To obtain a better perception of earth's oceans and to understand earth's water cycle.
In earlier grades, students learn about weather, oceans, and water as separate entities. As early as kindergarten, students complete exercises such as measuring and keeping track of precipitation. In grades 3-5, students learn that water can change states: liquid water can evaporate and become a gas, and water vapor becomes liquid due to temperature changes.
This lesson starts to bring the concepts mentioned above together with a focus on the water cycle. The two-fold lesson begins with an experiment that demonstrates water evaporating and coming back down. The lesson is meant to give students a general understanding of earth's oceans. In the end, students should realize that water in the ocean evaporates into the atmosphere and comes back down as precipitation. This lesson is a good introduction to future lessons on weather and earth's climatic changes. (See the extension or the Science NetLinks lesson entitled El Nino.)
Note: Regarding the water cycle, students may have a difficult time understanding the existence of water they cannot see with their own eyes. They may think that evaporated water ceases to exist, or that it can only change into a form they can see, such as fog. (Benchmarks for Science Literacy, p.336.)
For younger students, consider having each one create a book on oceans instead of keeping a journal. As the lesson progresses, students can put each part of the lesson on a separate piece of construction paper. Where the lesson calls for diagrams, students can use paints and magic markers. At the end, have students make a cover page, then three hole punch and tie the "chapters" together.
Older students will keep a journal (or book) with two to three page sections—one section for each task. You may want to recommend that each section of the lesson start on a new journal page with a title at the top.
The following activity, called Build a Model of the Water Cycle, can be found on the Oceans Alive website.
Introduce the lesson with a question: "Do you think there is always the same amount of water in the oceans?" Write down students’ answers on the board.
Now tell students they will set up an experiment that might help them answer the question. If some students understand that water evaporates from the oceans, this experiment will be a good review for them. Divide your class into groups of four or five and provde each group with the Build a Model of the Water Cycle activity sheet. Each group should do their own experiment. Have each group read the whole activity and follow the procedure up to step four. Students should document the procedure and temperature of the water in their journals.
At this point, ask students if they think the water in the baggies will always be the same amount. Discuss this and have students predict what the outcome of the experiment will be. Have students document their predictions in their journals. You will need to wait a few hours before the water in the baggies starts to condense. If necessary, you can revisit the baggies the next day. Tell students to leave room in their journals for observations and conclusions.
Give students a short creative writing assignment. They will have fifteen minutes to write an essay that describes the journey of a drop of water. Tell students they can write in the first person as if they are the drop themselves, or in third person. Encourage students to be creative—the drop of water can exist anywhere and could feasibly travel anywhere, but students should try to describe how.
Once the essays are finished, have students put them aside. Students will have an opportunity to revise their drafts at the end of the lesson and input them into their journals.
Have students observe the baggies and talk about and record their observations. They also should write up a conclusion.
The Water Cycle
To bring the water cycle into the bigger picture, students should use their Oceans student esheet to go to and read: Looking at the Sea: The Water Cycle. In their journals, they should draw their own diagrams of the water cycle, similar to the one at this website. They also should write a paragraph in their own words to describe the water cycle. Ask students to describe how the water cycle is similar to the baggie experiment.
Fact Sheet on Oceans
Students should not only become aware of the water cycle, but also where most of the water on earth is located. Have students develop a fact sheet on oceans. They can develop this page as they use their esheet to go to and read the information at Looking at the Sea.
Getting to Know the Oceans
Now students should go to Looking at the Sea:Ocean Profiles. Instruct them to draw a very basic flat map of earth in their journals as seen on this page. They can shade in the land and label the oceans.
Once the maps are drawn, students should make four ocean profiles in their journals. They may want to use one page to profile two oceans. They can obtain information by clicking on the different areas of the online map to read about the oceans. The profiles should include ocean depths. Tell students to translate the depths into miles by dividing the number of feet by 5,280. (1 mile = 5,280 feet)
Are the Oceans Deep or Shallow?
This question presents a paradox. Though some parts of earth's oceans are up to seven miles deep, they are also a "relatively thin" layer on earth's surface. In question two, students recorded some depths of the oceans. Here, they will diagram earth as a whole, and show that oceans are part of the thin surface layer.
Have students go to Welcome to our Earth, part of the Franklin Institute website. Using this site as a reference, they should draw a diagram of the earth split open, labeling the different layers (crust, mantle, outer core, and core). They also should label how many miles thick each layer is. When they are finished, discuss the fact that oceans are only on the top layer, and that just in comparison to the mantle which is 1,750 miles thick, the ocean may not seem so deep after all.
If time allows, lead a discussion about whether or not the oceans are deep. Some students may refer to the number of miles down an ocean floor is, others may look at the big picture.
Tell each student to write his or her ideas on the page next to the diagram they have just drawn.
What Does the Ocean Floor Look Like?
Students will learn that the ocean floor is a rough terrain of volcanoes, plateaus, and trenches. Have students draw their own ocean floor across the bottom of at least two pages in their journals. In the upper portions of the pages, they can write about some of the land features and describe them.
Students can read about the ocean floor and see a diagram of it at Looking at the Sea: Physical Features of the Ocean.
Currents in the Oceans
Students will probably first think of waves when contemplating movement in the oceans, but they also should learn about currents in order to understand that the atmosphere above affects movement in the oceans. Later they will learn that these currents affect weather patterns.
When they are done reading, have them draw the warm and cold currents on the ocean maps they drew earlier in the lesson. Ask them to describe in their journals what causes currents.
Give students an opportunity to write a second draft of their essay, the journey of a water drop. They can use their journals as inspiration. What they have learned should come out in their writing. Encourage them to make the second draft more descriptive and longer. It may be a good homework assignment.
You can collect the journals to evaluate how your students responded to the assigned tasks throughout their journals. The essays should also demonstrate what sort of understanding students have gained from this lesson. Since the assignment is the "journey" of a water drop… the water must get caught in a current, evaporate, and precipitate, or even travel to the depths of the ocean.
A further exploration of the site "Oceans Alive" will broaden the scope of your students' understanding of the oceans. Here are some highlights:
Water Currents: A hands-on activity on currents that demonstrates the differences in temperature and density playing an important role in shaping the ocean currents.
Wind and Waves: A hands-on activity on waves. This activity shows that an object on a body of water with waves will not be moved laterally by the waves, but in a circular motion.
Can sunlight reach the bottom of the ocean? Not the deepest parts. Have students go to The Living Sea to learn about the zones of the ocean and what life forms are found in each zone. Students could add this to their journals by drawing the zone and illustrating some of the life forms.