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Developed by CLACE- PI Marina La Grave, Dr. Barry Kluger-Bell and Kristine Johnson UNIT: Water LESSON # 1 TITLE: Evaporation Summary: Children learn basic idea about NASA Source: Grade level: Time: Children Learning Outcomes: evaporation and water vapor. Adapted from the NASA sponsored, Aquarius Education and Outreach “Evaporation Investigation” <http://aquarius.nasa.gov/pdfs/evap_inv est.pdf> 3-5 Total time: 70 minutes Snack & introduction: 15 minutes Learning stations: 45 minutes Summary and cleanup: 10 minutes Children will learn that: Liquid water can turn to vapor, a gas, in the air. How fast the water evaporates depends on things like temperature, surface exposed to the air, the amount of water vapor already in the air (humidity) and air movement. Children will engage in and thereby strengthen a number of scientific practices such as: Design and carry out investigations on what effects evaporation rate. Make claims based on evidence about what effects evaporation rate. Communicate ideas about evaporation. Children will be able to (cultural goals): Relate overall science learning goals to the context of their schools, families, and community. Communicate ideas, collaborate with other children, and learn in a personally meaningful way. Big Questions: Where does the water go when the liquid disappears; for example, after it 1 Materials: for evaporation activity Item Water sprayer Electric fan Desk lamp with incandescent bulb String and tape to hang damp paper towels Item Paper towel Ziploc bag Quantity per group of 12–15 1 per adult 1–2 1–2 1 roll each Quantity per pair or trio 4 1 Take-home KIT per child: Each child will receive: 1 small paintbrush 1 half sheet of paper with the following instructions: Wet your paintbrush (under a faucet or by dipping in a container of water). Use your paintbrush to paint different surfaces—a piece of paper, a piece of newspaper, the wall outside, the sidewalk. How do these surfaces look when you paint them with Developed by CLACE- PI Marina La Grave, Dr. Barry Kluger-Bell and Kristine Johnson Lesson format: National Standards Addressed: forms puddles on the pavement or when you put clothes in the dryer? What affects how fast water evaporates? Hands-on activity and discussion. This activity relates to the following standards from the Next Generation Science Standards: K-PS3-1. Make observations to determine the effect of sunlight on Earth’s surface. K-ESS2-1. Use and share observations of local weather conditions to describe patterns over time. 2-PS1-1. Plan and conduct an investigation to describe and classify different kinds of materials by their observable properties. 2-ESS2-3. Obtain information to identify where water is found on Earth and that it can be solid or liquid. 4-PS3-2. Make observations to provide evidence that energy can be transferred from place to place by sound, light, heat, and electric currents. 5-PS1-1. Develop a model to describe that matter is made of particles too small to be seen. 5-ESS2-1. Develop a model using an example to describe ways the geosphere, biosphere, hydrosphere, and/or atmosphere interact. 5-ESS2-2. Describe and graph the amounts and percentages of water and fresh water in various reservoirs to provide evidence about the distribution of water on Earth. water? Watch your “paint” marks as they disappear. What happened? Can you relate it to what we did today? Please remember to bring in a show and tell object that makes you think about water or a drawing related to water for next week. Word Wall: Include following words in discussion (in both English and Spanish), orally defined in understandable terms, and visibly displayed. If possible, project a large image of the words (and associated pictures) on the wall of the teaching area. Evaporation • Evaporación Water vapor • Vapor de agua Liquid water • Agua líquida Transpiration • Transpiración DIRECTIONS: Overview: This session involves three parts and one take-home activity: 1) Start with a discussion about where they think water goes when things dry out. 2) Children then investigate things that might affect the rate of evaporation. 2 Developed by CLACE- PI Marina La Grave, Dr. Barry Kluger-Bell and Kristine Johnson 3) Children share their results and the facilitator discusses evaporation and transpiration. 4) Instruction for Take-home Kit/activity. Steps: LESSON INTRODUCTION (15 minutes) At the beginning of the session (during snack, if provided), show a multimedia presentation to introduce today’s lesson. o http://www.youtube.com/watch?v=k9l0s5zVibo Relate today’s topic to the last unit (air). Water is another component of the earth system, and this unit will be all about water. Remind the children that by learning about water, they will gain a better overall understanding of climate change, because water is one of the important elements of our environment. Start with a question? Ask the children, “Where do you think the water goes when puddles on the playground disappear?” Take all answers as you are trying to get access to the thinking that children start with o Ask the children to explain