Effects of Chemical and Thermal Pollution
Student Laboratory Kit
Materials Included In Kit
Bromthymol blue solution, 0.04%, 100 mL
Dextrose, C6H12O6, 70 g
Iron(III) sulfate, Fe2(SO4)3, 50 g
Yeast, 42 g
Containers, with holes in lids, 120-mL, 20
Pipets, graduated, disposable, 5
Tubes, sample, 20
Tubing, plastic, 12", 20 pieces
Additional Materials Required
Water, distilled, 380 mL†
Water, distilled, 500 mL*
Sodium hydroxide solution, 0.1 M (optional)†
Balance, 0.1-g precision*
Beakers, borosilicate, 150-mL, 2*
Hot plate or other heat source*
Test tube rack*
*for each lab group
†for Prelab Preparation
- Prepare a 0.002% solution of bromthymol blue by mixing 20 mL of the supplied 0.04% bromthymol blue solution and 380 mL of distilled water.
- Make sure this solution is blue. If it is not, add dilute sodium hydroxide (0.1 M) dropwise until it is blue.
- Prepare enough (1 L) 80 °C and 45 °C DI water for five student groups. Also have 500 mL of room temperature DI water on hand for student use.
Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Wear heat-resistant gloves when handling the beakers with the heated water. Wash hands thoroughly with soap and water before leaving the laboratory. Follow all laboratory safety guidelines. Please review current Safety Data Sheets for additional safety, handling and disposal information.
Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding.The resulting solutions may be disposed of according to Flinn Suggested Disposal Method #26b.
- Enough materials are provided in this kit for 5 groups of students. This laboratory activity can reasonably be completed in one 50-minute class period.
- As an extention, calcium sulfate may be used to show that it will not inhibit gas production or prevent a color change in the indicator. Iron(III) sulfate will inhibit the CO2 gas production and the indicator in the sample tube should remain blue.
- One hot plate station may be used if desired so that the heated distilled water solutions required for every student group may be dispensed at the same time.
- This is a great activity to perform during discussions about respiration, fermentation and environmental conditions.
- If enough hot plates are not available, an option for hot water is to use a large hot pot or coffee perculator. A laboratory microwave is another option. Be sure to use beaker tongs or wear heat-resistant gloves.
- If sucrose is used instead of dextrose, it will take longer to begin producing CO2, but the rate will eventually be the same as the flasks containing dextrose. Yeast cells are able to begin respiration more quickly using a monosaccharide (e.g., dextrose) than a disaccharide (e.g., sucrose) as a food source. This is due to the inability of yeast to metabolize disaccharides. In order for yeast to use sucrose as an energy source, the yeast must first break it down into its component disaccharides of glucose and fructose—these are called invert sugars. This extra step, which delays the start of fermentation, is carried out by the enzyme invertase.
- Ammonium oxalate, calcium chloride and iron(III) sulfate will all affect the production of gas and a color change in the indicator, with iron(III) sulfate preventing these occurrences altogether. Iron, halide ions and cyanide ions also have the greatest ability to inhibit or prevent yeast metabolism. Even NaCl in high enough concentration will prevent metabolism in yeasts.
- The following is a list of common ions (and their sources) found in water sources:
Carbonate: Comes from the high water solubility of carbonate material and rocks, such as limestone and dolomite. Another source of carbonate ions is from dissolved atmospheric carbon dioxide. When heated in the presence of calcium and magnesium, alkaline water containing carbonates will form crust-like scales in pipes restricting the flow of fluids and also causing the release of carbon dioxide gas.
Chloride: Dissolved from rocks and soils and present in sewage and industrial wastes. When chloride is in excess of 100 parts per million, water has a salty taste and when it is in excess of 150 parts per million, physiological damage may occur. Chloride also increases the corrosiveness of water when it is present in higher concentrations.
Chromate: Comes from industrial waste and is used to prevent corrosion in cooling towers. When chromate accumulates in large amounts in the human body it may cause cancer.
