`CrystalsTherese Donatello              Archbishop Weber H. S.                               5252 W. Palmer St.                               Chicago IL 60639                               (312) 637-7500Objectives:The Jr. High students will be able to:1.  Identify  patterns in solids.2.  Compare the patterns to basic models of the six crystal systems.3.  Distinguish the various crystals that make up rocks.4.  Realize that gem stones are usually made from minerals and sometimes     from rocks.Materials Needed:large mineral specimens                      eye droppersrock specimens                               watermagnifying glasses                           stereoscopesstereo pictures of rocks, minerals & gems    stereo glasseslarge & small styrofoam balls                toothpickssodium chloride                              scissorsepsom salts                                  glueglass slides                                 thumbtackscandles                                      cardboardmatches                                      petri dishforceps                                      beads of various sizesStategy:1.  Review of solids    a. Place a petri dish containing different sizes of beads on the overhead        projector.    b. Ask the students how the particles would move in a gas, a liquid, and a        solid.    c. When the particles in the solid are moving slowly show how they start       arranging themselves into an orderly pattern.  Tell them this orderly        pattern is seen in solids called crystals.    d. Point out that particles in a solid are held close together in fixed       positions by forces that are stronger than those between particles in       a liquid or a gas.2.  Patterns    a. Using 4 large and 4 small styrofoam balls have the students attach them       to each other with toothpicks so that no 2 balls of the same size are       attached to each other.    b. Ask the students to name the shape of the structure created.    c. Ask them to arrange the balls again into a different structure.    d. Ask them what shape the second structure would have if they used more        balls in the same way.    e. Make sure that they see a pattern in the structures they make.3.  Crystal formation    a. Using forceps take one pinch of sodium chloride and place it on the        slide.  On another slide do the same thing with the epsom salts.    b. Observe each material under the stereoscope.    c. Draw the structures seen on each slide.    d. Using an eye dropper place a drop of water on each slide and stir until       the solid dissolves.    e. Light the candle with the match and using forceps to hold the slide       gently heat the slide until the water evaporates.    f. Observe each slide again.  Then draw the structures again and compare       them to the original drawings.    g. Point out that the crystal patterns are the same but the sizes may        differ.4.  Crystal systems    a. Cut out the patterns for the 6 crystal systems and fold and glue them to        form three dimensional figures.    b. Cut out the pattern for the contact goniometer and glue it to the        cardboard.  Attach the pointer to the measuring part with a thumbtack.    c. Place one side of the goniometer on one side of the crystal model and       the pointer on an adjacent side.  Read the angle on the goniometer.    d. Crystal system angles       (1) The isometric, orthorhombic, and tetragonal systems have 90 degree           angles.       (2) The hexagonal system has 60 degree angles.       (3) The monoclinic system has two 90 degree angles and on oblique            angle.       (4) The triclinic system has three oblique angles.5.  Crystal comparisons    a. Take a large quartz crystal and count the number of sides and measure        the angles between two adjacent sides using the goniometer.    b. Compare the readings for the models and determine what system quartz       belongs.    c. Do the same thing for the calcite crystal.6.  Stereo pictures    a. Place each lens of the stereo glasses over the same section of each       picture.    b. Move the lenses to match the distance between your eyes.  The pictures       should look 3 dimensional.  Ask if they can see the number of sides and       angles on the pictures of minerals.    c. Look at pictures of rocks in the same manner.  Ask if the crystals in        the rocks all look the same.  They should not look the same since rocks        are mixtures of minerals.    d. Look at pictures of gems in the same way.  Ask if they think gems are       rocks or minerals.  Most are minerals since the properties will be the        same.  This makes it easier to work with the material.7.  Identifying crystals in rocks    a. Using a magnifying glass look at a piece of granite.  Ask if any of the       crystals compare to the models studied previously.  They should be able       to see the quartz crystals.    b. Do the same thing with marble.  They should be able to distinguish       calcite.Performance Assessment:Samples have been brought back from the recently discovered planet "Olympia".Your job is to set up a plan by which you can: (1) classify the samples as minerals or rocks; (2) place any crystals in the correct crystal system.Students should have plans that show that various minerals make up rocks andby measuring the angles on the crystals and then comparing them to the crystalmodels they can be placed in the correct system.References:Horowitz, Irving.  Earth Science Investigations.  Amsco School Publications,Inc. New York: 1973`