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Hands-on science: (no lab required).

PREDICT

The Mohs hardness scale * uses an object's resistance to scratching to rank the hardness of minerals. How will the items in the materials list below rank on the scale? * Teachers, find the Mohs hardness scale in the activity on TE6.

MATERIALS

stainless steel spoon * copper penny * chalk * rock * bolt * glass jar * ceramic tile ** ** Be sure to only use materials that you don't mind leaving scratch marks on. Feel free to add any other rocks or household items whose hardness you would like to test.

DIRECTIONS

1) Divide into groups of three or four.

2) On a separate piece of paper, make a data table with an equal number of rows and columns. Label the first column "Test Object." Write "spoon" in the row below that, and "penny" in the third row down. Continue labeling the rows in the first column with the names of the rest of the objects to be tested.

3) Label the second column "spoon" and the third column "penny." Continue labeling the columns with the names of the rest of the objects.

4) Using the spoon, try to scratch the surface of the penny. Wipe any residue off the surface of the penny and observe: Did the spoon make any scratch marks on the penny? If so, write a "Yes" in the data-table cell beneath "penny." If the spoon did not scratch the penny, write "No."

5) Continue scratching the rest of the objects with the spoon and marking the results in the cells beneath the corresponding objects as you go along.

6) Repeat steps 4 and 5 with the rest of the objects in the first column. Record your results in the appropriate rows in the data table.

CONCLUSIONS

1) Using your data table, can you determine which object was the softest? List your test objects in order from softest to hardest.

2) The Mohs hardness scale goes from 1, for the softest minerals, to 10, for the hardest. If a penny has a hardness of 3.5 and a ceramic tile has a hardness of 7, where do you think the glass jar lies on this scale? What do you think chalk's hardness is on this scale?

3) If you were going rock hunting and could bring three household items to test the hardness of the rocks that you find, which three would you bring? Why?

[ILLUSTRATION OMITTED]

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Publication:Science World
Geographic Code:1USA
Date:Jan 6, 2010
Words:395
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