# Lesson: Teaching convection currents with lava lamps

David Kujawski Bird Middle East Walpole, MA
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### Lesson Objective

YWBAT: 1) Explain the formation of convection currents by modeling their creation with a lava lamp

### Lesson Plan

Overview: This lesson uses students' prior knowledge and experience with density to determine how a lava lamp works.  Students are then able to see that a lava lamp is a model of what actually happens in Earth's mantle.  I start my plate techtonics unit by talking about density and convection currects because they're the driving force of plate movement.

Do Now: Observe the lava lamp and record what you see on a piece of paper

Discuss observations: Some of the goo moved upwards, while some of sank.

Next: Ask students to volunteer what they remember about density.  Write what they remember on the board.

Next: Review density by completing http://science.howstuffworks.com/framed.htm?parent=question36.htm&url=http://www.nyu.edu/pages/mathmol/textbook/density.html

Calculate the density of each block at the bottom of the site as a class.  Then ask which block is denser and have them explain why.  Answer: the one that has more mass per volume is denser, as shown in the calculations.  Density of Block I is 2.66 g/mL or g/cm2 and the density of Block II is .85 g/mL or g/cm2.  Therefore, Block I is more dense.

Next: Ask students to recall what happens when you mix water and oil.  Demonstrate mixing the two liquids to the class. Discuss why the oil floats and the water sinks.  Answer: the water must be denser than the oil.

Recall prior knowledge:  Ask--What role does heat play on atoms and molecules?  Answer: When molecules are heated they spread out and when they cool they get closer together.

Group work: Have each group of 3-5 students try to draw a picture explaining how a lava lamp works (Give Lava Lamp Worksheet 1).  The worksheet includes the parts of a lava lamp: 2 different liquids, an enclosed capsule that holds the liquids, and a heat source at the bottom of the capsule.

Ask students to draw a picture and explain in detail how the lava lamp works.

Next: Have students share their ideas.  Ask questions that can direct them in the right way without giving them the answer.  Your goal should be to establish the following:

1)      Heat makes atoms and molecules spread out

2)      Less dense things rise, while more dense things sink

Next: Have students take out their notes and worksheets on Earth’s layers.  Ask them to explain how the lava lamp is a model for what happens in the mantle.  Field student responses and then show them the Lava lamp picture worksheet.  Have students draw and label the image on the board into their notebook.

### Lesson Resources

 Density review website 3848 LAVA LAMP picture worksheet.doc 1,784 Lava lamp worksheet 1.doc 1,534