Lesson 8 of 14
Objective: SWBAT model the steps of the water cycle and describe what is happening at each step.
The Why Behind Teaching This
Unit 5 covers standards relating to Earth's Systems. It covers Standard 5-ESS2-1: Develop a model using an example to describe ways the geosphere, biosphere, hydrosphere, and/or atmosphere interact. Students will be learning the difference between each of the systems, and ways that each of the systems interact to help make Earth what it is today. The other standard covered is Standard 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.
Modeling will be an important component of this unit. Students will be modeling layers of Earth, the water cycle, land forms, and more. The unit begins with an overview of all the systems, then each system is taught in isolation. As each new system is covered, how it depends on or interacts with the previous systems will be addressed. In addition to the end of unit assessment, there will also be a culminating activity where groups build a model to demonstrate how 2 of the systems interact. Connections to several previously covered standards will also be made throughout this unit.
This specific lesson is related to both standard 5-ESS2-1 and 5-ESS2-2. The water cycle is part of the hydrosphere, understanding the steps of the water cycle will help students see how it is related to the other systems. It is related to standard 5-ESS2-2 because students must understand that the majority of the water that evaporates comes from oceans because the majority of the water on Earth is found in oceans.
Students will be able to identify the major steps of the water cycle and explain what is happening at each step.
Students will demonstrate success on this lesson goal by correctly listing 5 key transitions in the water cycle during the modeling activity.
Preparing For The Lesson:
- Chart paper for the water usage list
- notebooks for diagramming
- a copy of the Water Cycle Diagram Labels for ESE and ELL students who need the modification.
- a large bowl for each group
- clay for each group
- hot water for each group (enough to cover the bottom of the bowl)
- wax paper
- ice cube for each group
- notebooks for illustrating and labeling the diagram
- Paper for writing the water cycle story
Water On Earth
I have a sheet of chart paper hanging on the front board titled "Uses for Water". I ask students to name ways that we use water. I list the uses as students name them. They include things such as drinking, showering, washing clothes, washing dishes, washing our pets, filling swimming pools, and watering the lawn.
After creating the list, I tell students that the water we use for all of those things is the same water that the dinosaurs were swimming in hundreds of millions of years ago. How is that possible? Students discuss this question with their table group and then share their thoughts. One group says that water evaporates and then it rains and it continues to do this over and over. Another group says that water goes from the atmosphere to lakes, rivers, and oceans, and then back to the atmosphere, and then it falls into lakes, rivers, and oceans again. By hearing some of their ideas I am able to get an idea that most students have some background knowledge in this area and are familiar with at least some of the vocabulary which we did cover earlier in the year when we talked about matter changing states.
Diagramming the Water Cycle
The same water has been on Earth for hundreds of millions of years because it is continuously going through a cycle called the water cycle. This cycle can begin at any point but we are going to begin with it here on Earth as collection. Students take out their science notebooks so we can begin diagramming the water cycle. I place my notebook on the overhead for students to copy from. This is a good strategy for students who need a visual representation of what is being discussed. As students take out their notebooks, I pass out a copy of the Water Cycle Diagram Labels to the ESE/ELL students who need the modification of having copies of written information. They will glue in the information as I write and the other students copy.
I begin by asking the students to think about our lesson yesterday on the water here on Earth. What are some examples of places where water collects on Earth? They respond with lakes, rivers, ponds, oceans, streams, ice caps,and reservoirs. Where is the majority of the water on Earth located (this is a review from our previous lesson)? They tell me oceans.
To begin our diagram I draw a mountain that leads down into the ocean and label the ocean as collection.
The water does not just sit in the oceans, lakes, and streams forever. What happens to the water that has collected here on Earth? Students tell me that it evaporates. What does that mean? What is happening to the water when it evaporates? Their response is that it is changing into a gas. I continue asking questions to get them to explain with more detail. This is a great time to review changes of state from the beginning of the year. Students need to know what is happening to the particles of water as it travels through the water cycle, not just the names of the steps. What causes it to change into a gas? Heat from the sun. How does the heat change the particles of water that make it change from a gas to a liquid? It causes the particles to move faster and spread apart.
I draw arrows pointing up and write: Evaporation - heat speeds up the particles changing them from a liquid to a gas.
I ask students to explain what is happening to the particles of water vapor as they rise up through the atmosphere. This is a difficult question for students to answer so I give them something they are knowledgeable of to relate it to. I point to the mountain in the picture. What happens as you get higher up the mountain? They tell me that it gets colder. I explain that the same thing happens to the particles of water vapor that are moving up through the atmosphere, they begin to cool off. What happens to the particles of a gas when they get colder? They get closer together and slow down, changing back into a liquid. Does anyone know what this step of the water cycle is called? Condensation. I explain that as the water vapor cools and changes back into a liquid, the drops collect together, which forms a cloud.
I draw clouds in the diagram and label them: Condensation - Water vapor cools and changes back into a liquid.
