TOPIC: TESTING FOR HARDNESS
To demonstrate how the hardness of a mineral can be determined
Variety of rocks, fingernail, penny, glass, knife, nail file
Scratch a mineral to measure its hardness by moving a sharp edge of the known object over the mineral to be tested. Then run a moistened fingertip over the surface to remove any loose powder. Think of some everyday objects other than rocks to test for hardness.
Look to see if the mineral has been scratched. The hardness scale, invented by Friedreich Mohs is divided into 10 degrees of hardness. Can a mineral can be scratched with a knife blade but not with a copper coin? If so its hardness must be between 3.5 and 5.5. Record the results of the test. You can later use the results of your test minerals to test the hardness of other minerals. Make a sketch of your observations and label.
Any mineral can scratch another one of the same hardness or softer than itself.
Adapted from experiment in Rocks and Fossils by Ray Oliver
TOPIC: Testing for Density and Specific Gravity
To demonstrate how the density of a material can be determined
Variety of rocks, graduated cylinder, pan or beam balance
Find the mass (g) of a rock by balancing it on a pan or beam balance. Find the volume (v) of a rock by finding the amount of water it displaces in a graduated cylinder. Divide the mass by the volume to arrive at its density (D) Divide the density by 1 to arrive at the mineral’s specific gravity. How many other ordinary materials can you think of to test for density?
Do all rocks of similar volume have a similar mass? How is specific gravity related to density? Record your results, make a sketch of your observations and label.
Mass is the amount of matter in an object. Volume is the amount of space something takes up. Density is mass per unit volume. Density allows us to compare one substance to another even though the amounts of mass and volume are different. Specific gravity is the density of a substance compared to the density of water which is always 1.