Grade Level: Elementary
Time Activity 1: One 20 min. period, with follow up 10 min observation sessions, 30 min. wrap up;
Time Activity 2: Two 30 minute periods
Content Standard: NSES Physical Science, properties of objects and materials
Ocean Literacy Principle 1f: The ocean is an integral part of the water cycle and is connected to all of the earth's water reservoirs via evaporation and precipitation. |
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Big Idea |
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Water can "disappear" or evaporate into the air. |
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Key Concepts |
- Evaporation occurs when a liquid is changed into a gas.
- Rate of evaporation increases when the temperature of a liquid is increased.
- Water moves around our planet in the water cycle.
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Essential Questions |
- How does water change?
- How does water move?
- How does life depend on water?
- Where does water go when it is evaporated?
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Knowledge and Skills |
- Observe the process of evaporation or the "disappearance of wetness into the air."
- Compare and contrast their observations made before and after the evaporation experiement.
- Construct a diagram of the experiment and use it explain the results.
- Describe the process of evaporation, and the general water cycle, through discussion and pictures.
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Prior Knowledge |
- Some events in nature have a repeating pattern - such as daily weather patterns or changes in temperature and the appearance of rain and snow at different times of the year.
- Water can be a liquid, solid or gas and can go back and forth from one form to the other.
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Common Preconceptions |
- At the elementary grades, evaporation and condensation will mean nothing different from disappearance and appearance.
- Students have a difficult time accepting the idea of invisible particles of water in the air.
- Students understand the concept of boiling and freezing well before understanding evaporation and condensation.
- When water evaporates, it just disappears and ceases to exist.
- When water evaporates, it immediately goes up to the clouds or into the sun.
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Concept Map |
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Primarily for the teacher's use, the map provided here relates to the branch "Phases of Water" from the comprehensive Aquarius Concept Map - Water & its patterns on Earth's surface.
From the comprehensive Aquarius Concept Map: Water and its patterns on Earth's Surface. |
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Background |
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Evaporation is the process by which water changes from a liquid to a gas or vapor. Evaporation is the primary pathway that water moves from the liquid state back
into the water cycle as atmospheric water vapor. Studies have shown that the oceans, seas, lakes, and rivers provide nearly 90 percent of the moisture in the
atmosphere via evaporation, with the remaining 10 percent being contributed by plant transpiration.
Evaporation from the oceans is the primary mechanism supporting the surface-to-atmosphere portion of the water cycle. After all, the large surface area of
the oceans (over 70% of the Earth's surface is covered by the oceans) provides the opportunity for large-scale evaporation to occur. On a global scale, the amount
of water evaporating is about the same as the amount of water delivered to the Earth as precipitation. This does vary geographically, though. Evaporation is more
prevalent over the oceans than precipitation, while over the land, precipitation routinely exceeds evaporation. Most of the water that evaporates from the oceans
falls back into the oceans as precipitation. Only about 10% of the water evaporated from the oceans is transported over land and falls as precipitation. Once
evaporated, a water molecule spends about 10 days in the air. The process of evaporation is so great that without precipitation, run-off, and groundwater
discharge from aquifers, oceans would become nearly empty.
Less evaporation takes place during periods of calm winds than during windy times. When the air is calm, evaporated water tends to stay close to the water body.
When the winds are present, the more moist air close to the water body is moved away and replaced with drier air which favors additional evaporation. |
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Materials |
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Activity 1 - containers with lids (coffee can works well), water, wooden stirring sticks (paint stirrers work well), markers, colored sticky dots, measuring cups; optional materials include, construction paper, glue.
Activity 2 - salt, warm water (aids dissolving of the salt), paper, paint brushes, food coloring, measuring cups, containers (plastic cups work well and can be reused), spoons for mixing.
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Preparation |
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Break students into working pairs for both activities. For Activity 2, pre-measure a 1/4 cup of salt into one set of containers for each student pair. Depending on how many colors you want each group to have you'll have to calculate how many containers and how much salt you'll need. |
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Activity 1 |
- Show students a coffee can half filled with water. Provide the following instructions to the students:
"Each group will receive two coffee cans that will each be filled with the same amount of water. You will cover one of the cans and leave the other one open. Over the next few days you'll watch the cans to find out what happens to the water. Your job is to keep a journal that shows the results of what you see happening in each can. We will talk about what happens at the end of our study."