Eventually the cloud will fill up with tiny water droplets. What will happen once the cloud fills up? Students tell me that it will rain. What if it is really cold out, will it still rain, or will something else fall? Students tell me that if it is cold enough it would snow instead of rain. This step of the water cycle is called precipitation and there are actually four types of precipitation. What else could fall from the clouds besides rain and snow? Although most of the students have never seen hail or sleet, they do know the two terms.
I draw water droplets over the water and snow flakes over the mountain and label it, Precipitation. As I write each type of precipitation under the heading, I describe what it is and when it would fall. Rain - liquid...hail - ball of ice before big storms...sleet - small pebbles of ice, starts as rain & freezes on the way down...snow - ice crystals form in the clouds.
The rain that falls into the lakes, rivers, and oceans will collect again and the process will start all over. What about the water that falls on the land? Or the snow that falls on top of the mountain? Students tell me that the snow melts and runs down the side of the mountain back into the ocean. Water that falls on land absorbs into the ground. These are two other processes that are part of the water cycle. Water that moved down a hill or mountain back into a river, lake, or ocean is called Runoff. Water that absorbs into the ground is called infiltration and becomes groundwater.
I label runoff, infiltration, and groundwater on the diagram.
Water Cycle in a Bowl
After diagramming the water cycle and discussing each step in depth, we model it in a bowl. I provide each group with a large bowl and some clay. I tell them to create a hill with the clay on one half of the bowl. As they get their hill completed, I fill the other half of the bowl with hot water (the model will not work if the water is not hot). In their notebooks I have them draw the bowl with the hill and water in it.
As students illustrate this part of the model, I circulate to each group and give them a piece of plastic wrap to cover the top of their bowl. I ask students what the plastic wrap represents in our model and they tell me the atmosphere. They add this to their illustration with a label.
I circulate to each group and place a piece of ice in the center of the plastic wrap. This serves two purposes. I ask students why I would place ice there. They tell me to cool off the water vapor like the atmosphere would cool it off. That is correct, and the reason I place it in the center is to weigh down the center a little so that as water condenses on the plastic wrap it will run down to the center and collect together there. Students add the ice cube to the drawing and write an explanation that it is representing the cooling from the atmosphere.
Groups observe their model and watch as a cloud forms on the plastic wrap. Eventually the drops collect together and fall back into the bowl. As you can tell in the video of water cycle model, the process takes some time. The cloud forms immediately but for it takes about 5 - 10 minutes for drops to collect together. While students are waiting for this to happen, I tell them to write 5 steps describing what is happening to the particle of water as it goes through the process. I call some of the ESE/ELL students (only the few that need the modification) over one at a time to verbally tell me the 5 steps and I write them down in their notebook for them. This allows me to assess their understanding and not their ability to write them. It is important for me to write them for the students as they tell me so that they are able to see the written form of what they are saying and so that they have it to refer back to when studying.
The Water Cycle Story
I place a piece of paper under the document camera titled "The Water Cycle Story". I explain to students that we are writing a story about a character named Wally the Water Molecule. We are going to tell the story of his journey through the water cycle. Each student must add at least one sentence to the story. I begin with Wally was floating along among millions of his closest friends in a great big ocean. The students add information, using the 5 key points they recorded during the model activity as a guide, and our final story ends up like this:
Wally was floating along among millions of his closest friends in a great big ocean. As they all got closer to the surface they began getting hotter and swimming farther and farther apart. Eventually they were so spread out, they began floating out of the water, up through the air.
As they moved up through the air, they began getting very cold. "Burr" said Wally, "come keep me warm!" His friends began getting closer together to help warm each other up.
"I can't see in here," someone shouted. "This cloud is so full," someone else yelled. All of a sudden they all began falling from the cloud. They kept falling for what seemed like an eternity, until...SPLASH.
Most of them fell back into the ocean where they had started. Some however, did not make it back to the ocean. Some fell in lakes, rivers, streams, or even on the ground. Wally was one that fell on the ground. He hated the ground and wanted to find more water. He worked his way deep into the ground in search of more water. He eventually came to a little pool of water under the ground where he lived happily with new friends.
The story turned out amazing but did require some guidance. For example, at one point the student whose turn it was wanted to end the story by saying "he fell back in the ocean, the end." I reminded this student, and everyone else, that the purpose is to keep it open enough so everyone has the opportunity to add to it. There were still four students left after him so I asked him to change the story so Wally fell somewhere other than the ocean. He changed it to Wally falling to the ground. I wrote each students name in the margin as they added to the story so I was able to remember who had participated and who still needed a turn. This is also a useful strategy when going back to assess understanding based on the sentence they added. The story goes pretty quickly, especially at first, so going back through it later is important.
I was surprised at how well the story turned out. They thought of things I never would have and easily kept the story going. They also covered all components: evaporation, condensation, precipitation, the ocean collects the most water, and groundwater is another place water collects besides the ocean.
Why Create a Story
Having students add information to the story allows me to assess their understanding of the process as we add on to the story. Students have the opportunity to add a line when they feel comfortable and can use their notes to help them so even the ESE/ELL students can be successful. This also helps make the connection to language arts by incorporating narrative writing into the lesson.