Investigating the Rock Cycle: Looking at similarities and differences in rocks in the rock cycle.

• Students will make observations using characteristics like luster, crystal size, color, cleavage, hardness, density, and streak.
• Students will develop a testable hypothesis by analyzing their observations.
• Students will write up a possible experiment that they could run to test their hypothesis.

This activity is designed for an 8th grade classroom of around 25 - 30 students, although it could easily be expanded to a larger setting and a higher grade level. It is an inquiry-based lab where the students use what they know to develop ideas on how rocks could form. It will last 40-45 min by the time you get the students going. They may need more time if you have larger class sizes. Students should have some prior knowledge on mineral characteristics and how they can test those characteristics. The material that they will need would be a hardness test kit, hand lens or magnifying lens, a scale, and a graduated cylinder large enough to find the volume of the rocks used.

In this activity students will investigate the differences between Sedimentary, Igneous, and Metamorphic rocks. They will also look at the conditions in which these three rock types form and the characteristics of the rock that are developed from those conditions. On the board when the students come into the classroom they will see the question, what is the rock cycle?, on the board. In their science notebook they will, to the best of their current knowledge, write down what they think the rock cycle is. This will take about 5-10 min. Students will then be broken into groups of three and given three rocks. These three rocks with be one from each of the three rock types. The students will not be told what the rocks are or where on the rock cycle they belong. Students can name the three rocks if they wish or they can just be labeled 1-3. Students will then be given 15-20 min to look at their rocks and to describe as much about them as they can. They will have a hardness test kit, hand lens or magnifying lens, a scale, and a graduated cylinder large enough to find the volume of the rocks to use if they would like to. Once they have done this they will be asked to develop a hypothesis on how each rock formed. We will then get together as a class and report back on what their hypotheses are. This should not take long, probably 2-3 min. Once all groups have reported, then I will choose one of their rocks and have them write up what clues lead them to their hypothesis and how might they test their hypothesis. This will take the rest of the hour and is their homework for the night. They should come to class the next day with a paragraph on how they would test their experiment and what they would need to do so. We will go over the rock cycle in class the next day where they will be able to see if they had correctly determined the origin of the rock and learn more about how rocks are made or modified by our earth.

Students are going to want the teacher to give them the answers. It is important that the instructor purely guides them and does not give them the answers. If they are using the scale, they will need to make sure it is properly zeroed and is working correctly. If you are using glass graduated cylinders the students need to be reminded not to drop the rocks in, but to slide them down the side so they do not crack the bottom. The students should also be reminded of proper procedure if something glass is to break in your classroom.

This activity is different than what I would normally do in my class. I usually go over the rock cycle in detail and then show them examples of each of the different rock types. This activity now reverses this and has the students see if they can figure out what is going on.

Observations will be made of each student as students are working in their groups as to if they are completing the tasks they were given, and actively participating in the activity. The group will need to produce a hypothesis for each of their rocks as to how they formed and in the end turn in a written paragraph on how they would test one of their hypothesizes.

8.III.A.3 Processes of the rock cycle
8.III.A.6 Classifying rocks and minerals
8.I.B.1 Understanding of scientific investigations