This is the first of four "engage" activities which students will investigate striped bass and the Estuarine Turbidity Maximum (ETM). Students will view a video illustrating the density differences between fresh and salt water. A second option is for the teacher to make or purchase a density tank from a science supply house. Links are provided in the Lesson Resources section of this page to other density activities utilizing an aquarium tank. 

Teacher Note:  This and the other three "engage" activities (Water Clarity, Striped Bass Larvae, Tidal Rhythms) all can be conducted in one class period or may be split up, as the concepts are introduced throughout the web resource. This activity takes approximately 10 minutes for explanation and video.  If you use a demonstration for explanation plan to take more time.

Objectives

• Students will be able to explain what a density current is by watching a demonstration
• Students will predict where the Estuarine turbidity maxima occurs in an estuary
• Students will examine how density layers are formed
• Students will identify what causes density currents

Materials

• Chart paper
• Video clip of density tank (scroll down to view video)
• Aquarium to demonstrate density currents
• List of references for alternative activities

Procedure

• Students can view the video or teacher can use a hands-on demo listed in the Activity Resources section.
• Begin the lesson with a brainstorming activity about water’s ability to form layers.
• Record student ideas on chart paper for all to view.
• Ask students to suggest reasons why water might layer
• Ask students if  they have any first hand experiences that would suggest that water layers. Lead the students to discover that water layers, due to density differences either caused by temperature or salinity or both.
• Follow the discussion with a demonstration of the density tank video or preform your own demonstration utilizing one of the reference activities.

Lesson Resources

• Hands-on density activity using graduated cylinders (see Density activity)
• Hands-on density activity using a density tank (see Density Driven Currents; tank building instructions included)
• Another density activity: http://www.beloit.edu/sepm/Water_Works/density_currents.html

National Science Education Standards

9-12 A: Science as Inquiry

• Understandings about scientific inquiry

9-12 B: Physical Science

• Structure and properties of matter
• Interactions of energy and matter

9-12 D: Earth and Space Science

• Energy in the earth system 

NS.9-12 F: Science in Personal and Social Perspectives

• Environmental quality