FOCUS: The Earth’s water is in oceans, lakes, and rivers, in the atmosphere and underground, inside plants and animals, and frozen in glaciers. The water present today is the same water that has been here for millions of years, though it is constantly in motion, moving from place to place. Water evaporates into vapor, condenses into clouds, precipitates as rain or snow, and transpires through plants as it moves between atmosphere and land, over and over again in a cycle that is powered by the sun and essential to living things.
Objective: To begin to explore and ask questions about water.
Give each small group of children a bucket of water, a bowl of ice, some cups, and some spoons. Allow them to explore the materials, and ask what they notice and wonder about water.
Materials: basin of water, spoons, cups, and ice, set for each group; optional: funnels.
HOT, COLD, AND FROZEN (Grades 3-6)
Objective: To compare the density of water at different temperatures.
Ask the children what happens to air when you heat it up. (It gets lighter and rises.) Would water get heavier or lighter when heated? Ask for ideas about a way that you could test this.
Hot Water Rises: Fill a quart-sized glass jar with cold water. Fill a small bottle or vial with hot water. Add a drop of food coloring to the hot water. Using tongs, carefully lower the small bottle into the large jar. Why does the hot water come out of the bottle and swirl upward? (Hot water is lighter than cold water.)
Cold Water Sinks: Now ask how you might test this in reverse. Fill a quart jar with hot water. Fill a small bottle or vial with cold water and add a drop of food coloring to the cold water. Gently lower it into the jar of hot water. Why does the cold water stay inside the vial? (Cold water is heavier than warm water.) Why does it start to come out after a while? (It warms up because it’s in a large jar of hot water.)
But Ice Floats: Now ask them about ice. It is colder than cold water. Will it sink or float in a glass of cold water? Give each small group an ice cube and a cup of water so they can experiment. Why does the ice float? (Ice is lighter than cold water.) How does this affect the ice on our lakes, ponds and streams in winter? (It stays on top of the water instead of sinking to the bottom, so we can skate or go ice fishing on it, and the fish and frogs can survive in the 39° F water at the bottom.)
Materials: two quart-sized clear glass jars, two small clear glass vials or bottles, cold water, hot water, food coloring, tongs, ice cubes, cups.
STICKY WATER ACTIVITIES
Objective: To observe examples of cohesion, adhesion, and surface tension in water.
There are three parts to this activity:
Drops on a Penny: Give each pair of children a penny, a cup of water, an eyedropper and hand lens. Ask the children to count how many drops of water they can put on the penny before it overflows. Use a hand lens to look at the water as it piles up on the penny. What is its shape? (Like a flattened globe.) Why does the water pile up instead of spilling over at first? (Because of surface tension: the molecules of water are attracted to each other like magnets and so hold together.) Why does it spill eventually? (When it gets too heavy, the pull of gravity becomes greater than the force of attraction between the water molecules)
Drive the Drop: Provide each pair of children with an index card on which a squiggly line with starting and ending points has been drawn. Place a piece of waxed paper over the card. Now place a few drops of water near the starting point on the card. Have a child use a toothpick to combine them into one and then pull or push the water drop along, following the line to the finish. Why does the water drop stick to the toothpick? (Water sticks to itself and to some other materials, like wood and glass, as well; notice it doesn’t spread on the wax paper surface.)
Floating Fleet: Give each pair or small group of children a dish of water, paper clips, and a fork. Have the students try to float a paperclip. (Carefully sliding it off a fork works well.) Why does it float? (The water molecules are attracted to each other like magnets and can hold together even under the weight of a paperclip.) How many paperclips can a team float at one time?
Optional: As a demonstration, add a single drop of detergent to a dish with a floating paperclip. Why does the paperclip instantly sink to the bottom? (The detergent breaks the surface tension, letting the paperclip fall through) Note: it is very hard to reuse a cup once it has detergent in it.
Materials: water, pennies, eye droppers, hand lenses, 3×5 index cards, waxed paper to fit over the cards, toothpicks, small cups or dishes, paperclips, forks, dish detergent.
