Water on Earth - Liquid or Solid

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SWBAT identify where they might find liquid or solid water on earth and explain why

Big Idea

Climates vary and understanding that water on earth reacts to the climate is a way to understand why water can be found as both liquid and solid on earth.

States of Water

15 minutes

Today I am going to begin the lesson with an exploration. I am not giving students an I Can statement because I want them first just to explore what they are already familiar with but may not have really ever had to think about or explain. Students are familiar with water, snow and ice and know that when ice or snow melt they get water, but have they ever really explained the melting process or thought about the fact that water and ice and snow are the same thing just in different states? Rather than telling them that I want them to find that out, I let them explore first and try to find that out on their own.

This lesson will begin with a chance to explore the properties of water. I bring in ice, water and a teapot and a tin pie plate. 

I start by handing each student a piece of ice. I say, "can you tell me about the piece of ice you have?" I write down their observations on the easel. I let the students hold the ice until it melts. Now I ask them to describe the water that is on their desks and hands. "Can you describe the water that is on your desk?" Again I write down their observations on a second column of the easel. 

"What happened from the time you held the ice until you held the water?" (the ice melted) "Is the ice the same as the water? Why or why not?" I encourage students to think carefully about the reasons of their classmates. "Do you agree with ________?" "Why or why not?" I am hoping that students will engage in meaningful scientific conversation about the similarities and differences between ice and water. 

When the conversation has ended, I bring out the electric teapot and plug it in. I take more ice and place it on the tin pan. I ask students, "what do you think will happen when the water in the pot boils if I hold this tray of ice over the pot?" I take predictions and then demonstrate. We should be able to see the steam from the pot and then the condensation of water on the bottom of the pan, as well as the melting of the ice in the tray.

I ask students, "What do you think is happening to make the water on the bottom of the tray? Where did it come from? Do you think there is a leak in the bottom of the pan?" We discuss what they are observing and thinking. I want them to understand that water can take different forms and that the steam, water and ice are the 3 states of water. 

I introduce the terms liquid, solid and gas. I ask, "Which of the water forms that we saw are liquid?" "Which of the water forms are solid?" "Which are gas?"  I say, "all matter can exist as liquid, solid or gas but we don't usually see them because they need super high heat or super low cold in order to change. How many of you have see a wax candle melt? It goes from a solid to a liquid when it gets hot. Can you think of anything else that might change with heat or cold?" 

"So now you know that water can be liquid, solid or gas. Today we are going to think about where on earth we might find liquid or solid water and why."

Liquid and Solid Water on Earth

20 minutes

I hand each student a World Map. I ask them, "can you point to one of the coldest places on earth?  Remember that there may be more than 1 so you may not be pointing to the same place as your neighbor." I ask students to look at where their neighbor is pointing and to see if it is the same or different as the place they picked.

I point to the class world map on the wall and say, "I have several snowman cutouts. Who would like to come up and place a snowman in a place they think is cold?" I let students place the snowmen on the map until the places they pointed to on their own maps have been marked. 

"What do you notice about these places?" (I am hoping students will notice that the snowmen are near the North and South Poles or on mountain ranges.) "Why do you think they are colder than other places on earth?" (They are at the North Pole, or South Pole. It is colder way up north, etc.) "What kind of water would you expect to find in these places, liquid or solid? Why?" After students respond I ask, "What form would the solid water be in?" (ice, snow, glacier). See Discussing Choices of Snowman Placement.

Students are likely to bring up that there is snow where we live part of the year. We talk about why that might be (winter, the seasons). 

I now say, "where do you think the hottest places on earth are? Can you point to one on your map?" Again I ask them to share with someone at their table about where they have chosen. This time I bring out sun cutouts. I say, "who would like to come and put a sun where it is hottest?" I let students put a sun where they think it should go.

I ask, " Why do you think these places are hot?" (they are down south, they are on the equator, etc.) "What kind of water would you  expect to find in these places liquid or solid? Why"  I let students explain their reasoning.

Now, in order to stimulate good scientific conversation with everyone participating, I give each person two stacking cubes. I say, "I want each person to talk about why they think there are places on earth where the water outside is usually liquid or solid. Also, look at the class map, and if you think any of the suns or snowmen are in a place where they don't belong, tell why you think so. I would like each person to share at least once. After everyone has shared once, if someone wants to share another idea, or if you want to comment on what someone else has said, you can add your second cube." I check for understanding and then let the groups talk. I circulate around to listen in on the conversations and to support students who may be struggling to share by asking them questions such as, "do you think all the suns on the wall map are in the right place and why do you think they are there? Could you think of a place where the water is always frozen, how do you know? etc."

I ring the bell to stop the conversation when I can see that most people have shared and the groups are running out of things to share.

Assessing Understanding

15 minutes

"You have had some interesting discussions about where we find solid and liquid water on earth. Now I would like each of you to draw 2 pictures, one on each side of the paper. One side should show what you think it looks like where water is usually solid and one to show what you think it looks like were water is usually liquid. Remember that you are drawing the landforms, and the surroundings as well as liquid or solid water. You can't just draw ocean for water. You will need to show a landform as well. You can't just draw white for the solid water, but show what the landforms or surroundings look like. Our I can statement for today is: I can draw a picture to show where water on earth is usually liquid and one where water is usually solid. You will try to put as many details into your picture as possible. Please label your pictures LIQUID WATER, SOLID WATER." I check for understanding before handing out drawing paper. 

I give students time to finish their drawings because I want to use them to assess their understanding of where on earth you can find water as a liquid or a solid.