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Chemical Weathering in Geology Mark as Favorite (0 Favorites)

LAB in Observations, Chemical Change, Interdisciplinary, Physical Change, Reaction Rate, Reaction Rate, Chemical Change. Last updated January 10, 2019.

Summary

In this lab, students will explore the differences between erosion, weathering and chemical weathering. They will complete a lab experiment that simulates chemical weathering on 4 different types of rocks. They will also learn how to use the Mohs Hardness Test to analyze the results.

Grade Level

Middle school

Objectives

By the end of this lab, students should be able to:

  • Explain the difference between erosion, weathering and chemical weathering.
  • Carry out a test for mineral hardness.
  • Model the effects of chemical weathering.
  • Construct a scientific explanation based on evidence for how the uneven distributions of Earth’s mineral, energy, and groundwater resources are the result of past and current geoscience processes.

Chemistry Topics

This lab supports students’ understanding of

  • Chemical Reactions
  • Chemical Change
  • Observations

Time

Teacher Preparation: 15 minutes (more time needed depending on access to materials)

Lesson: 50 minutes

Materials

For one demonstration you will need:

  • package of 12 oz plastic cups
  • 1 liter of carbonated/seltzer water
  • 3 small pieces of limestone
  • 3 small pieces of granite
  • 3 small pieces of marble
  • 3 small pieces of sandstone
  • 1 penny
  • 1 iron nail
  • 1 piece of quartz
  • 1 permanent marker
  • Chromebooks/tablets for individuals or groups

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • Students should wash their hands thoroughly before leaving the lab.
  • When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.

Teacher Notes

  • Students may need to be given specific directions on how to carry out the Mohs Hardness Test for each rock. This paragraph describes what the Mohs Hardness Test is and how to carry it out:

During the early 1800s, a German mineralogist named Friedrich Mohs devised a scale that tested mineral hardness, which means the resistance of a mineral to being scratched. This scale, which ran from 1 to 10, was named after Mohs, and is known as the Mohs Hardness Test. For example a piece of Quartz would leave a scratch in a piece of Talc but the Talc would not be able to put a scratch in any of the minerals listed after it. The Mohs Scale is shown below, using commonly known minerals to represent each degree of hardness:

1
 Talc
 6 Feldspar
2 Gypsum 7 Quartz
3 Calcite 8 Topaz
4 Fluorite 9 Corundum
5 Apatite 10 Diamond
  • It is important that students create an understanding of the fundamental difference between weathering and erosion.
  • It is important that students develop an understanding that a chemical reaction takes place between the water and the rocks, as well as the carbonated water and the rocks.
  • The carbonated water simulates the dissolved carbon dioxide in rainwater or moisture from the air leading to the carbonation weathering process.
  • These online stores can provide the 4 rocks necessary for the lab: American Educational Products or Flinn Scientific.
  • Extensions:

o Some students may possibly be able to determine or research the reaction equations that represent the chemical weathering for each type of rock.

For the Student

Purpose

You will explore the differences between erosion, weathering, and chemical weathering. You will complete a lab experiment that creates chemical weathering on 4 different types of rocks and use the Mohs Hardness Test to record your results.

Background

Weathering is a set of physical, chemical, and biological processes that alter the physical and chemical state of rocks and soil at or near the earth’s surface. Chemical weathering is any of the various weathering processes that cause exposed rock to undergo chemical decomposition, changing the chemical and mineralogical composition of the rock. Erosion is the process by which the surface of the earth is worn away by the action of water, glaciers, winds, and waves.

Materials

  • 8 - 12oz plastic cups
  • 1 liter of carbonated/seltzer water
  • 3 small pieces of limestone
  • 3 small pieces of granite
  • 3 small pieces of marble
  • 3 small pieces of sandstone
  • 1 penny
  • 1 iron nail
  • 1 piece of quartz
  • 1 permanent marker
  • Chromebooks/tablets for individuals or groups

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • Wash your hands thoroughly before leaving the lab.
  • Follow your teacher’s instructions for clean-up of your materials.

Procedure

  1. Label the 8 cups in the following way:
    1. carbonated water limestone,
    2. water limestone
    3. carbonated water marble
    4. water marble
    5. carbonated water granite
    6. water granite
    7. carbonated water sandstone
    8. water sandstone
  2. For the cups that require carbonated water, fill the cups half way with carbonated water and place the correct rock in each cup.
  3. For the cups that require water, fill the cups half way with water and place the correct rock in each cup.
  4. Set a timer for 30 minutes. When 30 minutes has past you will need to record your observations for each cup in the data table.
  5. Set aside the remaining 4 rocks, 1 of each type, to be used for the Hardness test.
  6. Follow this link to read about the Mohs Hardness Scale/Test and then conduct the Mohs Harness Test on the remaining 4 rocks. Record your findings in the initial observation column in the data table.
  7. Refer back to the rocks after 30 minutes, after 24 hours, and again in 7 days.
  8. Clean up as directed by your teacher.

Observations

Record all predictions and observations including how the rocks feel, look, their hardness and visible minerals in the cup.

Rock Water Type Initial Observation 30 minutes 1 day 1 week
Limestone None

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Limestone Tap Water

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Limestone Seltzer Water

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Marble None

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Marble Tap Water

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Marble Seltzer

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Granite None

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Granite Tap Water

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Granite Seltzer

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Sandstone None

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Sandstone Tap Water

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Sandstone Seltzer

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Post-lab Questions

Use your tablet, laptop or Chromebook to answer the research questions below. Use your best judgment when choosing appropriate resources for researching the information.

  1. Research and identify a famous or well-known building/statue that uses the following types of rocks in its construction: limestone, granite, marble and sandstone.
  2. Given the following items to use to test the hardness of a rock: finger nail, a penny, an iron nail, and a piece of quartz; how could you determine the hardness of the limestone, marble, granite and sandstone?
  3. Use the Geology.com dictionary site to accurately explain the difference between erosion and chemical weathering.
  4. Watch this presentation from the National Park Service, then explain how carbon and chemical weathering are related.
  5. After 1 week of sitting in the water and carbonated water, what were the most important details that led you to understand that a chemical reaction was taking place?
  6. Why is it important to understand chemical weathering and its effects on different types of minerals?