Christina Pominville

Name _________________________________________Date__________________

Rate of Weathering Lab                                                            period ______________

Rate of Weathering Lab

Purpose:  This lab explores how various factors effect the rate at which chalk will dissolve (weather).

Introduction: Everyday, rocks on the surface of the Earth are subjected to weathering by physical and mechanical elements like wind, acid rain, or ice. Calcium Carbonate, the substance that makes up calcite and limestone (not to mention antacids for when you have an upset stomach) reacts with any type of acid (like hydrochloric acid- HCl) upon contact. This reaction is:

CaCO₃ + 2HCl => H₂O + CaCl₂ + CO₂

In this reaction, the acid combines with the calcium carbonate to make water, calcium chloride, and carbon dioxide.

After the demonstration of this reaction, what do you think the bubbles are made of? (1)

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What do you think will speed up this reaction the most? (1)

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What do you think will slow down this reaction? (1)

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The time for the control experiment, with 2 pipettes of 2M HCL and 1/8^th a piece of chalk is: _________________________. (1)

Your group is going to change a variable and determine if the reaction will go faster or slower. Write your hypothesis here. (12) ________________________________________________________________________________________________________________________________________________________________________________________________________________________

Procedure:

* For your safety, use goggles and great care with the acid. It will burn your skin or eyes. If it spills, tell your teacher immediately.

1. Assign roles to each person in your group: (4)
   1. Facilitator: ____________________________
   2. Time keeper: __________________________
   3. Data collector: _________________________
   4. Secretary: _____________________________
2. Collect your materials. (4)
   1. Type of acid: _______________________
   2. Strength of acid: _____________________
   3. Amount of acid: _____________________
   4. Amount of chalk: ____________________
3. Make a data table to record your data in. Collect your data at 30 second intervals.
4. Perform your experiment carefully. 
5. When the chalk is completely dissolved, the reaction is complete. Make sure to record your end time : __________________________ (1)
6. Use excel to create a graph for your data. Label each axis with units.
7. Type your individual lab report.

Discussion Questions (10 each)

1. Define the term “weathering” in your own words.

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2. What is responsible for breaking down the chalk? _____________________________________________________________________

3. Is the reaction performed in this experiment an example of physical or chemical weathering? Why? _______________________________________________________________________________________________________________________________________________________________________________________________________________

4. Which rock do you think will weather faster: limestone in a hot climate or limestone in a cold climate? Why? __________________________________________________________________________________________________________________________________________

5. What would happen to the rate of weathering for the chalk if I smashed it before performing the experiment? Why? __________________________________________________________________________________________________________________________________________

Write your conclusion below, including all parts:

-         restate problem (5)

-         restate hypothesis (5)

-         how you did the experiment (5)

-         your results (5)

-         if you were correct or incorrect and why (5)

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