Fill out document that is attached with this question. Note: It is suggested that you perform this experiment with a minimum of one and a maximum of seven assistants who are able to follow the exact directions you will give them. If no assistants are available, the lab may be performed alone.
- Read each of the following steps before beginning.
- Locate the 8 clear plastic 9 oz. cups provided in your kit and place the cups in a line.
- Pour the entire 30-mL bottle of sodium hydroxide (NaOH) into the first cup. The NaOH will act as the disease-causing microorganism.
- Use the tablespoon-size measuring spoon to add exactly 2 tablespoons of distilled water to each of the remaining 7 cups.
- Warn your assistant(s) that any of the cups may contain a strong base, NaOH. They must be very careful in handling all solutions.
- Have an assistant rearrange the cups without anyone else watching. Rearrange the cups yourself so that no one knows which cup holds the pathogen.
- Form a hypothesis about the number of cups that will contain the disease-causing microorganism at the end of this experiment. Record the hypothesis in Data Table 3.
- Make the following announcement to the assistant(s):
- The following activity will simulate the spread of a disease-causing microorganism at a luncheon. One individual at the luncheon has contracted the disease within the previous 24 hours. However, this individual is unaware of the disease because they have not begun to exhibit symptoms. During the luncheon, many individuals are sharing and tasting the beverages and food. To simulate sharing of beverages at the luncheon, you will mix the beverage I am about to hand you with 3 different people. To mix beverages, carefully pour all of the contents of your cup into another persons cup. The person with the full cup will then pour ½of their cups contents back into your cup. Share drinks with a total of 3 people. It is very important that no one actually drinks any of the beverages.
Note: If you have only 1 assistant or are performing the exercise alone, this activity can be simulated by randomly mixing each beverage 1 time with 3 other cups, until each cup has been switched.
- Have the assistant(s) begin the exercise, mixing the solutions.
- When all solutions have been mixed, use scissors to snip off the tip of the phenolphthalein pipet.
- Carefully dispense 3 drops of phenolphthalein into each cup.
- Phenolphthalein will act as a test for the disease; pink indicates a positive test result. Identify which solutions test positive for the disease.
Note: Phenolphthalein is an acid-base indicator which will change from colorless to pink at a pH between 8.2 10.0. In other words, phenolphthalein will turn pink in the presence of bases, such as NaOH.
- Complete Data Table 3, answering each of the following:
- The number of beverages at the luncheon.
- The number of people who arrived at the luncheon with a contagious disease.
- The percent of people who began the luncheon with the infectious disease; this is the number of people who began the exercise with a contagious disease divided by the number of beverages.
- The number of people who contracted the contagious disease by the end of the luncheon.
- The percent of people who contracted the contagious disease; this is the number of people who ended the exercise with a contagious disease divided by the number of beverages.
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