Properties of water density due to temperature and various concentrations of salt.

Items needed: Computer, Internet access, electronic scale, stirring rod, graduated cylinder, 5 – 100 ml beakers, food coloring (dye), table salt, 5 gallon subdivided glass tank, hot plates, ice & 1000 ml beaker for ice bath, access to tap water, thermometer.

Assignment / Instructions:

Students will be divided into 5 groups.

Each group will be assigned so many grams of salt, a color, and specific temperature of water for mixing in the 100 ml beakers. (Note: The water temperature should be approx. 50 degrees in the half filled fish tank.)

Each group will be creating a table to record the following data: Weight of the beaker. Weight of the beaker and water at the assigned temperature in degrees Fahrenheit before adding the salt. Weight of the beaker and water weight at assigned temperature in degrees Fahrenheit after adding the salt.

Group #1 – weigh out 5 grams of salt, assigned
yellow color & 90 degrees temperature.


Group #2 – weigh out 40 grams of salt, assigned
orange color & 50 degrees temperature.


Group #3 – weigh out 80 grams of salt, assigned

red color & 70 degrees temperature.


Group #4 – weigh out 140 grams of salt, assigned

blue color & 45 degrees temperature.


Group #5 – weigh out 220 grams of salt, assigned

green color & 35 degrees temperature.


Each group will mix the solution of color, water

& salt.


Once the each solution is prepared, the

instructor will add each group’s solution into

the tank while the student observe.


The students should observe the separation of

layers by color. This separation will simulate

how ocean currents behave due to the density

variations resulting from temperature & salt

concentration in water.

Graphing:

Have each students create three graphs using the recorded data. The students will use the computer to graphically illustrate the relationship of water density per salt
concentration, the second graph illustrating water density per change in temperature, and the third graph should show the relationship of water density per mixture of salt concentration
& water temperature.

Questions for the students to answer:

How does salinity in water change water density?


Which has a greater effect on water density temperature or salinity?


Based on the observations, where would you suspect the ocean water to have higher concentrations of salinity?


In those regions of the ocean that you would suspect higher concentrations of salinity, how will water temperature change the ocean currents… will there be an upwelling or downward flow pattern?

Internet Search and Conclusions:

Have each student search the topic “ocean currents” to find examples of what they observed in the classroom. For the conclusions, have the student write a one page summary incorporating the information they found on the web to provide examples these ocean currents found in different parts of the world and explain why these current may or may not be beneficial to people who live in these areas of the world.

Comments: Collectively, the class will be working together exchanging the data they have collected while doing the experiment.

Evaluation:

Points for completeness – 50%


Points for correctly answering questions – 20%


Points for graphs – 10%


Points for Internet search and conclusions – 20%

E-Mail

Matthew Stebbins

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