Effect of thermal stratification

Cyanobacteria blooms in Lake Kinnert can be explained by the effect of thermal stratification. The density of water depends on temperature: Surface waters are warmer and less dense compared to bottom waters that are colder and denser. These layers affect the vertical movement of oxygen and nutrients in water. This process is known as thermal stratification. Thermal stratification creates conditions which favor the growth of Cyanobacteria blooms (United states environmental protection agency, Office of Water EPA 820-S-13-001, 2013, Impacts of Climate Change on the Occurrence of Harmful Algal Blooms).

 Our question is: what is the correlation between thermal stratification of waters and the vertical movement of substances in stratified waters?

 To help us answer this question you are asked to perform an experiment demonstrating thermal stratification and movement of color between the water layers.

 For this you will need:

1.     Two identical clear, drinking glasses. 

2.     One teaspoon of freeze-dried coffee.

3.     Boiling water and cold water.

4.     A square of cardboard, large enough to cover your drinking glasses.

5.     Download to your Smartphone the application “Color Analysis”.


The following videos demonstrate the experiment:

1.      Apply white paper behind the glasses in order to examine the colors correctly.

2.      Completely fill in one glass with cold water.

3.     Completely fill in the other glass with boiling water, add one teaspoon of coffee, and mix well.

4.      Lay the square of cardboard carefully onto the top of the glass with the boiling water.

5.      Pick up this glass and turn it straight upside-down.

6.     Put it on top of the glass filled with the cold water.

7.     Carefully pull the card out.

8.     Take a picture of the lower part of the glass with the cold water using your Smartphone.

9.     Analyze the colors in the picture you just took using the “Color Analysis” application.

10.   Perform stages 1-8 again, only this time put the cold water on top of the boiling water mixed with the coffee.

11.  You should now have two values of blue color level of the dominant color found by the application:

#1 ___________ = blue color level of stratified water (hot water on top of cold water).

#2___________ = blue color level of non-stratified water (cold water on top of hot water).

Notice: Using the RGB (Red, Green, Blue) color model: Brown is made by combining red and green only, while White is made by combining red, green and blue colors!

Provide an answer by clicking on "Map" and then on "Add an Answer".

Results, Analysis and Discussion


History of edits
Edited BY: Shadi Asakle Edit Date: 2016-06-28 16:00:44
Created By: Anastasia Badiyan Edit Date: 2016-06-17 09:30:59
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