Oceans and Salt Content (science activity)
"Seeing Sea Salt"

Prior knowledge: Students will have been exposed to the concept of evaporation in the desert unit.

Objectives:

• Students will learn that salt is in ocean water, even if we can't normally see it.
• Students will perform an experiment (procedural goal).
• Students will observe and record the data from the experiment (procedural goal).
• Students will work in cooperative group.

Materials:

• 2-cup measure
• hot tap water
• 1/4 cup measure
• salt
• spoon
• pie plate

Procedure:

1. Introduce the word "salinity" to the class as the amount of salt contained in the ocean water. Is the ocean salty? How can we tell? Can you see the salt? How might you set up an experiment to find out if a sample of ocean water had salt in it?
2. Tell them that we are all a team of scientists on a research boat, conducting several experiments and research projects to learn more about the ocean environment and the life that lives in it. I am the ship captain and Mrs. Rainer is my co-captain. We are all part of the same team of scientists. Within this team, however, we have smaller research crews. As the captain, I have divided up the ship already and assigned one of the people in each group to be the crew leader. (Point to duty definitions on a chart.) The crew leader must make sure that everyone does their job correctly. You will report directly to me if any difficulty arises. At the end of each experiment, I will collect a participation report from the crew leaders. One person will be the record keeper, in charge of keeping accurate experiment records. You, too, will have forms to fill out. Your team will help you answer the questions. Your job is to simply write these down neatly and hand them in to me. One person will be the materials manager, in charge of getting the materials to the table and putting them back when finished. And finally, the other one or two will be the experimenters to actually perform the experiment. They are the only ones to touch the materials once the materials are at your desks, unless they specifically ask for your help. I expect, however, that they will be asking for your help often. It wouldn't be in the spirit of teamwork if they did it all by themselves.
3. Call out crew names from prepared lists. Have them sit together. Hand out the forms for the different roles.
4. Before we can look at the life forms, or the plants and animals in the ocean, we need to know a little about what the ocean environment is like. Why would we need to know about the environment first? (It determines what can live there.) We are going to all do the same experiment on ocean water.
   • What are the benefits of having several crews perform the same experiments?
   • What is different about the water in our sink and the water in the ocean?
   • If we were to take a handful of ocean water in our hands, could we see the salt in it?
   • How do we know it is there?
   We are going to do an experiment to see if we can see the salt in the water.
5. Have materials person pick up the materials.
6. Have one of the group members from each group put the pie plate on the heater. At their desk groups, have the experimenters (and help) pour 2 cups of hot water into a container, then pour in 1/4 cup salt. Stir the solution until the salt dissolves. Then pour the solution into the pan on the heater.
7. Each student should have an observation chart marked for each day of the week. Have everyone draw and explain what they see in their pans. Make an entry once a day for a week.
8. At the end of the week, have the crews meet and try to explain what they think happened. The recorder will write down some thoughts to share with the class. Have the leader share their crew's thoughts with the class. Discuss the statements and clarify that when the water was heated, it evaporated, but all of the salt was left behind. What do you think would happen if we added water again and stirred? Have them discuss this question in their group and record their answers on the group record sheet. Discuss as a whole class. Sum up: So can there be salt in water even if we can't see it? YES!

Evaluation:

1. Collect the crew discussion notes. Listen to the team discussion. Do they unanimously agree at the end that salt can be in water even if we can't see it?
2. Did the experimenter and helpers complete the experiment? (watch them)
3. Collect individual student charts. Did they complete the page daily?
4. Did every student do their job in the group? Did any dominate the group? Collect the crew leader's report.

Extensions/ Reteaching Strategies: