Name______Period______Redo______

Chalk It Up to Weathering Lab #25

Chalk is a type of limestone made of the shells of tiny organisms. When you write your name on the chalkboard or draw a picture on the driveway with a piece of chalk you are leaving behind dead organisms. By scraping the chalk against the ground you are mechanically (physically) weathering the chalk. This experiment will help you understand how chalk can be chemically weathered.

Problem: What variables affect the rate of chemical weathering?

Hypothesis: How do you think acidity, surface area, and temperature affect the rate (speed) of weathering of chalk? Answer each questions below, remember to include a reason for your guess.

Acidity: What happens to chalk in water or acid (vinegar)? ______

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Surface area: How will the size of the chalk pieces affect the rate of weathering?

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Heat: What will happen if you heat the acid?

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Materials:

·  2 150 ml beakers

·  6 small pieces of chalk

·  Vinegar

·  Water

·  Hot water heater

Procedure:

Safety: Goggles or must be worn at all times while working on lab

Test A: Acidity

1.  Measure 60 ml of water.

2.  Place 1 piece of chalk into the beaker with the 60ml of water.

3.  In a separate beaker, measure 60 ml of vinegar.

4.  Place 1 piece of chalk into the beaker with the 60ml of vinegar.

5.  Record detailed observations for each beaker every minute for 5 minutes. (5 observations per test)

6.  Empty the beakers in the sink and throw the chalk away.

Test B: Surface Area

1.  Measure 60 ml of vinegar.

2.  Crush 1 piece of chalk.

3.  Place the crushed pieces of chalk into the beaker with the 60ml of vinegar.

4.  In a separate beaker, measure 60 ml of vinegar.

5.  Place 1 piece of chalk into the beaker.

6.  Record detailed observations for each beaker every minute for 5 minutes. (5 observations per test)

7.  Empty the beakers in the sink and throw the chalk away.

Test C: Heat

1.  Measure 60 ml of cold vinegar.

2.  Place 1 piece of chalk into the beaker with the 60ml of vinegar.

3.  In a separate beaker, measure 60 ml of warm vinegar.

4.  Place 1 piece of chalk into the beaker with the 60ml of warm vinegar.

5.  Record detailed observations for each beaker every minute for 5 minutes. (5 observations per test)

6.  Empty the beakers and throw the chalk away.

Data Table:

Table 1: Affects of acidity

Acidity observations (describe, draw, and summarize)

60 ml of water
60 ml of vinegar

Table 2: Affects of Surface Area

Surface Area observations (describe, draw, and summarize)

60 ml of vinegar
(crushed chalk)
60 ml of vinegar
(whole chalk)

Table 3: Affects of temperature

60 ml of room cold vinegar
60 ml of warm vinegar

Analysis and Conclusion

1.  Did the chalk look any different after being in the vinegar?

2.  What were some signs that chemical weathering was occurring?

3.  Which substance, water or acid (vinegar) weathered the substance more quickly? Why?

4.  Was your hypothesis supported by the data? Explain why your hypothesis was either correct or incorrect?

a.  Acidity:

b.  Surface area:

c.  Heat:

5.  Does the amount of surface area make a difference in the rate of chemical weathering? Explain your answer.

6.  How does heat affect the rate of chemical weathering?

7.  What does this lab imply about weathering in the tropics compared to the poles?

8.  What type of chemical weathering was tested in this experiment?

9.  What is the other agent of chemical weathering?