Making Sedimentary Rocks

Note: This is another extension of our geology unit. This lab comes shortly after the igneous rock lab and simulates how sedimentary rocks form. It is just a demonstration of the processes involved in the formation of sedimentary rocks, though it can be modified (different amounts of glue, dry vs. moist environments) to be a full fledged science experiment

Grade levels: 2-6

Demonstration:

Supplies: Styrofoam or paper cups, sand, popsicle sticks or disposable spoons

Step 1: Fill an 8 oz. cup about 1/3 full with sand
Step 2: Slowly add glue until the sand/glue mixture has a peanut butterish texture - not runny or too liquidy
Step 3: Use a wooden block or the bottom of another cup/glass to compact the sand glue mix as much as possible.
Step 4: Leave the cup in a dry area for approximately two weeks


Things to look out for:
1. Too much glue is the most common problem. It will take a much longer time to turn into a rock if too much glue is used.
2. Add more sand if things get too runny.
3. It usually takes about two weeks to harden, but sometimes longer
4. After the mixture hardens into a sandstone, you'll need to tear away the cup. Paper cups are the easiest to tear away.

Make an igneous rock

Note: There are a variety of recipes for this on the internet. I have used several, most recently this one from The Accidental Scientist. It gives much more thorough directions and includes more details on sugar, crystals, and the rock candy process. My students and I have never really followed the directions to the tee, but eventually, we always get rocks.

This is part of a geology unit that focuses on the rock cycle. Creating rock candy is supposed to simulate the creation of igneous rocks. We create a solution, like magma, by boiling the water and sugar, then letting it cool. It usually takes a while for it to turn into a rock, so we introduced a new variable to see if rapid cooling made a difference.

Grade levels: 4-8

Problem: Which will make better crystals, a solution placed in the freezer or one that is air dried?

Hypothesis:

Experiment:
Supplies: Package of sugar, cups, water, pencil or straw, string, washer or fishing weight

Part I:
A) Bring 2 cups of water to a boil
B) Mix in 4 cups of sugar until it is dissolved completely

Part II:
A) Tie string to the middle of a pencil or straw.
B) Tie washer to the other end of the string.
C) Pour sugar water into cup.
D) Put one sample in freezer and one sample at room temperature.
E) Wait (It's going to take a while - weeks, not days).

(pictures coming)

Results:

	Freezer Cup	Room Temp. Cup
Observation 1
Observation 2
Observation 3

Conclusion:

Possible Errors/Things to look out for
1. Put wax paper or a towel over the top of your cups - mold will grow in them eventually.
2. It may take up to 4 weeks to actually see crystals, just let it sit.
3. Leave it in a lab, it will stink after a while.
4. I do this with 6th graders - they often have trouble tying the string on the straw.
5. Due to the mold factor, I wouldn't suggest eating anything that has been out for several weeks.