Iron: Present in natural sources, such as rocks and soils. Iron is also found in industrial waste and is present from the corrosion of iron pipes. When the concentration of iron is above 100 parts per billion, it will precipitate when it comes in contact with air. This will in turn stain laundry, plumbing fixtures, and silverware. It will also cause food and drinks to taste and look peculiar.
Lead: Found in water from plumbing, coal, and gasoline sources. A major source of lead pollution came from lead additives in gasoline prior to the 1980s (the structure of the gas has since been changed to cut down on the pollution risk). The EPA estimates that 20% of our exposure to lead comes from drinking water. At blood levels greater than 100 parts per billion, anemia, kidney damage and mental retardation can result.
Phosphate: Comes from fertilizers, detergents, wastewater of domestic origin such as human, animal and plant residue, and from wastewaters of industrial origin. Phosphate is added to farm and city water systems to control hardness. Phosphates from laundry detergents can result in overgrowth of algae, which in turn will cause the algae to die at a high rate and undergo decomposition. This decomposition process depletes oxygen from the water and will result in increased fish kill.
Sulfate: Dissolved from rocks and soils that contain sulfides and gypsum. Sulfate is also due to industrial waste in liquid or gaseous forms. When sulfate is present with calcium, scale will result in pipes and steam boilers. Sulfate concentrations of 500 parts per million produce water that tastes bitter and sulfate concentrations of 1,000 parts per million may be cathartic.
Correlation to Next Generation Science Standards (NGSS)†
Science & Engineering Practices
Developing and using models
Planning and carrying out investigations
Analyzing and interpreting data
Constructing explanations and designing solutions
Disciplinary Core Ideas
MS-ESS3.C: Human Impacts on Earth Systems
HS-ESS3.C: Human Impacts on Earth Systems
Systems and system models
Stability and change
Temperature and Yeast
Answers to Questions
- How did the temperature of the solutions affect the yeast cultures? The yeast culture at 45 °C produced the most CO2 and was the most viable.
The yeast culture at room temperature eventually produced CO2 but at a much slower rate than the 45 °C solution. The yeast culture at 80 °C did not produce any CO2.
- Given the results, describe the relationship among the 80 °C, 45 °C and room temperature solutions. Include the relationship between dissolved oxygen and CO2 production of the yeast.
Initially, as the temperature increased the rate at which the yeast consumed oxygen increased. The increased temperature decreased the ability of the oxygen to dissolve in water. This means that the yeast used up the available oxygen more quickly at the higher temperatures. If the temperature was too hot (80 °C), the yeast cells were not viable.
- How did the iron(III) sulfate effect the yeast growth and CO2 production?
The iron(III) sulfate eliminated the CO2 production and viability of the yeast culture.
- What happened when the containers were swirled at each five-minute mark? Why?
For the containers that produced CO2, the amount of gas travelling from the container to the sample tube increased. More oxygen was introduced to the containers as they were swirled.
- A dam has just been installed in a local river. How would the dissolved oxygen readings above and below the dam vary?
The water below the dam should be oxygen rich due to the increased motion of the water. The water above the dam should be more stagnant and therefore would be more likely to have less oxygen than the water below.
- A nuclear power plant with a cooling lake is being installed in your area. The water from the cooling lake is eventually going to be introduced to a local natural water source. What effect would the water from the cooling lake have on aquatic organisms if the water from the power plant was introduced to the natural water source before it completely cooled?
Answers will vary. It is really dependent on the temperature and amount of the cooling lake water entering the natural source and the overall size of the water source.
- Describe two ways pollution could be reduced or prevented in natural water sources in your area.
Student answers will vary.
||Water, Distilled, 4 L
||Flinn Scientific Electronic Balance, 1000 x 0.1-g
||Beakers, Borosilicate Glass, 150-mL
||Hot Plate, Temperature Controlled
||Test Tube Rack, Wood, 6-Tube, 25 mm Hole Size
||Filtering Funnel, Polymethylpentene, 70 mm, Stem Length 150 mm