers covered with different materials such as cotton, nylon, or plastic and discuss how these things might be useful and why. This activity may be used as assessment.

Art:
Students draw pictures on black or blue paper and "paint" over it with a solution of 1/3 cup Epson salts dissolved in 1/2 cup water. When the water evaporates, crystals will be left.

Science:
Does water evaporate from plants? Design "a discovery," or use the following:

1. Wet 2 paper towels equally, straighten one out, and leave one in a crumpled ball. Check often to see which dries out first. Discuss the results.

2. Wet 2 paper towels equally, wrap one in wax paper, and leave one without. Which dries faster? Relate this to the waxy skin of cacti and other desert plants. Is water the only liquid that evaporates? Students hypothesize about this matter and then design an experiment to determine this, and graph results of the findings. They will need to validate their hypotheses and summarize their findings.

3. Both of these activities in science may be used for assessment.

4. Other ITV courses from ASSET on the topic of evaporation:

• MAGIC SCHOOL BUS, Series 2, #6 "Wet All Over"
• SCIENCE IS ELEMENTARY #3 "Let's Explore Water"
• 3-2-1 CLASSROOM CONTACT #12 "Go with the Flow"
• VOYAGE OF THE MIMI #19 and #20 "Making Dew" and "Water, Water Everywhere."

Click here to view the worksheet associated with this lesson.

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Master Teacher: Ann Parra