why they think that—what evidence do they have to support their theories? Tell students that they today are going to be looking at something where two components of the Earth’s system; air and water, combine. They will think about clouds. Discussion question: o Ask students what they think clouds are? Be open to all ideas that they generate. o Then tell them that today, they will hear what scientists have learned about clouds and will be able to make their own cloud in a bottle. o Show the first 2 minutes of the video http://www.youtube.com/watch?v=HNjESP1CKSg&feature=related Follow with more questions: o Where does the water go from the wet clothes you put in the dryer? o Ask children to predict what will happen to the water if it is left out for a day in an uncovered dish? Ask children what will happen if the dishes were covered? o Ask what they think might make the water disappear faster or slower? o Ask the children to explain why they think that—what evidence do they have to support their theories? If they have difficulty thinking of what might make water disappear faster or slower, remind them of the dryer—does it have different settings? Why? What do they do? Would water disappear faster from a tall narrow drinking glass or a saucer? Why—what reasoning do they have to support their theories? Introduce the word evaporation. Tell the children that this process of water “disappearing” into the air is called evaporation. Then tell them that today, they will 3 Developed by CLACE- PI Marina La Grave, Dr. Barry Kluger-Bell and Kristine Johnson experiment to find out what makes water evaporate slower or faster. LESSON LEARNING TASKS (40 minutes) Procedures Divide the children into groups of 2 or 3. [Have each group of children get two or more paper towels.] Discuss what they think will make paper towels dry faster, or slower. Show them that you have: a place to hang towels, plastic bags to put towels in, a sunny spot or hot light bulb, and a fan. They should also try crumpling/wadding/folding the damp paper up vs. laying it out flat. Have each group pick one thing to change so that they can test how that one thing effects how fast water evaporates. For example, they can choose to place one wet towel in the sun, hang it, wad it up, put it in a plastic bag or put it in front of the fan. Try to have at least one group examining air movement (the fan), surface area (wadding), heat (sun/light bulb), and humidity (the bag). Place the second towel on the table in front of them. The facilitator will lightly mist all of the paper towels with about the same amount of water using the sprayer. (Count the number of sprays and be consistent between towels.) Have each group of children observe and record what happens to the water. Which towel dries fastest? While waiting for their towels to dry, they can look at what other groups are trying and/or record predictions and observations in their journals. If there is time and the group is organized enough, they can test another variable. Discuss what is going on here. See the background information above and below, and move into the discussion and summary. Which towel(s) dried faster? Which dried the slowest? Can you rank them from fastest drying to slowest drying? Based on your observations, what conditions do you think increase or decrease the rate of drying—the rate of evaporation? Why? Give evidence for your ideas. LESSON DISCUSSION AND SUMMARY (15 minutes) After the activity, work with the children to summarize their results. Asking the questions 4 Developed by CLACE- PI Marina La Grave, Dr. Barry Kluger-Bell and Kristine Johnson below, have children talk with their partner about their answers. Then have them share their answers with the whole group. Have the group discuss the results after the pair discussion. What things made the water evaporate faster? What things made the water evaporate more slowly? Explain to the children that the process of water evaporation is actually water "going" into the air. The liquid water turns into water vapor (an invisible gas like air). Ask children for some other examples of evaporation (for example, clothes drying when they are wet or the water in a pail or glass disappearing when it is left out for a period of time. Discuss what is happening with the water—which treatments “speed up” the water and help it leave the surface of the towel? Which slow it down? Discuss where evaporation takes place in the water cycle. When there is water on the ground or in lakes or streams or in the ocean, some of it evaporates. Water from parts of plants can also turn into water vapor in the air directly in a process called transpiration. The water vapor in the air can eventually make clouds. From this lesson, children should have learned: Liquid water can evaporate and become water vapor in the air. A variety of things can affect the rate of evaporation. TAKE HOME Children will take home a half sheet of paper with suggested discussion questions to ask family and friends (in both English and Spanish). Introduce the Take-home activity with a short discussion on “Where do you see evaporation happening in or around your