Investigating Rocks

Leah Bulver, WestWood Elementary, Prior Lake, Minnesota, based on an original activity from the Foss Kit, Earth Materials, pg. 11
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In this classroom guided inquiry lesson, students will become geologists. They will investigate rocks and the properties we can use to describe them. Students will observe, record, and reflect on their findings. They will record their observations in their science notebooks throughout the lesson. After the investigation, students will develop a hypothesis as to what they think rocks are made of. Students will draw a conclusion later on in the unit after they study minerals.

Learning Goals

This activity is designed for students to explore rocks and their properties. Students will make observations and write a hypothesis based on their investigation.
Key Concepts:
Students will learn that a geologist is a scientist who studies planet Earth. One thing that a geologist studies about Earth is its rocks. Rocks are among the materials that make up Earth.
Students will learn the properties a geologist would use to describe rocks.
Vocabulary Words: geology, geologist, property, circumference, diameter, depth, balance, mass, granite, igneous, plutonic

Context for Use

This lesson could be taught grades 2-4 (however, it could also be adjusted for upper and lower grades) with a class size between 20 to 25 students. This lesson can be done in a regular classroom space. Special equipment needed includes: a piece of granite for each group, paper plates, and hand lenses. This lesson is part of our 3rd grade Foss Science curriculum, however I decided to substitute granite instead of the mock rocks the unit suggests using. I feel that using a real rock rather than a man-made one with be more beneficial. This year I will be teaching in a 2nd/3rd grade multiage class, so I will be adapting it for 50 students.

Description and Teaching Materials

Materials Needed:
student science notebooks and pencils
10 chunks of granite
10 paper plates
25 hand lenses
25 measuring tapes
10 plastic cups
Student Response Sheet- Mock Rocks
Chart paper


1) Introduce geology to students by telling them that the study of materials that make up planet Earth is called geology. Then, explain to them what a geologist is. Then, explain that –ology is "the study of" and –ologist is "a person who studies". Then, discuss ento-, bio-, and geo-. Have the students combine the terms to realize the meaning of the words biology, entomologist, and geology. See if they can think of any others.

2) Introduce the idea of rock properties. Explain to students that geologists make detailed observations of rocks. Also, talk with students about the importance of careful and detailed observations. They need these because when they want to test a rock the rock has usually changed in some way and they want to be able to compare it to what it was like before the test. Make a list on chart paper of all the different properties a geologist could use to describe rocks, including: texture, color, shape, edges, size, weight, and maybe smell.

3) Introduce granite and explain to students that their challenge is to describe the rock in detail. Tell them that granite is an Igneous Rock, meaning that it is a volcanic rock. Draw a diagram to show them that it is a plutonic rock, coming from inside of the magma chamber.

4) Remind students to use their hand lenses to get an up-close view of their granite. They also can use their measuring tape to measure the size of their rock. They need to draw a detailed sketch of their rock in their Science Notebooks and write observation sentences. Have students get equipment and begin their observations.

5) To conclude today's lesson, have the students meet together as a large group. Share their observations they came up with. Have all the students write one question they are wondering about their rock. Make a "Questions about Rocks" chart. Have students share their questions and record them on the chart. Then, have students write a hypothesis of what a rock is. Share their hypotheses, and tell them we will come back to them throughout the unit. Their hypothesis of what a rock is may change throughout the unit.

6) If time allows, have students start a word bank including the key vocabulary words.

This lesson has been modified from Foss: Earth Materials, Investigation 1: Mock Rocks Part1: Investigating Mock Rocks. Published by Delta Education, Nashua, NH, 2000.

Teaching Notes and Tips

I have taught this lesson before, but this time we are not using the mock rocks- which are basically made of flour, salt, and alum. I feel that using real granite will make the lesson more realistic for students. One thing that might be helpful to do is model writing an observation in student notebooks so they know what your expectations are. One thing that I feel I have added to this lesson that it was missing from Foss was the hypothesis part. I want students to write what they are thinking a rock is at the end of the lesson. Now, I know they won't know yet what minerals make up granite, but I hope that all students observe that granite is made up of different materials.


I will assess students on this lesson through my observations throughout the activity along with collecting their science journals and checking their observation sentences, hypothesis, and word bank entries. I will also be assessing students' participation in class discussions and in their science groups.


Grade 1: Earth and Space Science: 1. Earth Processes and Structures: 3. Earth materials include solid rocks, sand, soil and water. These materials have different observable physical properties that make them useful. Group or classify rocks in terms of color, shape, and size.

References and Resources