Biology/Chemistry

Rock Formation.

Therese Donatello	St. Edward School
	4343 W. Sunnyside
	CHICAGO IL 60630
	(773) 736-9133

Objective(s):

The Junior High student will be able to show how rocks are formed by cementation, compaction, and evaporation.

Materials:

EVAPORATION; Each group will need 2 test tubes, 40mL of water, 3-4 teaspoons of salt, 3-4 teaspoons sugar, 2 toothpicks, 2 pieces of string, and 2 plastic caps.

CEMENTATION; Each group will need 2 plastic cups, 1 jar large enough to hold the plastic cup, enough sand to fill the cup ¾ full, enough white glue to fill a cup ½ full, enough water to fill the cup with the glue, and a stick.

COMPACTION: Each group will need a pencil sharpener, 4-5 crayons of different colors, and a 12 inch piece of aluminum foil.

Strategy:

EVAPORATION:

A. Place 20 mL of water into each test tube. In one container add salt until no more will dissolve. In the other test tube add sugar until no more will dissolve.

B. Pour a thin layer of each solution into separate plastic caps.

C. Tie a string to one end of a toothpick and place the other end of the thread into the test tube so it doesn’t touch the sides or the bottom of the test tube.

D. Place the test tubes and the plastic caps where they will not be disturbed.

E. Check the solutions daily and record any changes.

CEMENTATION:

A. Poke small holes into the bottom of a plastic cup that will let a solution flow through but not the sand.

B. Fill a cup ¾ full of sand.

C. In a second cup mix ½ cup white glue with ½ cup water.

D. Suspend the cup with the sand over the jar.

E. Slowly pour the glue solution over the sand and allow it to drain through for several days.

F. Cut away the cup when the sand feels dry to the touch and record the results.

COMPACTION:

A. Use a pencil sharpener to make a pile of crayon shavings (use different colors to represent the different minerals) on a sheet of aluminum foil.

B. Fold the edges of the foil to make a rectangular packet.

C. Gently flatten the packet by squeezing it between your palms.

D. Unfold the packet and examine the “rock” that was formed.

E. Return the “rock” to the foil packet and stand on it. Then open and examine it again.

Performance Assessment:

The student should be able to answer the following questions.

A. In the evaporation experiment compare what happened to the thin layer solution and the solution in the test tube.

B. In the compaction experiment explain what kind of rock was formed giving at least three reasons.

C. In the compaction experiment explain what happened as more pressure was applied to the packet of crayon shavings.

D. Based on what you know about heat and rock formation what do you think would happen to a packet of crayon pieces that was heated on a hot plate for three or four minutes. Tell what the crayon pieces represent and what kind of rock was formed.

Conclusions:

The student will be able to explain the formation of rocks by the various methods described and infer the formation of other rocks when given information for another type of experiment.