Earth Science - Rock properties; Inquiry Process - Classification, observation, evidence, and reasoning to understand (3rd - 4th Grade)
This investigation explores rocks, their properties, and different ways to classify rocks. (Sample rock pictures)
Special materials - home made rocks need to be made a week before their are used. Takes one week to set and dry.
Recipe - Makes about 18 rocks with a 5 cm diameter Mix the flour, salt, and alum together
250 ml (1 cup) white flour
125 ml (1/2 cup) salt
10 ml (2 tsp) alum
125 ml (1/2 cup) water
5 drops red food coloring
5 drops blue food coloring
3 drops yellow food coloring
250 ml (1 cup) coarse sand
125 ml (1/2 cup) gravel - 2 different colors
30 ml (1/8 cup) oyster shell pieces
(What science says - enduring understanding, big ideas, generalizations)
Rocks are composed of Earth materials.
Describe properties of rocks.
(How science inquires - process, skill, methodolgy)
Properties can be used to identify and describe objects.
Make observations, identify properties/ characteristics and use them to describe objects.
Properties can be used to organize objects as similar or different and into groups with similar properties (classification).
Group and regroup rocks based on observed properties.
Possible Activity Sequence
Focus questions - What is a rock? What are the properties of rocks? From what are they made? How are they made?
Materials: Home made rocks, pick (nail) magnifying glass, paper plate, small vials to put separate parts of the home made rock in, lab notes
Summary - the home made rock was made from - gravel, sand, shells, flour, water, food coloring, alum, and salt. The flour and alum need not be specifically identified other than powder.
Using a paper clip for a scratch test. Depending on the rocks that you can find select four preferably the hardest quartz which will not be scratched by the paper clip.
Demonstrate how the paper clip scratch test on a piece of chalk.
Try the scratch test on four different rocks and order them by their hardness (calcite, quartz, gypsum, and fluorite) Use the paperclip, penny, and their finger nail).
Record data on the chart - for each tool write yes or no if it scratches the mineral. Write a summary of the results in the last column.
Mohs hardness = 1 - talc, 2 - gypsum, 3 - calcite, 4 - fluorite, 5 - apatite, 6 - orthoclase, 7 - quartz, 8 - topaz, 9 - corundum, 10 - diamond
Minerals are ingredients of which rocks are made. There are over 2 000 of them.
Calcite quest - calcite is the only mineral that makes bubbles with acid (vinegar). So they will take four rocks, put them in 25 ml of vinegar, let it stand 24 hours, and compare the results with a control of 25 ml of vinegar. The rock samples can be rinsed and reused several times.
Rocks to test - granite, limestone, marble, sandstone. Record which create bubbles.
Review properties of calcite - hardness, bubble, color... Do the vinegar test on calcite, remove liquid and evaporate it also.
Next day observe rocks are done fizzing and liquid... Pour liquid into an evaporation dish and set aside to observe later. Remember to include the vial that had only vinegar. Compare the vinegar only to the calcite (crystals) and the residue in the dishes for the other rocks.
Portland cement, limestone, seashells...
Minerals to investigate - mica, feldspar, quartz, hornblende, calcite, granite,
Create a lab sheet for each rock sample to record properties for each. Name, color, hardness, luster, other...
Challenge students to find the minerals in a piece of granite. (hornblende, feldspar, quartz, mica) (there will be no calcite, but they should do the test to see)
1. What is a rock?
[A rock is an earth material composed of one or more minerals. Rocks we have studied include granite, limestone, marble, and sand stone.] (recall)
2. Name some rocks we have studied.
3. What is a mineral?
[A mineral is a basic earth material, an ingredient in a rock that cannot be physically taken apart any further. Minerals we have studied include calcite, feldspar, fluorite, gypsum, hornblende, mica, and quartz.] (recall)
4. Name two minerals.
5. How can you tell mica and hornblende apart?
[Both are black, but mica has a special property. It pulls apart in paper-thin, flexible sheets. The hornblende looks more needle- like and fibrous.] (recall)
6. What were the minerals you found in granite?
[Mica, feldspar, quartz, and hornblende] (recall)
7. If you found a new rock, how would you find out what minerals were in it?
[Any and all of
the tests studied in the module: scratch test, acid test, looking
for specific properties] (integrating)
8. Why do you think people use granite to construct bridges, buildings, and monuments?
9. What do you think is the most interesting property of a rock or mineral we have investigated gated?
10. How do you think minerals get mixed together to make rocks?
(thematic connection: Interaction, Change)
11. If an author wrote that "a rock is like a chocolate chip cookie," what do you think the author had in mind?12. What would be a good use of a very hard mineral like quartz?
13. How would you find out the hardness of three minerals if you didn't have any tool with which to scratch them?
14. Suppose you found a brick near your school. How could you find out if calcite is an ingredient in the brick?
Table of materials found in the home made rock and its properties. Draw a picture of each rock material that is found in the first column, in the second describe its properties, and put additional notes in the third.
Draw the vial before and after settling.
Draw what was in the evaporating dish.
|Mineral||Paper clip||Penny||Finger nail||Tools that scratched this mineral|
Picture of rock
Possible kind of rock
fingernail _____ penny ______ paper clip _____ nothing _____
shiny ______ not shiny _____
Dr. Robert Sweetland's Notes ©