Objective: To use a model to understand how water travels through plants by capillary action.
Have children work in small groups at tables. Place a dish of water in the middle of each table and give the students each a strip of paper towel. Have each child use a water-based marker pen to place a dot of color about two inches from one end of the paper strip. They may want to put two different colored dots side by side.
Now have the children dip the end of the strip about a half an inch into the bowl of water and hold the strip up so that it is vertical. Watch the water climb up the strip. What happens when it gets as high as the colored dots? (The color spreads as it dissolves in the rising water.) Why does water move upward, against the pull of gravity, in a strip of paper? (Capillary action – water is drawn upwards inside tiny tubes or pores in the paper by adhesion, because it is attracted to the paper, and by cohesion, because water molecules stick together and pull each other along. The movement of ink shows how minerals are pulled along too.) How is capillary action important in the water cycle? (It is part of how water moves through plants.)
Ask the children for ideas of how they could use capillary action to move water from the dish to an empty bowl. Place a dry bowl next to the dish of water. Put the dry ends of the paper towel strips into the dry bowl, leaving the other end in the water. Ask the children for their predictions about whether the bowl will stay dry or whether the water will be transferred into it. Check the bowl after five or ten minutes. Where did the water in the bowl come from? Did the ink move into the bowl as well?
*Optional: A day or two ahead of time, place a stalk of celery or a white carnation flower into a vase of water containing a few drops of food coloring. Or, split the stem of the carnation lengthwise and put each half into a different colored water solution. Cutting the flower stems very short and leaving them out of water for a few hours beforehand speeds up the process. Look for color change in the leaves of the celery or leaves and petals of the carnation. How did this happen? (The water is drawn up into the stem by capillary action and evaporation from the leaves.) Place a plastic bag over the plant. Look for water droplets (condensation) inside the bag. Where did this water come from? (It was transpired by the plant – it moved up through the stem and then evaporated from the leaves.) Why is this water clear instead of colored? (The water evaporates but not the dye.)
Materials: for each table: a small dish of water; empty bowl, strips of paper towel cut in one-inch widths (at least one per child); water-based color marker pens, a few at each table; stalk of celery or long-stemmed carnation, jar of water, food coloring.
INTO THE AIR AND BACK
Objective: To use a model to observe evaporation, condensation and precipitation in the atmosphere.
How can heating and cooling move water into the air and back again? We can see this with a simple demonstration.
Into the Air (evaporation): Heat about a quart of water until it is steaming. Place a lasagna or brownie baking pan on a table or floor. Pour in the hot water until it is about half full. Why does the steam seem to disappear as it rises from the hot water? (It evaporates – turns into invisible water vapor.)
Cloud-Forming (condensation): Now, hold up a similar-sized clear glass baking pan to show the children that it is dry. Have a few children feel it and notice that it is cool to the touch. Invert this pan over the top of the pan of hot water. Have the children watch the clear pan closely to see what happens. Why do water droplets appear on the underside of the glass? (Steam from the water rises and contacts the cool surface of the upper lasagna pan which makes it condense into droplets of water.) Why do clouds form in the sky? (When it hits a cold air mass, water vapor in the air condenses into millions of tiny floating water drops. We see this as a cloud.)
Raining (precipitation): Notice how the droplets combine and then eventually drip back into the pan. What happens in a rain cloud? (Water droplets bump into each other until they are too heavy to float in the air and then they fall to the ground as rain.)
Materials: one quart of very hot water, two similar-sized baking pans, at least one of clear glass.
PUPPET SHOW “Do Drop In”
Objective: To visualize a water drop’s journey through the water cycle.
Perform the puppet show, or have a group of children perform it for the class. Afterward, ask questions to review the key details and vocabulary in the story. With the children’s help, list the different places where water is found on the Earth. (Air, oceans, glaciers, plants & animals, groundwater, rivers, lakes, wetlands.) How did Willy Water Drop move from place to place?
Materials: puppets, script, props, water mister.
Objective: To model the movement of water through the water cycle and the varied routes that it can take.