- Each student pair should label their cans with their names. Mark each can with a colored dot.
- Show the students the wooden stirrers. Ask the students how they could be used to test what happens to the water level over time.
- Each group/pair should use their measuring cup to fill each can with the same amount of water.
- Have students measure the water levels by dipping their wooden stirrers into the water at the side of the can until it touches the bottom. They should make a thin line on their wooden stirrer at the water line (could be made first with a pencil and then re-marked for visibility with a marker). Mark the stirrers with another colored dot that matches the coffee can colored dot where the measurement was taken.
- Place the can in a safe area and instruct the students to cover one of the cans. Explain again that one of the cans will remain covered for the tests. They can uncover it to take their measurements but then must re-cover it when they are finished.
- Students should check the cans on a regular basis (daily or every other day) and record observations in their journal. Based on their observations, the students should draw an illustration in their journal that shows what is happening to the water in the cans over time.
- Extension - have each group glue its marked stir sticks to a piece of construction paper. After the sticks have been glued, students should label each of the lines for the days of measurements that were taken. The students should use this graphic to help them answer and understand the questions in the Assessment section.
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Activity 2 |
- The students will paint with saltwater paints and witness evaporation taking special notice that only the water evaporates and the colored salt is left behind.
- In advance of the painting, discuss weather and the water cycle. Use a diagram of the water cycle to facilitate the discussion. Explain how energy (from the sun) warms the water in bodies of water like the oceans and lakes and the water evaporates into the air. The water vapor in the air condenses into clouds. The clouds become filled with water and falls as rain back into the oceans and on the land.
- Provide the saltwater painting materials to each group. Instruct them to pour the salt into the warm water and gently stir until the salt has dissolved. The teacher will come around to each group with the food coloring and help the students add it to their saltwater mixtures. This also allows the students to choose the colors.
- Ask the students to paint scenes that are related to the water cycle using the colored, saltwater mixtures.
- Lay the paintings to dry overnight.
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Activity 1 adapted from "Disappearing Water" - Science NetLinks. Activity 2 adapted from The Educator's Reference Desk (J. Van Loy) |
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Assessment Activity 1 |
- Using a white or chalk board to record the student's answers, ask the following questions:
- What happened to the level of the water in the closed container?
- What happened to the level of the water in the open container?
- Is there a difference in what we saw happen between the two containers? What is the difference?
- What did we do that was different with the containers?
- What if we used a different kind of container (e.g., jars instead of cans)? Do you think the result would be different? Why or why not?
- Have students draw the results of what they observed for each of the containers. They should be prepared to share and describe their drawings.
- Have students share their pictures and describe the results that they saw for each of the studies. In both cases of the open container, what happened to the water in it? What happened to the water in the closed container? If you had a glass of water that you wanted to save, should you leave it open or closed? Why?
- Ask students to write and then share a brief response to the following scenario. "
It rained last night. You notice a puddle in your yard the next morning and splash around in it for a little while. Your mom tells you to come inside to get ready to go to the beach because it is a warm, sunny day. When you return in the afternoon to play in the puddle it has changed. What do you think will have happened to it? What if it wasn't a warm, sunny day and instead a gray, cloudy day, how will that affect the puddle? Draw a picture that illustrates what has happened. "
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Assessment Activity 2 |
- The following day, students will examine their paintings to find that the water has evaporated but the colored salt remains.
- After a group discussion about evaporation, have the students write a brief summary of what happened to their painting. Ask each student to explain how the process of evaporation relates to the scene depicted in his or her painting.
- OPTIONAL: If the range of scenes illustrated by the group includes rain, snow, clouds, a lake or ocean, then conduct a gallery walk of the students' artwork. As a group, categorize the paintings by which part(s) of the water cycle they depict (i.e. precipitation, evaporation, both).
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Wrap Up |
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Re-engage the essential questions in a class discussion for review. |
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