Objective of the research

To find out whether the big goldfish or the little goldfish will produce more CO₂ if contained in the same amount of water.

Hypothesis

The big fish will produces more CO₂ because it has a larger body mass.

Introduction

All living organisms on the Earth require energy to maintain various processes connected with their lives. “Cellular respiration is the process by which the chemical energy of “food” molecules is released and partially captured” (Pearson Education 2010). Aerobic organisms have oxygen-based metabolism, which means that when exposed to aerobic respiration they will use O₂ (oxygen) and produce CO₂ (carbon dioxide).

Heterotrophs

Heterotrophs are single or multi-celled organisms that cannot capture the energy of the sun directly through the process of photosynthesis. As a result heterotrophs are considered to be consumers in the food chain. In the following experiment this specific fact has an important meaning. Goldfish is an aerobic heterotroph, which cannot produce O₂.When put into the water or any other substance, goldfish will use O₂ instead to stay alive. As a result the amount of O₂ in the water will decrease and the amount of CO₂ will increase depending on the time the fish is in the water.

Cellular Respiration

Cellular respiration is a combination of metabolic reactions that take place in every cell of the organism, which converts biochemical energy (energy contained in food) into the energy currency of the living organism – Adenosine Triphosphate (ATP) and waste products.

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (36 or 38 ATP molecules)

The formula shown above is another milestone of the following experiment. A molecule of glucose combined with oxygen results in release of carbon dioxide, water, and energy. The arrow in this reaction is a substitute for various complicated reactions that occur at the cellular level.

Phenolphalein

Phenolphalein (C20H14O4) is the chemical compound that changes its color in strongly acidic and basic environment. As a result of cellular respiration some amount of CO₂ will be released into water.

CO₂ + H₂O → H₂CO₃ (carbonic acid)

When carbonic acid is neutralized by NaOH (caustic soda), phenolphalein will remain colorless, since the environment will be neutral or nearly neutral.

H₂CO₃ + 2 NaOH → Na₂CO₃ + 2 H₂O

However, if the amount of H₂CO₃ is less than the amount of NaOH, then by adding some amount of phenolphalein researcher may obtain basic environment in the water. In this case the water will change its color to pink.