This is the new updated edition of the first book in the bestselling Uncovering Student Ideas in Science series. Like the first edition of volume 1, this book helps pinpoint what your students know (or think they know) so you can monitor their learning and adjust your teaching accordingly. Loaded with classroom-friendly features you can use immediately, the book includes 25 “probes”—brief, easily administered formative assessments designed to understand your students’ thinking about 60 core science concepts.

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The purpose of this assessment probe is to elicit students’ ideas about rocks. The probe is designed to determine whether students recognize that rock is not a term for size and that rocks can come in many sizes and shapes.

Justified list

Rock, minerals, Earth materials, grain size

All of the items on the list could be a rock. Simply, a rock is defined as any solid mass of mineral or mineral-like matter that occurs naturally as part of our planet and is formed over a long period of time (Lutgens and Tarbuck 2003). Rocks can be made up of one mineral or can be made up of two or more minerals. Rocks can be described by their size and shape. Rocks can range from huge boulders to single grains of sand and rock dust formed through the process of weathering. They can be jagged or smooth. Words like boulder, gravel, and sand have specific scientific meanings related to the average size of rock fragments. Rocks can be broken and shaped by natural weathering processes or broken, cut, and shaped by humans, resulting in a variety of sizes and shapes. Sediments can contain very tiny pieces of weathered rock.

Elementary Students

Younger elementary students become familiar with their immediate surroundings, including the variety of rocks found in their local environment. Students observe the different shapes and sizes rocks come in. In upper elementary grades, students can observe details of rocks and can use magnifiers to identify grains of the rock material in sand. Students learn that the solid materials formed by Earth are rocks, soil, and sediments and that these make up a part of Earth called the geosphere. They learn that other Earth systems interact with the geosphere, such as water in the hydrosphere or air in the atmosphere wearing away rock into smaller pieces that can be moved around.

Middle School Students

Middle school students learn how rocks are formed, shaped, and broken apart by the action of both abrupt and slow natural processes. They begin to tie these processes to the idea of a rock cycle. They develop an understanding that sediments contain small particles of rock and that these sediments can be cemented together again to form solid rock. They develop an understanding of how landforms such as mountains are formed through the uplift of rock or the hardening of molten lava from volcanoes. They learn how these landforms break down into rocks of different sizes and shapes, including grains of sand found on beaches made from volcanic rock or rock from distant mountains.

High School Students

Students use ideas about rocks to understand the history of Earth and its formations and the structure of the interior of Earth. They refine and deepen their understanding of the rock cycle.

This probe can be used with students in grades 3–8. Make sure students are familiar with the objects and materials on the list. It may be helpful to have props that show items on the list, including a picture of a large boulder. This probe can also be administered as a card sort. Place the words and/or pictures of the items on cards and ask students to sort them by “rock,” “not rock,” or “unsure” and to provide an explanation for each sorting decision.

• Children often fail to recognize that words like boulder, gravel, sand, and clay have specific meanings related to the average size of fragments. For example, children think of clay as being sticky, orange stuff found underground rather than as a very fine particle of rock (Driver et al. 1994).
• Freyberg (1985) found that the word rock is used in many different ways in our common language, contributing to the confusion over what a rock is geologically. Many students think rocks have particular size, not too large and not too small, rather than being characterized by what they are made of.
• Studies by Happs (1982, 1985) revealed that younger students often identify rocks by their weight, hardness, color, and jaggedness. Therefore, some students believe that rocks are larger, heavier, and more jagged than stones. They have difficulty with the idea of rock types being a range of sizes. They use words such as boulder, gravel, sand, and clay in ways related to where they are found, rather than seeing them as rocks of different sizes. For example, they say that boulders are larger than rocks and have rolled down a slope, gravel is something on the side of roads, sand is on beaches and in the desert, and clay is red and underground.

Plummer, D., and W. Kulman. 2005. Rocks in our pockets. Science Scope 29 (2): 60–61.

Rivet, A. E. 2017. Core idea ESS2: Earth’s systems. In Disciplinary core ideas: Reshaping teaching and learning, ed. R. G. Duncan, J. Krajcik, and A. E. Rivet, 205–223. Arlington, VA: NSTA Press.

Trundle, K., H. Miller, and L. Krissek. 2013. Digging into rocks with young children. Science and Children 50 (8): 46–51.

Varelas, M., and J. Benhart. 2004. Welcome to rock day. Science and Children 40 (1): 40–45.

• Younger students should be given ample opportunities to collect and examine a variety of rocks of different sizes and describe them according to their observable properties, while noting that they are all part of a group of Earth materials called rocks.
• When elementary students describe physical properties of objects, include rocks as objects in their study of properties of matter. Have students observe that rocks come in different sizes, shapes, colors, and textures.
• Provide opportunities for students to see that rocks can break down into very small pieces, including “rock dust.” This can be observed by rubbing two rocks together or filling a clean metal can with a few rocks and shaking it for an extended period of time. The dust comes from the pieces of mechanically weathered rock. Ask students what the dust is; encourage them to make the connection that it came from the rock and thus is the same material.
• Compare and contrast different types of beach sand that contains rocks and minerals, and trace their origin. For example, the white quartz in some sands may have come from pieces of granite rock that were further weathered into mineral particles. Volcanic beach sand comes from the weathering of volcanic rock.
• In 1922, geologist Chester Wentworth developed a classification chart for the size of rocks and their particles. This chart can be viewed on the Planetary Society’s website at www.planetary.org/multimedia/ space-images/charts/wentworth-1922-grainsize. html. Have students sort the rocks listed on the probe by decreasing size and compare their chart with Wentworth’s.