Technology Idea
Cranberry Juice
Neutralization
Probeware Lab

Background:

If you eat or drink something that is too acidic, or if you over-eat, it may upset your stomach. Many antacid products reduce the acidity of the stomach contents that can to provide relief.

Acidity is measured using the pH scale. The lower the value of the pH reading, the more acidic the solution. For example, cranberry juice has a pH of about 3.5, while distilled water, which is considered neutral, has a pH of 7.

By adding an antacid to an acid, the pH is raised. In this lab, you will compare various antacid products and their ability to raise the pH of an acidic liquid (cranberry juice).

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The Questions:

What occurs when a base is added to an acid? Which antacid is most effective?

Variables:

Identify the type of data you will collect to support your hypothesis and state the manipulated, responding and controlled variables in this investigation.

SAFETY REMINDER: Wear protective equipment while handling chemicals.

Materials:

  • pH sensor and link to computer
  • 500 ml beaker
  • cranberry juice
  • selection of antacid products (Alka-Seltzer, Tums, Rolaids, Mylanta, etc.)

    Procedure:

    For this activity, a pH sensor is used to track the pH change of cranberry juice over time.

    In your science notebook, write down your prediction about what will happen when you add the various antacids to the cranberry juice. Which one do you think will be most effective in reducing the acidity of the cranberry juice?

    Step 1:

    Connect the pH sensor to your computer - if you are using a USB connection your apparatus will look something like this:

    Step 2:

    Configure the data collection software to collect pH data over time.

    The following is an example DataStudio graph setup:

    Step 3:

    Pour approximately 150 ml of cranberry juice into the beaker. Place the pH sensor into the beaker of juice. Start recording data.

    Step 4:

    Read the antacid package carefully to determine the manufacturer's recommended dose for the product. Add this amount of the product to the cranberry juice. Very gently swirl the pH sensor (do not bang it against the walls of the beaker) so that the antacid product mixes thoroughly with the juice. Continue to collect data until the antacid is completely dissolved and the pH reading has stabilized. Stop recording data

    Step 5:

    When you have finished collecting your pH data, you are ready to analyze it. Re-scale the graph so the data fills the whole window. If possible, print out the resulting graph.

    Find the lowest pH you recorded. (If you are using DataStudio software, click on the “Smart Cursor” button . The cursor becomes a crosshair which you can drag over the graph in order to more easily determine the coordinates at any particular point.) Write down this pH in your notes, or on the graph print out.

    Find the highest pH you recorded. Write down this pH in your notes, or on the graph print out.

    Now note the time on the graph that the pH started to change, and also the first time on the graph that the stabilized pH reading (after the addition of antacid) was reached. Subtract these two times to find the overall time of pH change.

    Carefully dispose of the beaker contents as instructed by your teacher.

    Step 6:

    Repeat steps 3 to 5 for each of the antacid products.

    Forming Conclusions:

    Based on the data you have collected, write a summary statement for the following questions:

    1. What occurs when a base is added to an acid?
    2. Which antacid was the best at reducing pH? Explain.
    3. Was there a difference in the time that it took raise the pH? Explain why. What might this mean for someone who is suffering from stomach upset?
    4. Was the comparison of antacid products in this experiment completely fair?

    Extending:

    • Discuss with your classmates how you might repeat this experiment to make the results more reliable, or the comparison between antacid products more fair. If you think improvements could be made, make changes to the procedure, and repeat the experiment.

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