home? Where does water disappear or where do wet things dry out?” Children will receive a small paintbrush and a half sheet of paper with the following instructions: Wet your paintbrush (under a faucet or by dipping in a container of water). Use your paintbrush to paint different surfaces—a piece of paper, a piece of newspaper, the wall outside, the sidewalk. How do these surfaces look when you paint them with water? Watch your “paint” marks as they disappear. What happened? Can you relate it to what we did today? Please remember to bring in a show and tell object that makes you think about water or a drawing related to water for next week. ASSESSMENT: Ongoing, through the discussion and activities: monitor children’s usage and understanding of words and ideas related to today’s lesson. Ask supporting questions to encourage children to make connections. Clarify misconceptions. 5 Developed by CLACE- PI Marina La Grave, Dr. Barry Kluger-Bell and Kristine Johnson Demonstrations of understanding: do any drawings, writing, theater, etc., display sophisticated, accurate understanding of today’s lesson? Were children able to make personal connections to the ideas? Were children able to make connections to prior lessons? Take- home work (assessed following week): did children follow through and discuss the lesson with their families, bring a related show and tell object, and/or make a drawing/other art project related to today’s lesson? Did discussion around these things show continuing understanding of the ideas, including making connections to prior lessons and to community? Do children’s understandings, as displayed by their demonstrations of understanding, questions, and discussion show connections between today’s topic, and the big picture of the unit topic? RELATED NASA ACTIVITIES AND RESOURCES: NASA SCIENCE - Earth: Water Cycle http://science.nasa.gov/earth-science/oceanography/ocean-earth-system/ocean-watercycle/ This site discusses the water cycle with particular emphasis on the oceans role in the water cycle and NASA study of that process. Earth Observatory: A Multi-Phased Journey http://earthobservatory.nasa.gov/Features/Water/page2.php This Earth Observatory site discusses the water cycle (hydrologic cycle) providing good background information for facilitators. Earth Observatory: Will runaway water warm the world? It’s not the Heat, it’s the Humidity http://earthobservatory.nasa.gov/Features/WaterVapor/water_vapor3.php This site explains the concept of relative humidity. Global climate change - interactives: The Water Cycle http://climate.nasa.gov/h2oWaterCycle/index.cfm This site presents a very nice interactive graphic describing the water cycle. BACKGROUND INFORMATION: Evaporation is the process of liquid water leaving through the surface of the liquid and becoming a gas in the air. This gaseous phase of water is called water vapor. On the Earth, water is constantly evaporating and entering the atmosphere. Evaporation is critical to driving weather and climate. It is a primary means for transferring heat within the weather cycle. The sun powers the weather cycle. Fully 25% of the sun’s energy received at the Earth’s surface goes into evaporation. Water entering the air as vapor provides the energy that drives the water cycle. The water vapor in the air is also a major natural greenhouse gas that helps keep our planet warm. Water is transported from place to place primarily by wind, moving air, causing vapor and clouds in the atmosphere 6 Developed by CLACE- PI Marina La Grave, Dr. Barry Kluger-Bell and Kristine Johnson to move. A huge amount of water is moved every day. An average of 3 mm (1/8 inch) of water is evaporated over the entire surface of the Earth every day. This amount is higher in the tropics and over the oceans, lower in the arctic and antarctic regions and almost zero over deserts. To understand evaporation, you have to think about water at the molecular level. In liquid water, molecular forces hold the molecules together but they are all moving around at a range of speeds. In cold water, the average speed is lower and in warm water, the average speed is higher. Some of the molecules are moving fast enough to break through the surface, escaping the forces that hold the liquid together, and moving into the air. These escaping molecules carry away energy from the liquid. Since the fastest molecules are the ones that escape, the average speed of molecules in the liquid decreases. The temperature of the liquid then decreased, since temperature depends on the average speed of the molecules. The rate at which water evaporates depends on a number of factors. As mentioned above, higher temperatures mean that liquid water molecules are moving at a higher average speed. This means more molecules are moving fast enough to escape so the rate of evaporation increases with water temperature. But molecules need a surface between the air and liquid water to escape through. If that surface is small, few molecules will escape. But as the water is spread out and the surface in contact with the air increases, there is more surface to escape from and the rate of