Ahead of time, set up six stations outside using buckets or flower pots as markers. Label the six stations to represent places where water is found on Earth: Glaciers, Lakes and Rivers, Groundwater, Air, Oceans, and Plants and Animals. Place an opaque bag with labeled game tokens in each bucket. Use the chart below to determine how many of each kind of game token to put in each bag. Finally, place a marker pen at each station, using a different color for each one. Explain to the children that they are going to pretend to be water drops traveling through the water cycle. At each station they will get a chance to mark in a box on their passport and select a token from the bag that will tell them where their water drop goes next. Begin by sending children to stand at one of the six stations so they are equally divided among them. Children must stand in line at their station. At your signal, the first child in each line can color in a square on their passport and then pick a token out of the bag. They must look at the token to find out their next station and then put it back in the bag. Then they can go to their next station and get in line. The passports provide a record of their travels through the water cycle. Keep going until the passports are beginning to get filled up.
Afterward, have the children look at their passports and count how many times they visited each station. Add up the totals for the class. Which station got the most visits? (Usually oceans.) Which got the least?
Game tokens at each station:
Ocean Station: 7 oceans, 3 clouds
Glacier Station: 3 oceans, 1 clouds, 4 glaciers, 1 lakes & rivers, 1 groundwater
Groundwater Station: 3 oceans, 1 clouds, 2 lakes & rivers, 2 plants & animals, 2 groundwater
Clouds Station: 5 oceans, 1 clouds, 1 glaciers, 1 lakes & rivers, 1 plants & animals, 1 groundwater
Lakes & Rivers Station: 2 oceans, 2 clouds, 3 lakes & rivers, 1 plants & animals, 2 groundwater
Plants & Animals Station: 3 oceans, 4 clouds, 2 plants & animals, 1 groundwater
*Optional: instead of the marker pens, place a dish of about 50 colored beads at each station, a different color for each. Give each child a pipe cleaner, bent over at one end, and have them thread a bead onto it at each station. Afterward, form the pipe cleaner into a bracelet.
Materials: six buckets or flowerpots, rocks or gravel to keep buckets from tipping or blowing around, Station Labels, six opaque paper or plastic bags, game tokens labeled as in the chart above, a different color marker pen for each station (e.g. blue, aqua, brown, gray, purple, green), Water Journeys Passports, one per child; optional: six dishes, each with different colored beads (about fifty beads per dish) and one pipe cleaner per child.
UPPER GRADES CHALLENGE: How Much Is Fresh? (Grades 5-6)
Objective: To use a model to illustrate how much of the Earth’s water is fresh water, and how much of that is available for living things.
Show children a globe and ask where most of the water is found. (In the oceans.) Since most of the Earth’s water is in the oceans, most of it is salt water. Where is the fresh water? (In lakes, streams, underground, frozen in glaciers and icecaps.) Ask for some estimates about how much of Earth’s water is salt water. (In fact, ninety-seven percent is salt water.) Hold up a 100ml graduated cylinder filled with water, and explain that this cylinder represents all the water on Earth. Have children work with a partner and give each pair a How Much Is Fresh sheet. Have them figure out how many milliliters of water are salt water (97 ml.) and shade in that portion on their diagrams. How many milliliters are fresh water? (3 ml.) However, two-thirds of the fresh water is frozen in glaciers and the polar icecaps where it’s not available. Have them calculate how many milliliters of water are frozen. (2 ml.) Now ask them how many milliliters of fresh water are left for plants and animals and all our uses. (Only 1 ml.)
To model these amounts, pour out 3 ml. of water into a clear container to represent all the fresh water on Earth. Then pour 1 ml. from that container into a second clear container. This small amount represents all the fresh water that is available for living things, including ourselves. Ask children to think about some of the ways we use water. What are some ways we can conserve and protect this vital resource?
Materials: a globe, one 100 ml. clear graduated cylinder, two small clear plastic containers, How Much Is Fresh sheets, one per child or pair of children.
PICTURE HOW WATER MOVES AROUND (Grades 3-6)
Objective: To draw a model showing parts of a water cycle on Earth.
