Investigating Currents (Garry Joseph)

Title: Investigating Currents (from GEMS OSS Lessons 1.7 and 1.8)

Student groups investigate currents in 9 different model oceans around the classroom. At each station, students observe and record how different temperatures and salinities move in the model oceans. In a follow-up lesson, students make sense of the results to learn how differences in the density of water can cause water to move in currents in the ocean.

Principle(s) Investigated: As denser water (colder and/or saltier) sinks and displaces water below it, the less dense water (warmer and/or less salty) is forced to rise to the surface. This is one way currents can form. Currents spread heat energy throughout the ocean.

Standards : Middle School: Earth's Systems

Materials:

Blue ice cubes

Bag of ice

9 tanks (1.5 gallons)

blue, red food coloring

3 cups salt

4 plastic cups (1 oz)

2 clear plastic cups (9 oz)

9 paper cups (8 oz)

8 pushpins

9 binder clips

9 trays

blue and red pencils

water: hot, cold, room temperature

For students: 2-page worksheet, “molecule cards”

Each tray will have:

1 tank of water

1 paper cup

1 pushpin (except #3)

1 spoon (except #3)

1 binder clip

1 red pencil

1 blue pencil

1 blank sheet of paper

1 directions sheet (laminated or in plastic bag)

Procedure:

A. Introducing the Investigation

1. Define currents: Ocean currents are huge amounts of water flowing in one direction over time and a long distance. Flow of a river is another kind of current. There are also air currents- wind that blows consistently in the same direction.
2. “Turn and Talk” to a partner about what a current is, whether they have ever experienced one in a pool, river or ocean, and what it felt like to be in a current.
3. Show slide of guiding question:

4. Each station is unique and has its own directions to follow. The first group that goes to the station is the setup group- they will create the current.The other groups that stop by that station will observe what happens after the currents have been flowing. Observations are to be recorded with words and a drawing.

• At the first station, carefully follow the directions on the sheet. Place the blank sheet of paper under the tank so everyone can better observe the results.
• Leave the currents alone once they are set up. Do not disturb or stir the water in your tank.
• Food coloring is what allows you to see if there is a current and what direction it is moving. Food coloring stays with whatever kind of water it’s mixed with. If you see the blue ice cubes melting, you can follow where the melting water is going by watching where the blue color goes.
• Food coloring must stay at the front of the room. Do not add more food coloring than the directions state.
• When a group finishes its first investigation (the current is set up and all members have recorded results), the group may move to another station. Don’t go to a crowded station and don’t go to a station where the first group has not yet finished setting up and recording results.

7. Demonstrate results in a drawing: use colored pencil to show the way colored water travels. Draw arrows to indicate the direction the colored water is flowing. The colored pencils can also be used to show the different colored layers that may form. Quickly make an example sketch on the board to show how to record results.

B. Making Predictions

Class predicts current in Model Ocean #1. “This tank contains room-temperature water and the cup, with a pushpin stuck in the side, will have colored hot water in it.”

Talk in your groups about what will happen when the pushpin is removed. “Where will the colored hot water go? Will it flow along the bottom of the tank, across the top, or will it just flow everywhere?” Discuss with the group for one minute.

Students record predictions on their worksheet.. Make and record predictions for #4 (room temp fresh + room temp salt) and #8 (room temp salt + cold salt). Have volunteers share their predictions, and as they do, quickly sketch what they describe, and ask if the drawings accurately capture their predictions. (You could do more predictions but that will take more time). (You can also demo a model using a document projector).

C. Investigating

Everyone in the group should share the jobs and discuss ideas and questions. Students don’t have to visit all the stations. Circulate and remind students to write down predictions for their first station. Challenge students to use the words molecules and density in their explanations.

When a station is free, go as a group and carefully observe. Visit as many as time allows, give a 3 minute warning to complete last station.

Next Lesson: Students reassemble into mixed groups to explain to other pairs of students what happened with the currents at their first station. Watch a video of density flow model demonstrations and animations of the 9 model oceans, showing how convection currents move warm and cold water in the world’s ocean.

Student prior knowledge: What prior concepts do students need to understand this activity?

Explanation:

Content: The Ocean as a Heat Reservoir, Density and Movement of Ocean and Air Currents, Water Cycle.

Practices: Making explanations from evidence, using models

Vocabulary: absorb, atmosphere, climate, condense/condensation, currents, dense/density, evaporate/evaporation, evidence, heat energy, heat reservoir, matter, model, molecule, precipitation, water cycle, water vapor.

Videos:

Questions & Answers: Give three thought-provoking questions and provide detailed answers.

Applications to Everyday Life: Explain (don't just list) three instances where this principle can be used to explain other phenomenon.

When students make explanations and discuss results in the next lesson, they sort "molecule cards" to explain the way the currents moved. Student explanations are more important than the "right" answers. The two cards with the fewest molecules represent gases. The card showing two types of molecules represents a solution, such as salt water. The other three cards represent water molecules at different temperatures.