Unit 8 Phenomenon Demo
Directions: Follow the steps for the demonstration below. When done, complete the corresponding
phenomenon worksheet.
● Materials: 1 glass beaker, 1 straw, 50 ml of water in cup, 25 drops of pH indicator, timer(phone works)
● Procedure:
1. Fill the beaker with 50 ml of tap water.
2. Use the eyedropper to add 25 drops of pH indicator to the water.
Record the initial color of the water (with the drops) in the table below. Use the scale below to help you
determine the initial pH number.
Initial Color (with drops)
pH scale number
3. Insert the straw into the cup, it should touch the bottom of the cup.
4. Set a timer for 1 minute.
5. Start the timer and slowly blow into the straw. DO NOT suck into the straw! Pause momentarily to catch
your breath if needed.
6. After 1 minute, observe the color of the water carefully. Record your observations below.
Final Color
pH scale number
pH Scale
Part 2: Chalk & Acid (Class Demonstration)
We are now going to investigate how carbonic acid affects organisms with shells (like plankton). Shells are made with
calcium carbonate. As oceans become more acidic, less calcium carbonate is available for these organisms. Chalk also
contains calcium carbonate.
Hypothesis: Of the 3 solutions (tap water, ammonia water, and vinegar water) which one will affect the chalk most?
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Record the following data:
Tap Water
Ammonia Water
Vinegar Water
Initial pH
Chalk Observations:
Tap Water
Initial Observation
After 1 minute
Ammonia Water
Vinegar Water
After 7 minutes
Analysis Questions (answer using complete sentences):
1. What happened to the chalk in each of the solutions?
2. Was your hypothesis supported? Explain why or why not.
3. Which solution affected the chalk most and why?
4. Why did bubbles appear? What was in the bubbles?
5. Recall that chalk and shells are both made of calcium carbonate. What can you conclude about the effects of
acidic solutions on calcium carbonate? How might this affect marine organisms that create shells? How might this
affect the oceanic food chain?