Keying Rocks 5 th Grade Kelley Dunbar, Mr. Bellamy and Mrs. Cargle

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1 References: (Checked 1/2005) Keying Rocks 5 th Grade Kelley Dunbar, Mr. Bellamy and Mrs. Cargle -- Rocks and Minerals -- Source of Rocks are Made of Minerals Benchmarks: Objectives: SLC 12: Identify characteristics and/or patterns in rocks and soil. Benchmark A: Students will classify rocks by their characteristics. SLC 1: Use a simple key to classify objects, organisms and/or phenomena Students will use a rock key to classify rocks into three types: igneous, sedimentary and metamorphic. Materials: Rocks and Minerals Packets & overheads Rock Charts & overhead Rocks (one per student) Like a Rock! Worksheet Initial Demonstration: Display at the front of the class several examples of each type of rock sedimentary, igneous and metamorphic. Have the students come up in groups to look at the rocks then return to their desks and write in their journals any similarities and differences they observed. Target Observations: More than likely, the students will not be able to discern how the rocks have been separated. They will probably notice only general similarities and differences among all the rocks. Target Model: Rocks can be classified in many different ways. The classification is not always obvious.

2 Procedure: Discuss their observations then let them know that the rocks are grouped according to the scientific classifications sedimentary, igneous and metamorphic which are based on how the rocks are formed. Pass out the Rocks and Minerals packets and use the overheads to help illustrate the different types of rocks, how they are formed, and how long they take to form. Show them the rock cycle and discuss how all the rocks are tied together; without one element the whole cycle would be thrown off. Mnemonics can be used to help the students remember how the names match the way the rocks are formed. Sedimentary rocks are formed from sediments, which are smaller rocks/sand. Igneous rocks are made from fire; we use the term ignite when talking about lighting a fire. Metamorphic rocks morphed from the other two types. Let the students choose a rock to identify. Pass out the Like a Rock! worksheet, along with magnifying glasses, and have them work on Tests 1 and 2 drawing a description of their rock. This will familiarize them with their rock s characteristics. To complete Test 3, hand out the Rock Chart and use the accompanying overhead to work with them to key the rock they have selected. Make sure to discuss the different attributes described in the rock chart and encourage the students to come up with explanations regarding why the different categories contain the attributes they do. For example, it should make sense that sedimentary rocks usually [have] pores between pieces because sedimentary rocks are composed of smaller bits of rocks/sand that have been pressed together. In the same way, it should make sense that metamorphic rocks rarely [have] pores or openings because they were once sedimentary or igneous rocks that changed under the influence of tremendous pressure. Be sure to discuss the difference between rocks and minerals (the minerals resource may be helpful). Students should understand that all rocks are made of minerals, but not all minerals are rocks. mineral: any natural occurring, inorganic (does not include carbon) substance Note: by this definition, water (H 2 O) is a mineral, but definitely NOT a rock! Target Observations: There are three types of rocks sedimentary, igneous and metamorphic. Target Revised Model: Rocks can be categorized by the way they are formed. Summary: Students know that rocks are classified as sedimentary, igneous, and metamorphic. They are also familiar with the characteristics of each type.

3 Like a Rock! Test 1: Description Look at your rock carefully. Look at the color, the crystals, and any other features. Draw your rock as detailed as you can below. Test 2: Magnification Use the hand lenses to look at your rock. Draw a detailed view of your rock under magnification.

4 Test 3: Identification Use the rock identification key to figure out if your rock is igneous, metamorphic, or sedimentary. Rock Type: Test 4: Hardness Here are the minerals Mohs used to determine his hardness scale: Diamond 10 Corundum 9 Topaz 8 Quartz 7 Orthoclase (Feldspar) 6 Aptite 5 Fluorite 4 Calcite 3 Gypsum 2 Talc 1

5 Find out how hard your rock is by trying these tests and seeing where it falls on the scale. If your rock Give it a hardness number Can be rubbed off on the fingers 1 Can be scratched with a fingernail 2 Can be scratched with a penny 3 Can be scratched easily with a butter knife 4 Is hard to scratch with a butter knife 5 Can be scratched with a steel nail but not glass 6 Can be used to scratch glass 7 Too hard to be tested in this scale 8-10 Scale Number: Which mineral from Mohs scale does your rock match up with? Test 5: The vinegar test Put your rock in a cup of vinegar. Let it sit for a while. Describe what happened. Test 6: The magnet test Use the magnet to test if your rock contains magnetic material. Describe what happened.