In this activity, students will learn about the basics of earth chemistry. Students will investigate and analyze the composition of various minerals, while drawing connections to their chemistry content knowledge. Additionally, students will examine the chemical make-up of the earth’s crust and interpret associated data.
This activity will help prepare your students to meet the performance expectations in the following standards:
- HS-PS1-1: Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms.
- HS-ESS1-6: Apply scientific reasoning and evidence from ancient Earth materials, meteorites, and other planetary surfaces to construct an account of Earth’s formation and early history.
- Scientific and Engineering Practices:
- Analyzing and Interpreting Data
- Engaging in Argument from Evidence
By the end of this activity, students should be able to
- Understand that minerals are composed of two or more elements.
- Identify the specific elements that make up silicates.
- Interpret data provided regarding the abundancies of elements that make up elements found in the earth’s crust.
- Identify similarities between the structure and behavior of carbon containing compounds and silicon containing compounds.
This activity supports students’ understanding of
- Earth Chemistry
- Molecular Structure
- Chemical Formula
Teacher Preparation: 10 minutes
Lesson: 30-45 minutes
- Computer/Device with Internet access
- Student handout
- No specific safety precautions need to be observed for this activity.
- For more information about teaching Earth Chemistry in your chemistry classroom, read the associated Chemistry Solutions article, Teaching Earth Chemistry, published in September 2019.
- This activity is designed for use in a high school chemistry classroom.
- Students can complete this activity independently or in pairs.
- An answer key has been provided for teacher reference.
For the Student
- Find three chemical compounds that are made of only 2 ions that occur naturally. They will not only have a chemical name and formula, but also have a mineral name because this compound is found naturally on Earth.
- Using https://www.mindat.org/chemsearch.php select any 2 elements from the periodic table that might combine (a positive ion and a negative ion), and click the Search Minerals button.
- You will probably get lots more than just 2-ion minerals unless you exclude some or all (select Exclude Unselected) other elements.
- Record the formula and mineral name for your three minerals:
- Common minerals are listed in the table below:
(Don’t contain Mg or Fe)
(Contain Mg and/or Fe)
(Products of weathering reactions)
potassium feldspar, KAlSi3O8
sodium-rich plagioclase feldspar, NaAlSi3O8
muscovite mica, KAl2(Si3Al)O10(OH)2
calcium-rich plagioclase feldspar, CaAl2Si2O8
biotite mica, K(MgFe)3(Al,Fe)Si3O10(OH,F)2
- a. What elements do you find in all of these minerals?
*These 2 minerals together are called silica (quartz is 100% silica, while silica is just a part of the other minerals); compounds with these 2 elements are called silicates, so all of the minerals in this table are in that group.
- b. What other elements occur in these minerals in addition to the ones in part a?
- c. Look at the locations of these elements in the periodic table. What category of elements do they all belong?
- d. What element in these formulas occurs in the largest number, that is, has the larger subscripts?
- e. These minerals make up rocks; are you surprised that this element is so abundant in rocks? Explain.
- Examine the table below that describes the element abundances for the 8 most abundant elements in the Earth's crust.
|Element||Percentage by weight||Percentage by number of atoms||Percentage by volume|
|*Data source: Earth - Portrait of a Planet, by Stephen Marshak, W.W. Norton & Company, 2008.|
- a. What element is most abundant and does this agree with your findings in questions 2d above?
- b. Find the total percentage by weight, number of atoms, and volume for the combination of O and Si. Does this indicate silicates are a large part of the Earth's crust?
- c. Find the values for Si and O in an electronegativity table. Which one attracts electrons more?
- d. Thinking about what happens to the size of atoms when they gain electrons, how does this explain why O occupies such a high volume of the Earth's crust?
- e. Will the other six elements (Al through Mg) listed in the table gain or lose electrons when they combine with other elements? How does this explain their relative volume in the Earth's crust?
- The compounds we find in living things are generally called organic compounds and are based on C (with H and O), while minerals are by definition inorganic, and we have seen many of those are based on Si (with O). What does the position of C and Si in the periodic table tell you about their chemical behavior? Are they likely similar or different?
- Read the information and examine sample shapes of inorganic silicates from This Old Earth. Describe and give the name of the shape for the silica ion, SiO44.
*Note this shape repeats in many ways in the descriptions and diagrams on this web page.
- Examine some sample shapes of organic molecules by scrolling down the Lumen Biology webpage. Are there a large variety of shapes for carbon molecule structures?
- Do silicates and carbon seem to be acting in some similar ways to create molecules? Explain.
- Given the many shapes of minerals containing silica, would you guess that these molecules typically have weak or strong intermolecular forces between them?
*Keep this in mind as we will later see that this has an effect on volcano behavior.