Homemade Rocks
I whip up this recipe (DON"T eat it) with the biggest pot and spoon I can find.
2 cups course sand
1 cup of small gravel
2 cups flour (yes, like for baking)
1 cup water
½ cup rock salt
3 tablespoons alum
You can find alum at the grocery spice shelf. The others ingredients should be at your local nursery in 3 to 10 pound bags. Mix everything together and give the students generous equivalent lumps. Have students mold the mix into shapes they have seen in real rocks. They may make them into round smooth shapes or course, rough ones. Have each student make at least FIVE rocks. Have the students write predictions about what will change and occur. Each student receives a small cup that they label with their name to hold their rocks.
The next day:
Students may have only one of their rocks from their cup. Students write about the predictions they made yesterday . Show the students how to turn their verbal sentences into writing. Describe the mixture now. Is it hard or mushy? Is it dry or moist? Use complete sentences and include details.
The third day:
Click here to see a reproducible worksheet (free) for recording the trial data. On the third day conduct tests and trials to see how much hardening has occurred. Each student may only have one rock from their cup. (They should all have at least three more.)
1. Drop the rock from 1" . If the rock did not break;
2. Drop the rock from 2" If the rock did not break:
3. Drop the rock from 3" Etc until the rock breaks.
Who had the hardest rock of the day? Which rock fell from the highest distance without breaking? Students fill in the answers and squares on the worksheet. The students cut out their colored columns at the bottom of the blackline master and paste them to a chart for an instant graph.
On the fourth day we depart from the project for a day to allow the rocks to noticeably harden. Perhaps this could be done instead:
Materials: Construction paper, crayons, glue and sand. Have the students make pictures of the beach by mixing glue generously with the sand. Use the construction paper to decorate the sun, trees, treasure chest, families and clouds.
On the fifth day we repeat the trials from the third day. The results should be much more interesting the second time around. Each student may still only have one stone.
On the sixth day, answer the predictions from the first day. The students may have their remaining rock. What was the sequence of the changes? Why did the rocks fall and break differently on day 3 than in the trials on day 5?
To demonstrate completion of the rock cycle have the students try to break their rock. When they do, have them put the broken portions in a single petri dish half. Fill the rest of the dish with water. Ask the students to enter descriptions of the changes they notice in the broken "rock" material over the next two days.
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