[ Secondary Science Instruction ]


What's in the Water?

Activities Using Computer Based Labs with Probes to Acquire Data




[ Temperature | pH | Dissolved Oxygen | Turbidity | Nitrates and Phosphates ]

Part C: Dissolved Oxygen

Overview/Introduction:

Aquatic animals need dissolved oxygen to survive. Oxygen gets into the water through diffusion between the air and the surface of the water, wave action, and plant growth. The amount of dissolved oxygen is dependent on temperature, barometric pressure, human activity, and decomposition.

Purpose or Objective:

  1. To accurately determine the amount of dissolved oxygen in the water.

Materials, Tools, and Resources Needed: Chart of 100% dissolved oxygen capacity (mg/L) for temperature and barometric pressure, CBL, Graphing calculator or lap top, Dissolved oxygen sensor, 250 ml beakers, distilled water, 100% calibration bottle, Sodium sulfite calibration solution, DO electrode filling solution

Time Required: one period

Teacher Preparation:

It is important to take a sample as far away from the shore as possible. Do not sample surface water. See Preparation-Collecting Samples for instructions on how to make a water sampler.

Be sure to prevent mixing of your water sample with air. Taking measurements at the field site is more accurate. If you must postpone measurement until you return to the classroom, store your sample in an ice chest.

Procedure for CBL (see CBL manual for complete instructions):

  1. Prepare the dissolved oxygen probe. Connect the dissolved oxygen sensor into the CBL interface. Use the link cable to connect the graphing calculator or lap top to the interface.

  2. Place the probe in water.

  3. Turn on the calculator or lap top and start the data program.

  4. With the probe in water, wait 10 minutes until the probe warms. Select SETUP.

  5. Calibrate the dissolved oxygen probe. BE SURE no air bubbles are trapped below the tip of the probe.

  6. Set up the data collection mode

  7. Rinse the probe tip with a sample of water. Place the tip in the stream or water sample to a depth of 4-6 cm. Gently continuously stir your water with your probe.

  8. When the readings stabilize, select START to begin sampling. Continue stirring.

  9. The dissolved oxygen value will appear on the screen after 10 seconds.

    Repeat steps for additional sites and samples.

Student Handouts/ Record Sheets

  1. Data chart

Student Discussion Questions:

  1. Predict what would happen to the amount of dissolved oxygen at night. What will happen beginning at dawn and at noon.

  2. Algal bloom may occur in fresh water bodies when there is a sudden rise in temperature and nitrates. How will this large population of algae affect the amount of dissolved oxygen in the water? What happens when the algae population begins to die? How does this affect the amount of dissolved oxygen. What may happen to fish and other aquatic organisms?



Grade 9-12

California Science Content Standards

Acids and Bases

5. Acids, bases, and salts are three classes of compounds that form ions in water solutions. As a basis for understanding this concept:

  •  
    		• Students know the observable properties of acids, bases, and salt solutions.

  •  
    		• Students know acids are hydrogen-ion-donating and bases are hydrogen-ion-accepting substances.

  •  
    		• Students know how to use the pH scale to characterize acid and base solutions.

    Solutions

    6. Solutions are homogenous mixtures of two or more substances. As a basis for understanding this concept

  •  
    		• Students know the definitions of solute and solvent.

  •  
    		• Students know how to calculate the concentration of a solute in terms of grams per liter, molarity, parts per million, and percent compositions

    Ecology

    6. Stability in an ecosystem is a balance between competing effects. As a basis for understanding this concept:

  •  
    		• Students know how to analyze changes in an ecosystem resulting from changes in climate, human activity, introduction of nonnative species, or changes in population size.

  •  
    		• Students know how water, carbon, and nitrogen cycle between abiotic resources and organic matter in the ecoystem and how oxygen cycles through photosynthesis and respiration.

    Investigation and Experimentation

    Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and to address the content in the other four strands, students should develop their own questions and perform investigations. Students will:

    a. select and use appropriate tools and technology (such as computer-linked probes, spreadsheets, and graphing calculators) to perform tests, collect data, analyze relationships, and display data.

    National Education Technology Standards for All Students

    3. Technology productivity tools

    Students use technology tools to enhance learning, increase productivity, and promote creativity.

    Technology research tools

  •  
    		• Students use technology to locate, evaluate, and collect information from a variety of sources.

  •  
    		• Students use technology tools to process data and report results.

  •  
    		• Students evaluate and select new information resources and technological innovations based on the appropriateness to specific tasks.

    Technology problem-solving and decision-making tools

  •  
    		• Students use technology resources for solving problems and making informed decisions.

  •  
    		• Students employ technology in the development of strategies for solving problems in the real world.

     

     

     

     

     


    The Integrating Technology into Science Instruction webpages project is partially funded by grants from The Boeing Company and The Ralph M. Parsons Foundation. Integrating Technology into Instruction is a project of Target Science (target@laep.org) and is displayed on the Los Angeles Educational Partnership Learning Exchange. Target Science is an initiative of the Los Angeles Educational Partnership.
    Updated August 2000