Take samples from the tops and bottoms of each jar. Be careful not to introduce oxygen by mixing while taking samples. Record and compare. Identify whether there is a maximum or saturation level of dissolved oxygen. Time Needed 2 class periods.
Place covers on both jugs and shake jugs until the salt solution is mixed.
Be sure both are shaken equally hard and long. Fill one jar with salt water and the other with fresh water. Let them sit ten minutes while you fix the other jars. Mark the reading on the jar. Place them in the refrigerator.