Also, monitor the pH of the solutions as the tests are per-formed. I found that the pH drifted considerably while students were working. I assumed this was due to students contaminating samples by transferring liquid between samples on the tweezers used to hold the pH paper. Remember to first describe what you actually see, then interpret or give it meaning based on what you ve learned. Students need to be able to use the terms pH, acid, base, and alkaline appropriately and be able to describe cause-effect relationships with some justification, using data and prior knowledge.
Students describe, predict, investigate, analyze, and explain phenomena.
Students look for evidence that explains why things happen, and modify explanations when new observations and data are obtained. Students use computers to organize, analyze, and interpret data. Resource demands can limit the growth of populations in specific ecosystems. I prepared a station with eight or nine beakers of pond water for every five or six students. I labeled the beakers with dates from about 1965 through 1996 - so as to mimic samples being taken every four years or so.