Grade 5-8 Performance Task
Contributed by: New York State Education Department (NYSED)
NYS Alternative Assessment in Science Project (1996)

Student #2

Task:

At this station you will be observing a model of chemical weathering processes.

Materials:

• 3 clear plastic cups (with 100 mL line marked)
• hot water (45-50 degrees Celsius)
• room temperature water
• paper towels
• 1 thermometer
• 4 effervescent antacid tablets
• ice water
• waste container
• 2 Styrofoam or insulated cups (for transfer of hot liquid)

Background:

What effect does water temperature have on the rate of a chemical reaction similar to the interaction of a weak acid and carbonate rock, such as limestone or marble? To examine this question, you will observe a model that simulates the interaction of water and limestone. The "limestone" in your model will be an effervescent antacid tablet. This tablet will dissolve in water much more quickly than the limestone in nature, making it possible for you to collect data during this task.

Directions:

1. Put 100 mL room temperature water into the marked, clear cup and record its temperature on the data table.
2. Set your timer to zero or watch the wall clock. Place one tablet into the cup of water. Measure the time it takes for the tablet to dissolve completely and record this time on the data table on the next page.
3. Using only the materials listed above, design a controlled experiment to determine the effect of temperature on the rate of chemical weathering.
4. In the space below, write out the steps you will follow in performing a controlled experiment. Be specific enough so that another student could follow your directions and successfully complete the experiment.

5. PERFORM YOUR EXPERIMENT. However, do not use water with a temperature above 50 degrees Celsius.

6. Summarize all your data on the data table below.

7. Use the data from the table to construct a graph. Graph your data using temperature and time as your variables. Label both axes.

8. If this experiment was repeated with the antacid tablets ground into a fine powder, draw a dashed line on the graph that you think would show the result. In the space below, use complete sentences to explain why you placed the line where you did.

9. If this activity was an accurate model of the actual chemical weathering of rock material on the Earth, how would climate temperatures affect the rate of chemical weathering of rock surfaces? Answer in a complete sentence.

10. Describe how you would design an experiment to explore the effects that variations in the strength of weak acid solutions would have on the rate of chemical weathering? Include at least 4 variables that you would consider.

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