1. Hook Your Students: Where would you most like to take a family vacation?

As students enter the room, tell them to answer the question, “Where would you most like to take a family vacation?” by placing 10 ml of water into a 100ml graduated cylinder representing their destination choice for a vacation: ocean, lake, or snow/ice. Discuss students’ responses after doing the activity Where Is Water On Earth? Compare where students would like to go on vacation to the percentage of water found in that location on the Earth.

2. Review the water cycle—how water moves and is stored on Earth.

List the locations where water is found on Earth. [Water is stored on Earth in the oceans, icecaps and glaciers, groundwater, lakes, rivers, atmosphere, plants, animals, and soil.] 

In what phases (forms) is water stored on Earth? Give some examples. [Water is found in the liquid, solid, and vapor (gas) phases. Examples are: water vapor in the atmosphere, ice and snow (solid) in the polar ice caps and continental glaciers, liquid water in lakes and rivers, liquid water in the oceans, liquid water in groundwater aquifers, and liquid water in plants, animals, and soil.]

How does water move from one location on Earth to another? Show the overhead transparency of the Water Cycle that does not have any arrows or labels on it. Ask students to describe the transfer process as water moves from one location to another, in response to the following prompts:

How does water get from the atmosphere to the land surface, glaciers, polar ice caps, lakes, and oceans? [By condensation and then precipitation, the process by which water vapor in the atmosphere condenses to form liquid rain or solid snow and then falls (precipitates) by gravity to the Earth.]

How does water get from the land surface to the groundwater? [By infiltration through the soil into the groundwater.]

How does water get from the land surface to rivers, streams, lakes, and oceans? [Surface runoff directly into rivers, streams, lakes, and oceans, or infiltration into the groundwater that moves and eventually seeps into rivers, streams, lakes, and oceans.]

How does water get from groundwater to rivers, streams, lakes, and oceans? [Groundwater seeps into rivers, streams, lakes, and oceans.]

How does water get from the land surface, animals, rivers, streams, lakes, and oceans to the atmosphere? [Evaporation, the process by which water goes from a liquid to water vapor.]

How does water get from snow to clouds? [By sublimation, through which water goes from a solid (snow and ice) directly to water vapor.]

How does water get from plants to the atmosphere? [By transpiration, the process by which water is taken up from the soil by plant roots, transported through the plant where it is used in respiration and photosynthesis, and evaporated into the air through tiny openings (stomates) in the leaves to become water vapor.]

Distribute a copy of the Water Cycle diagram student activity page to each student to complete. Review the following concepts with students:

• Water is found on Earth as a solid, liquid, and gas.

• Water is found on the Earth as surface water and below the Earth as groundwater.

• Water can be freshwater or salt water. Salt water is primarily used for shipping, recreation, fishing, and as a habitat for marine plants and animals. Freshwater is far more usable by humans. (Optional: Offer one student a sip of salt water, prepared by the teacher.) Can salt water be used by humans for drinking, household uses, livestock, crop irrigation, or industrial processes? [No.]

• The sun (solar energy) is the source of energy for water evaporation, air movement (moves clouds), cooling, and condensation.

• Gravity drives “falling” water (rain and snow), runoff, and stream flow from high to low elevations.

• Water is neither created nor destroyed, but changes location, and possibly form (phase) and quality, as it moves through the water cycle.

• At any one time, most water is “stored,” rather than “moving” in the water cycle. The oceans are the storehouses for the vast majority (97.2%) of all water on Earth. Most (90%) of the water that is evaporated as part of the water cycle comes from the oceans.

3. Trace the path of a drop of water from your school to the Atlantic Ocean.

Show the map of the United States. Ask students to identify where their school is located. How does a drop of rain falling on the school parking lot reach the Atlantic Ocean? [The raindrop will run off the parking lot and travel overland as runoff into a stream, river, or lake; seep down into the groundwater; or go down a storm drain and empty into a river or lake. From there, the drop would eventually reach the Great Lakes (be sure students can describe exactly how this will happen). Trace the movement of the drop of water through the Great Lakes, the St. Lawrence Seaway, to the Atlantic Ocean.] How can that same drop of water return to Michigan? [Through evaporation or sublimation, and then precipitation.]

Outdoor Connection

Follow a Drop of Water

Place the students in groups and have each group draw a map of the Great Lakes basin in the parking lot using sidewalk chalk. Label each of the Great Lakes, the states and provinces, and the St. Lawrence Seaway. Have the students trace the path of water on their map using arrows starting at the school parking lot and ending in the Atlantic Ocean. Provide the U.S. map or Great Lakes Watershed map to check their work.

Water Cycle Scavenger Hunt

Take students outside to look for evidence of the water cycle, such as: evaporation, runoff, infiltration, transpiration, etc. Give each pair of students a list of items to look for (see student page). Ask students to share what they found.

4. What percentage of Earth is covered with

water?

Paper plate activity - Part 1 (Optional): 

Distribute one blue and one green paper plate to each group or each student. Tell students to make one cut on each paper plate from the edge to the center. Fit the two plates together so that rotating them exposes more or less of the blue “pie fraction.” Tell students to adjust their plates in order to show how much of the Earth is covered with water. Ask students to hold up their pie plate fraction to compare with other students’ estimates.

Play a game of Globe Toss with students.

Assign one student to count tosses and another student to record the number of “water” and “land” responses on the board or overhead projector. Tell students to stand in a circle and take turns throwing the inflatable globe a total of 100 times. When a student catches the globe, he/ she must call out “water” or “land” depending on which their right thumb is touching when the globe is caught. Calculate the percentage of times the students’ thumbs touched land or water.

Because approximately 70% of the Earth is covered with water, thumbs usually touch water an average of 70 times out of 100 throws. When fewer than 50 throws are used, results are less reliable. Once the activity is done, have a student taste the salt water. Discuss the taste—would they want to use this water for drinking and cooking? Having 70% of the Earth’s surface covered in mostly salt water is great for transportation and recreation, but not for direct human use.