evaporation increases. Another factor that influences evaporation rate is the amount of water vapor already in the air or relative humidity. In addition to water molecules passing from liquid to air across the surface, there are also water molecules from the vapor in the air passing back into the liquid. The higher the humidity, the more water molecules are in the air so there are more passing back into the liquid. High humidity will lower the overall rate of evaporation. Finally, if the air near the surface of the water is not moving, escaped water molecules will build up in the air near the surface, increasing the humidity near the surface and lowering the rate of evaporation. However wind or other air motion can bring fresh, drier air near the surface and increase the rate of evaporation. As mentioned above, moving water from liquid into the air as vapor requires energy and removes the fastest molecules from the liquid. This lowers the average energy per molecule and hence, lowers the temperature. This process is called evaporative cooling and is why sweat, evaporating from our skin, can cool us off. On the Earth’s surface, energy for rewarming the cooled water comes from the Earth’s surface, which is heated by the sun. Evaporative cooling and convection (hot air rising and cool air filling its place) keeps the Earth’s surface from overheating. The water vapor in the air is carried upward by convection, condenses to form clouds, and precipitates down as rain, snow or hail. Energy absorbed from sunlight is carried away from the surface in water vapor and released to the atmosphere when vapor condenses into clouds. This transport of heat energy powers the weather systems on the Earth. CULTURAL BACKGROUND INFORMATION: 7 Developed by CLACE- PI Marina La Grave, Dr. Barry Kluger-Bell and Kristine Johnson Water is one of the natural resources present in all aspects of human civilization. Historically, the need and demand for water has been one of the driving forces for social organization, economic prosperity, culture, development and health. Then and now, the efficient use of this resource largely determines how one perceives, assesses and manages it. Its effective use represents individual and collective well-being of communities. Historically, communities of the world honored and worshiped this important natural resource. In its unique way, they created stories, gods, symbolisms and characters that highlighted its importance: To most Native American tribes, water was used as a clan symbol. To the Hopi, Navajo, and Pueblo tribes the water clan named is Piikyasngyam. To Peruvians, the god of water was Naylamp. It was believed that Naylamp came from the sea, and brought civilization to the lands of Lambayeque. To Hindus, Ganga was the goddess of the Ganges river and is represented ridding a sea monster. In Norse mythology, Ægir is the king of the sea, and is a personificates of the power of the ocean. To Greeks, Neptune governed all waters and seas. To Mayas, Tlaloc (sometimes called Nuhualpilli) was the Nahuatl name of the God of water and fertility in Teotihuacan and Nahuatl religions. For the Egyptians, Sobek - was the water God. They believed that the Nile water came from the sweat of Sobek and he was the god of all surface water. To Japanese, Kappa is a mythological creature that lives in lakes, rivers and wetlands. The list goes on! Make sure to encourage your students to do a little research on a culture of their choosing. LESSON CONNECTIONS This lesson is tied to ideas in other lessons: In Lesson 2 (Condensation and the Water Cycle), children learn some basic ideas about condensation and how water vapor changes to liquid water. This is followed by using this understanding of condensation and what children learned about evaporation in the last session to introduce the water cycle. In Lesson 3 (Clouds), children gain some basic ideas about what clouds are and how they form, drawing from what they learned in the previous two lessons (on evaporation and 8 Developed by CLACE- PI Marina La Grave, Dr. Barry Kluger-Bell and Kristine Johnson condensation). The lesson starts with everyone watching the first 2 minutes of a NASA video on clouds. Then each group does an experiment, assisted by the facilitator, where they make a cloud in a bottle. In Lesson 4 (Water and Life) children answer the question, “Why do living things need water?” It has two active parts and a discussion. Children start with looking at how plants take up water by doing the classical celery in colored water activity. This will require saving materials to view in the next session. Next, children do a simple activity to get across the idea that many chemical reactions (particularly biochemistry) need water to happen. In Lesson 5 (Precipitation, Collection, and the Water Cycle), children delve deeper into the water cycle in a three-part experience. The first part is a demonstration/observation activity that models precipitation. The second is a discussion of what happens to the water after it hits the ground. In the third part, children build closed system terrariums that show the whole water cycle in miniature. 9