Table of Contents Module 5


Part II: Water Testing Outdoors - 40 minutes


Collect a Sample 1. Have a few students work together to collect a surface water sample by the docks or beach. Put students in groups of 2 and have them each take a small sample. This water will be used to test for temperature, salinity, specific gravity, and pH.


2.


Note: A Van Doran bottle can be used to collect water samples from different depths. See resources for information on how to make your own.


Temperature 3. Using a thermometer, have students compare the temperature of the air to the surface water temperature. Ask which is warmer and why, then explain the differences between air and water temperature. Explain that air temperature and water temperature are different. They require two separate readings. Ask students why they think air and water temperature are different?


4. Instruct students to record their data in the water quality chart. This test can be repeated with multiple samples of surface water to obtain a more accurate temperature.


Salinity 5. Have students carefully submerge a hydrometer straight down in the previously obtained bucket of surface water. They should then record the salinity or specific gravity at the point where the surface of the water touches the stem of the hydrometer needle. Ask students to compare the ppt of their sample with deep ocean water (35ppt).


Specific Gravity 6. Using the hydrometer, have students observe and record the specific gravity, or density, of the surface water. Ask them to compare their results with the Specific Gravity of fresh water (1 SG).


7. In between samples, advise students to rinse the hydrometer with fresh water in order to obtain the most accurate results.


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