Have children work in twos or threes. Ask them to consider that water in any particular place came from somewhere and will go somewhere. An example: the water inside popcorn kernels that makes it pop came from rain that fell on a cornfield, soaked into the ground, and was taken up by the roots of a corn plant. The next place that water in the popcorn will go is into somebody’s mouth. Give each group paper and pencils, markers, or crayons and one of the prompts listed below. Your water is:
- in a puddle in the schoolyard,
- in a brook in a forest,
- in a snowflake on a spruce tree,
- in some wet laundry,
- in an icicle,
- in a dewdrop on a blade of grass,
- in a sink full of dirty dishes,
- in a wave on the beach,
- in a mosquito,
- in a rose petal,
- in maple sap,
- in the ground in a garden,
- in a droplet in a thundercloud,
- in a swimming hole,
- in the ice on a river,
- in a milkweed leaf
Ask the children to think about and discuss how the water might have gotten to their location and where it will go next. Have each group draw a picture showing the place in their prompt and two to three additional places where their water could have come from and/or go to and how it would get from one place to another. Make suggestions if they get stuck.
Another option is to take the children outside and send each team to a different part of the playground. Have them imagine what might happen to a raindrop if it falls at their location. Afterward, call the teams together and have each group describe their water drop’s travels in the scene they’ve depicted.
Materials: for each team: Picture How Water Moves Around prompts, clipboards, paper, pencils, crayons, colored pencils or markers.
JOURNAL ACTIVITY AND CLOSING THOUGHTS
Objective: To think about water in our landscape.
Have the children think about a watery place they like to visit – a stream, pond, puddle, beach, or other spot. Recall how the place feels – cool, hot, sandy, sunny? What sounds are common there? What smells do they remember? Then write a story or draw a picture of spending time in this special place. Afterwards, in small groups, have children share their journal entries.
Materials: science journals or clipboards and paper, pencils, markers, colored pencils or crayons.
SUGGESTED OUTDOOR ACTIVITIES
Water Journeys, How Much Is Fresh?, Picture How Water Moves Around, Journal Activity (weather permitting)
A STEP BEYOND
Evaporation Action: To investigate the importance of wind in evaporation, give each team a fist-sized rock on a paper plate and a paper or cardboard fan. Place a similar rock away from where the children will be fanning their rocks to serve as the control. Spray rocks with the water, giving the same number of pumps for each rock, including the control. At your signal, have everyone fan their rocks until they see that they are dry. Where did the water go that was on the fanned rocks? (Evaporated into the air.) Compare to the control. Why do the rocks dry faster when they are fanned? (Moving fresh air over the rock makes evaporation happen more quickly.)
Molecule Dance: Have children pretend to be molecules of water and act out the way they slide past each other. Open a door and let the water “pour” out of the opening. Or act out the change in bonding as water changes from solid (ice) to liquid (water) to gas (water vapor).
Water Cleaner: As a long term project, set up a water cleaner in the classroom. Put dirty water in a dishpan, and set an empty Mason jar in the center. Cover the whole set-up with plastic wrap. Add a stone on top of the plastic, directly over the Mason jar. Water will evaporate, condense on the plastic wrap, and drip off the plastic wrap at the lowest point, directly into the jar. Is the water in the jar clear or cloudy? (Clear, because evaporation is an important cleansing part of the water cycle.)
Urban Runoff: With older students, discuss what happens to rainwater in the city. Where does it go and what problems are created when much of the ground is covered with pavement or buildings? What pollutants might be picked up as rain washes over city streets? (In rural areas the ground itself acts as a filter to contain harmful substances until they can break down. Some cities have sewer systems and treatment plants to clean run-off before it reaches rivers and streams.)
Water Cycle in a Bag: Give each child a small plastic zipper-close bag which they should label with their name or decorate with sun, sea, or cloud. Pour in a small amount of water (about two tablespoons), being careful not to splash the sides of the bag. Have the children tape their bags to a sunny window. In a few minutes, they should start to see condensation inside the bag and then raindrops that slide down the sides.