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Teacher Resource Experiential Science 30—Freshwater Systems Activity 2 Modelling Convection Currents Time • 1 class period Activity Type • lab • chapter project • research team S T U D E N T B O O K P. 36 Materials and Equipment • Each research team needs: Bunsen burner or alcohol lamp; straw or glass tube, approximately 150 mm long × 3 mm internal diameter; ring stand; water; potassium permanganate (VII) crystals (KMnO4); 600 mL heat-resistant glass beaker; video camera Teaching Suggestions • If materials for this activity are not available, there are other ways to model convection currents. Instead of using potassium permanganate, for example, place ice cubes made from water heavily dyed with blue food colouring into warm water. • Although it is preferable for students to experience the convection current firsthand, there are demonstration videos on the internet (use “convection current video” as a search term to find examples). • For an open response activity, have research teams design their own models to demonstrate convection currents. Be prepared to discuss modifications or other ideas. You might provide students with a list of materials, for example, some of those listed for this activity: the beaker, glass tube, Bunsen burner, ring stand, water, and potassium permanganate. Or you might bring alternative materials into the classroom. You might invite each group to perform their demonstrations and have a class discussion about what worked and what did not. • After completing this activity, brainstorm how convection currents are apparent in students’ everyday lives (for example, cloud formation, winds, ocean currents, water boiling in a kettle). • This is an opportunity to discuss with students how simple models can help scientists better understand more complex issues. Discuss with students how this activity can be used to help explain the processes of plate tectonics. Encourage students to put their understanding of plate tectonics into their own words. Procedure—Expected Results 4. The potassium permanganate will start to dissolve right away and turn the water purple at the bottom of the beaker. As the contents are heated, purple water will rise to the surface creating a purple vertical column of fluid, move along the surface horizontally where it will cool, and sink, thereby modelling convection currents on a small scale. When the heated beaker is viewed from the side, and the potassium permanganate is situated at the side of the beaker, the current will flow along the top of the water’s surface in one direction, away from the heat source. 5. When the heated beaker is viewed from the side, and the potassium permanganate is situated in the centre of the beaker, the current will flow along the top of the water’s surface in two directions, away from the heat source towards both sides. Chapter 1 Plate Tectonics and Volcanoes Reflections and Conclusions—Suggested Answers 1. The coloured water in both cases follows a circular path. The path rises from the heat source towards the surface, moves along the surface, then descends as it cools, eventually flowing towards the heat source to replace the water that was rising. The only difference is that, in step 5, the heat source in the centre creates a convection current on either side of the heat source. 2. Answers will vary, but should summarize the relationship as follows. The Earth’s giant internal convection current is the driving force of plate tectonics. The less dense, hot magma rises towards the surface where it travels laterally and cools, becoming more viscous and dense, and then sinks, continuing the cyclical process. The friction between the convecting magma and crust causes the plates to travel and collide with other plates, creating geologic features such as mountains and volcanoes. 3. Answers will vary, but this model supports the theory of plate tectonics because the path of the coloured water is such that the hot, coloured water rises up from the bottom—just as magma does. At the top of the beaker, the coloured water moves horizontally along the surface—just as magma, cooled at the surface, is carried by the convection current along the surface of the Earth. The coloured water at the top cools and then sinks, because the cooler water is denser, just as portions of the Earth’s crust descend below other plates. Essentially, the movement of the coloured water follows the same general pattern as the Earth’s crust, only on a much smaller scale. This is crucial because the giant internal convection current in the mantle has enough energy to move whole continents, making mountains and valleys, and divide oceans. 4. Make sure that students store their videos for inclusion in their chapter projects. EVIDENCE OF PLATE TECTONICS S TUDE NT B O O K P P. 3 7 – 4 4 • To introduce this section and assess prior knowledge and experiences: §§ Ask your class open-ended questions such as: What evidence of geologic activity have you seen or experienced? and What stories have you heard from Elders regarding earthquakes? §§ Provide mapped examples of geologic activity in the Northwest Territories to help prompt responses and invite the class to write down possible explanations for why earthquakes occur in specific areas. At the end of the section or chapter, have students review and revise these explanations, based on what they have since learned. • Students may find it useful to make a list or table of the evidence for the theory of plate tectonics that includes the resulting geologic activity (earthquakes, volcanic eruptions, geothermal activity), lateral continuity of rock strata, and sea-floor spreading. Encourage them to add subheadings and examples, notes in point form, and graphic organizers. • To capture students’ interest, post a map of Earth’s tectonic plates on a wall and have them consider the relationship between plate boundaries and earthquakes, volcanoes, and geothermal activity. Case Study—Oral Accounts and Art Point to an Earthquake S TUDE NT B O O K P. 3 8 • Discuss how oral tradition has supplied scientific evidence for earthquakes and tsunamis. Teacher Resource Experiential Science 30—Freshwater Systems • This is an opportunity for students to reflect on Traditional Ecological Knowledge and how geologic processes may have affected peoples in the past. • Encourage students to share local stories or narratives of indigenous peoples from around the world about how they survived earthquakes and tsunamis.