Lake Models Worksheet – Part 1

Name(s)_____________________________________________

Date___________________________________

Water is essential to life on earth and totally dominates the chemical composition of all organisms. The characteristics of water regulate a lake's metabolism. Its unique thermal-density properties, specific heat, and freezing point allow the formation of a stratified environment which controls the chemical and biological properties of lakes. In Part 1 of this lesson you create summer and winter lake models.

Knowledge Base
See the student reading on the Unique Properties of Water.

Experimental Design
You need to create summer and winter lake models based on temperature density stratification. The following materials are necessary.

1. two 5-10 gallon aquaria
2. plastic ruler
3. thermometer
4. red food coloring
5. 2 gallon carboy with valve/tygon tube/U-tube assembly
6. salt
7. Pasteur pipettes
8. 5 gallons of refrigerated tap water (4-5°C)
9. Winter Lake Model

Fill one aquarium 2/3 full with pre-chilled water and add crushed ice to surface. Complete your Data Collection, Data Management and Analysis for the winter lake model, and Interpretation of Results question 1 before beginning the summer lake model.

Summer Lake Model

Fill the aquarium 2/3 full with pre-chilled water. Using the carboy, tape the U-tube to a side wall so that the opening is just below the surface. Slowly add a layer of warm tap water which has been colored with red food coloring.

Data Collection
Winter Lake Model

Record temperature at 2 cm intervals.

Summer Lake Model

Record temperature at 2 cm intervals.

Data Management and Analysis
Create graphs of the temperature data. Remember to label axes and legends and title your graph.

Fill a jar with hot water (from faucet) and add enough food coloring to make it very red. Forcefully inject it as deep as possible into the winter lake model and observe how the water behaves. After you have recorded your observations for the winter lake model, fill another jar with hot water and add food coloring to make it very red. Forcefully inject it as deep as possible into the summer lake model and observe how the water behaves.

Interpretation of Results
1. How does the water in the winter lake model respond after the hot water is injected? Why?

2. How does the water in the summer lake model respond after the hot water is injected? Why?

Make up several jars of different temperature water (ice water, 10-15°C, hot, and hot plus a tablespoon of salt), and inject each at different depths and observe the behavior of the water.

Reporting Results
Be prepared to share your results with the class and to explain any discrepancies in results. Turn your worksheet in to your teacher.

Temperature Density Stratification in WOW Lake Worksheet – Part 2

Name(s) __________________________________________________________

Date ______________________________

Knowledge Base
Consider what you have learned about the properties of water from the student reading and the lake models laboratory exercise. What WOW data might replicate your lab models?

Experimental Design
You need to use WOW temperature data and the Profile Plotter to determine if the results from your lab lake models apply in an actual lake environment.

1. What data might verify your results?

Data Collection
Collect temperature data for Ice Lake on January 2, 1999 and July 2, 1999.

Data Management and Analysis
Create a graph of the temperature profiles for Ice Lake. Remember to label your axes and legends and title your graphs.

Interpretation of Results
2. Using the Ice Lake Profile Plotter when does the lake become isothermic?

3. What environmental conditions contributed to making the lake isothermic?

4. Does your analysis verify your lab results? If not, what additional data are required?

Reporting Results
Be prepared to present your results to the class. Be prepared to explain any discrepancies in the data. Turn your worksheet in to your teacher.