density, salinity, convection, convection current

The students will learn about how temperature and salinity affect ocean currents

60-90 minutes

1 Ocean apparatus        
2- Rubber stoppers, one-hole         
Hot plates/pots
2 Plastic vertical tubes         
2- Cube-shaped plastic containers     
Protective gloves
2 Plastic Cross-tubes         
2- 500 ml glass beakers                
Thermometer              
Sodium Chloride (table salt)        
Water    
Ice                
Food Coloring     (30ml red; 30ml blue)
Vaseline (optional)

Assembling the Apparatus                         
Procedure:
1.Assemble the Ocean Apparatus as shown in the illustration.
2.Place a vertical tube in the center opening of the cube-shaped container. Gently press down on it until it is tightly fitted into the center of the container.  Repeat the step with the other tube and the cube-shaped container.
3.Insert a one-hole rubber stopper halfway onto each end of the 2 cross tubes.  The rubber stoppers may be coated with Vaseline to make it easier to insert the tube into the rubber stopper.  
4.Connect the cross tubes to the vertical tubes.  Place one end of the cross tubes with the rubber stopper into the lower drilled hole on the vertical tube.  Twist in the rubber stopper so that it is securely placed into the drilled hole.  Repeat this step and place the second cross tube into the top drilled hole on the vertical tube.  A coat of Vaseline may also be applied to the outside of the rubber stoppers to facilitate the insertion into the vertical tube and prevent any water leaks.   
5.Connect the other end of the cross tubes to the corresponding drilled holes on the second vertical tube.  Gently push in the rubber stoppers so that they are tightly connected to the vertical tubes.
6.At the end of each investigation, be sure to rinse all components of the Ocean Circulation Model to prevent the plastic from being stained by the food coloring solutions used. Allow the apparatus to air dry.  Do not use alcohol or any harsh detergents on the apparatus.  Wipe Vaseline with paper towels.

Activity: Convection Currents and the Effects of Temperature on Circulation
Assignment
1.What general temperature is the red colored water?  _____________
2.Which tube contains the red water? Circle one: upper or lower
3.If this model were actually the Earth’s oceans, where would the red water have originated? ______________________
4.Would the red water be (circle one) surface water or deep water?
5.What general temperature is the blue colored water? ______________
6.Which tube contains the blue water? Circle one: upper or lower
7.If this model were actually the Earth’s oceans, where would the cold water have originated? ______________________
8.Would the blue water be (circle one) surface water or deep water?
9.Describe in two or more sentences the movement of the water currents and relate this to ocean currents.



10.What is the difference between surface currents and deep currents?



11.Which is more dense (circle one) cold or hot water?  Explain.


12.What is the rising of deep cold currents to the ocean surface called?

Activity:  The Influence of Salinity on the Density of Water
Procedure:
1.Assemble the ocean model apparatus as outlined in Activity 1.
2.Fill vertical tubes ¾ full with tap water at room temperature.
3.Make saturated salt water (this may be done prior to class) in the following manner:
a.Measure 500 ml of warm water.
b.Add salt until the solution reaches saturation (the point at which no more salt will stay in solution).
c.Add blue food coloring to the salt solution  
4.Fill the remaining portion of the tubes with the colored saturated salt water by pouring it through the vertical tube on the left.
5.Observe what happens to the salt water.
6.Answer the questions that follow.
7.At the end of the activity, be sure to rinse all components of the Ocean Circulation Model with tap water.  Allow it to air dry.         

Assignment:
1.What is more dense (circle one) blue water/salt water or clear water/fresh water?
2.How do you know this (from #1)?


3.What happens to the salt water and fresh water after several minutes?


4.How would you define density?


5.How are surface currents and deep ocean currents different?


6.How do you think the variation in density at different depths of the oceans affects the diversity of life forms that live there?



7.How are deep ocean currents important to sea life?


8.List two ways that water can increase in density.

The students will answer the questions associated with the activity