Incredible, edible geology! - rock making

Instructor, May-June, 1996 by Lynne Kepler

Fun science is just a stone's throw away when you make rocks

My kids are collectors, and the things they most like to collect are rocks! There are chunky quartz conglomerates, colorful sandstones, and rocks that sparkle with quartz or pyrite. Some of their favorite rocks have been gathered from the gravel road near our home, while others were collected on trips. The kids look at these rocks over and over again. They compare their colors and feel their textures, noticing what makes each rock special. My kids are by no means the only kids on the block who love rocks; most kids get a kick out of them and will truly enjoy the experiment that follows.

ACTIVITY: EDIBLE ROCKS

Concept: Students will observe and describe the properties of rocks.

Skills: observing, classifying, measuring, communicating

Materials: rocks, cooking oil to spray on students' hands (the pump, non-aerosol kind works best), waxed paper (1 small piece per student), a wooden spoon, a hot plate, a large soup pot, bowls, plastic spoons, small cups, ingredients for edible rocks

Edible Rock Ingredients

(Makes approximately 24 rocks)

Bonding Ingredients: 80 large marshmallows, 6 tablespoons butter or margarine

Mineral Ingredients: 12 cups Rice Krispies, 2 cups nuts, 2 cups raisins or dried cranberries, 2 cups M&Ms, 2 cups chocolate chips

Vocabulary:

Minerals are inorganic (nonliving) chemical elements or compounds that can be found in the earth's crust. Minerals students may be familiar with are salt, talc, clay, and gemstones. Conglomerates are sedimentary rocks made up of pebbles that are cemented together.

Steps:

1 Provide students with rocks to examine. Include some such as granite, which have easy-to-see minerals. Encourage students to observe the rocks closely with a hand lens. Can they see separate components? (This will be a snap to see with some rocks, like conglomerates or a piece of granite, but will not be readily visible in other types of rocks, such as shale.) Which rocks are the heaviest? Lightest? Smoothest? Darkest? How are the rocks alike? How are they different?

2 Put each of the "mineral" ingredients, except the Rice Krispies, in separate bowls.

3 Before you begin cooking, explain that rocks are a combination of two or more minerals bonded together. Tell students that the Rice Krispies represent one of the minerals in their edible rocks. Then show them the other mineral ingredients.

4 Give each student a paper cup and a sheet of waxed paper, and tell students that they may choose two minerals and take one teaspoonful of each. These minerals will go in their cups.

5 Melt the butter and marshmallows in the pot. Note: Students should keep a safe distance from the hot plate and pot. The bonding mixture will be very hot!

6 Stir in the Rice Krispies and mix until they are coated with marshmallow. While you do this, kids should be spraying their hands with the oil.

7 Place about a 1/2 cup of the mixture on each student's waxed paper. Students should now add their other minerals, pressing all of the ingredients together to form an edible rock.

Younger Students: Reinforce the idea that rocks are made up of different minerals by comparing the different ingredients they used to make their edible rocks with the different minerals that make up a real rock. Have students observe, compare, and describe the individual edible rocks.

Older Students: In addition to having students make observations about their edible rocks, you can compare the process of how the edible rocks were formed (by heat and by pressure) with the concept of how real rocks are formed (by heat and pressure inside the earth). Invite students to investigate the difference between igneous, sedimentary, and metamorphic rocks.

8 Your students can celebrate their new understanding of rocks by munching down their rock creations.

A GEM OF A SCIENCE STATION

Amethysts, turquoise, emeralds, and agates are examples of gemstones. A gemstone is a mineral that is treasured for its beauty or rarity.

Here is a learning center idea that will have your students searching for buried treasure. Fill one or two plastic dishpans with sand. Bury gemstones in the sand. (See Resources for a gemstone supplier.) Make sifters by punching holes in the bottom of small plastic containers, like the kind cottage cheese comes in. Students use these sifters to scoop up some sand and pan for the hidden gemstones. Including field guides for identification of gemstones, hand lenses, and a balance will encourage students to extend their learning.

ACROSS THE CURRICULUM

Mixed-Up Minerals (math)

Give each student a 2-inch-square piece of light brown paper. Let students cut or tear edges to make a paper rock. On a piece of chart paper draw and label one column for each of the combinations that students could have created to make rocks (for example, chocolate chips and raisins, chocolate chips and nuts, and so on). Each student should write his or her name on the rock, then use a glue stick to add it to the column that describes it. Use the graph to create math problems.