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Chemical Weathering of Rocks Mark as Favorite (1 Favorite)

LAB in Observations, Chemical Change, Interdisciplinary, Chemical Change, Acid Rain. Last updated July 12, 2018.

Summary

In this lab, students will explore simulated reactions that contribute to chemical weathering of certain rocks as it appears in nature. They will compare the effects of two different chemicals as it contacts various rock and mineral samples.

Grade Level

Elementary school

Objectives

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

  • Describe chemical weathering.
  • Explain their observations during chemical reactions with various types of rocks and minerals.
  • Discuss the potential effects of chemical weathering.

Chemistry Topics

  • Chemical Reactions
  • Chemical Change
  • Observations

Time

Teacher Preparation: 15 minutes

Lesson: about 30 minutes

Materials

  • 8 plastic/glass jars per group (or plate with an edge to hold in liquid)
  • lemon juice (a few tablespoons for each group)
  • vinegar (a few tablespoons for each group)
  • medicine droppers (2 for each group)
  • two pieces each of sandstone, limestone, calcite, chalk, and quartz for each group

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.
  • Do not consume lab solutions, even if they’re otherwise edible products.

Teacher Notes

  • Allow ample time during experiment for students to discuss their observations with their small groups. They will use the information they discussed to write a response in their notebooks or in provided space of the student handout.
  • Encourage students to think about the real-world connection for these small-scale reactions.
  • What should happen during the experiment: Lemon juice and vinegar are both weak acids. The lemon juice contains citric acid and the vinegar contains acetic acid. These mild acids will chemical react with rocks that contain calcium carbonate. The lemon juice and vinegar should have bubbled (fizzed) on the limestone, calcite, and chalk, which all contain calcium carbonate. There should not be a reaction on the quartz, which does not contain calcium carbonate. Explain that water commonly contains weak acids that react with rocks containing calcium carbonate and other minerals.
  • These reactions are supposed to mimic the chemical weathering that occurs in nature. Discuss the observations that indicate a chemical change has occurred with your students.

For the Student

Lesson

Materials

  • 2 jars or plates
  • lemon juice in a dropper bottle
  • vinegar in a dropper bottle
  • 2 pieces of limestone
  • 2 pieces of calcite
  • 2 pieces of chalk
  • 2 pieces of quartz

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.
  • Do not consume lab solutions, even if they’re otherwise edible products.

Procedure

  1. Label one jar/plate as “vinegar” and the other jar/plate as “lemon juice.”
  2. Place one of each type of rock in each jar, so that the jars each contain 4 rocks, one of each type.
  3. Put 2-3 drops of vinegar on one of the rock samples in the vinegar jar. Record your observations in the data table below, be sure to look and listen when recording your observations.
  4. Repeat step 3 with each of the remaining rock samples.
  5. Put 2-3 drops of lemon juice on one of the rock samples in the lemon juice jar. Record your observations in the data table below, be sure to look and listen when recording your observations.
  6. Repeat step 5 with each of the remaining rock samples.

Observations

Type of Rock Vinegar Lemon Juice
Limestone
Calcite
Chalk
Quartz

Analysis

  1. Did the lemon juice and vinegar react the same way on each rock?
  2. Why did some of the rocks react differently?
  3. What does this experiment have to do with chemical weathering?

Conclusion

Write a reflection entry including your observations for each rock, based on the discussion questions you went over during your lab investigation. Try to think about how you think the reactions in this experiment could affect the real world (ex: nature, buildings, etc.) Feel free to include drawings, narratives, or poems along with your scientific observation.