Dissolved oxygen and the temperature of waterScience project video

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Complexity level:
5
Project cost ($):
Time required:
Does not include time required to obtain a water quality kit, which may be purchased online or at an aquarium shop.
Material availability:
Safety concerns:

This science fair project involves an electric aquarium heater and water as well as chemicals contained in the water quality kit. Appropriate care should be taken to avoid injuries.

Abstract

While most of us do not give much thought to water quality, serious aquarists are keenly aware of the importance of maintaining water quality. But while aquarists are careful to maintain ph, nitrates, and ammonia levels, many do not give the same attention to the level of dissolved oxygen (DO). An understanding of the relationship between temperature and DO is the subject of this science project. With the understanding gained from this experiment, you will have insight on how tropical and cold water fish are able to survive in their respective environments.

Objective

Determine the relationship between temperature of water, and dissolved oxygen.

Background

Sub-atomic particles are more active at higher temperatures, resulting in oxygen atoms breaking their molecular bonds. Water is composed of one hydrogen atom and two oxygen atoms. Once the atomic bond is broken, the oxygen atoms break free, resulting in there being less oxygen in the water. At cooler temperatures, there is less activity at the atomic level; hence, oxygen is retained in the water. At the other extreme, all oxygen is lost when water is boiled. Some warm water fish species have adapted to lower levels of oxygen in water, by obtaining additional oxygen from the atmosphere.

Scientific Terms

Dissolved oxygen

Materials

  • Three large jars
  • Aquarium heater
  • Water quality kit
  • Refrigerator
  • Paper
  • Pen or pencil
  • Thermometer

Procedure

  1. Prepare three large jars or beakers of with water and label the jars A, B, and C. Check the DO level using the water quality kit.
  2. Record the DO level for each jar on a piece of paper.
  3. Set jar A in a safe place and let it sit for five days at room temperature.
  4. For jar B: Place the aquarium heater and set for 80 degrees Fahrenheit (27 Celcius.). Maintain the temperature for five days.
  5. For jar C: Place the jar in the refrigerator for five days. The temperature within the refrigerator should typically be at 35-38 degrees Fahrenheit (2-3 degrees Celcius.)
  6. At the end of five days, check the DO level for all three jars.
  7. What changes can you observe in the DO of each of the three jars?

Discussion

Marine life in the extreme depths of the ocean is less abundant than waters closer to the surface. Yet, dissolved oxygen is more abundant in cooler waters, which is characteristic of deep sea waters. You would therefore typically expect to find a greater concentration of marine life in what should be oxygen-rich deep sea waters. How would you explain this apparent contradiction?

Questions & Answers

What is dissolved oxygen?

The amount of oxygen dissolved in water. Under average conditions, the concentration of oxygen in water is at less than one percent.

Make it Your Own

Conduct an experiment to find when water contains a peak concentration of oxygen.

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