Activity 1
Objective: to observe the properties of two substances with different kinds of bonds.
Materials:
three metal teaspoons
magnifying glass
matches
2 cm table salt
2 cm table sugar
folded paper towel hot pad
Procedure:
-
1. Rub a few grains of the salt and then the sugar between your fingers. Which one feels the sharpest or the roughest?
-
2. Examine with the magnifying glass a few grains of both salt and sugar. Describe the grain shape of each.
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3. Put some of the salt in a spoon. Crush it with the other spoon. Do the same with some of the sugar. Which is the most difficult to crush?
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4. Light a match or a candle. Hold the teaspoon of salt over the flame for ten seconds. Does it melt? Do the same with a teaspoon of sugar. Which substance appears to have the higher melting temperature?
Record all of your data in the chart below as you do each test.
Characteristics
|
Table Salt
|
Table Sugar
|
Roughness
Grain Shape
Hardness
Melting point
Questions:
-
1. Use your book to find out what kind of bonds salt and sugar have.
-
2. Which of these two substances appears to have the stronger bonds?
Activity 2
Objective: to familiarize students with the shapes of crystals in their three dimensional forms.
Materials:
pencil
crystal model outline sheets,1 and 2
scissors
tape
drawing paper
Procedure:
-
1. Look at drawings of the six basic crystal shapes. Draw and label each one on drawing paper.
-
2. Using the outline sheet cut out each crystal pattern. Fold along the dotted lines and tape the edges. Identify each shape using your drawings done in part 1.
(figure available in print form)
(figure available in print form)
Activity 3
Objective: to demonstrate in concrete fashion the relationship between atomic arrangement and crystal shape.
Materials:
12 one inch size styrofoam balls
12 one-half inch size styrofoam balls
green crayons or paint
toothpicks
salt
magnifying glass
Procedure:
-
1. Color the large styrofoam balls green to represent chlorine atoms. The smaller size balls will represent sodium atoms.
-
2. Break a toothpick in half, push one end into the chlorine and the other end into the sodium. Do this to all the “atoms” you have. Now you have sodium chloride molecules.
-
3. Using the toothpick halves join one NaCl (sodium chloride) molecule to another, matching up sodium to chlorine each time, and at right angles to one another. They should be placed as tightly together as possible. Look at the diagram to get an idea of how it should look.
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4. Sprinkle some of the salt grains on a dark surface and inspect them with the magnifying glass. What shape are they? What is the chemical name for this compound?
(figure available in print form)
Questions:
-
1. What shape is the salt crystal?
-
2. What shape does the styrofoam ball model of the atoms have?
-
3. Is there a relationship between the answers to questions 1 and 2? Why?
Activity 4
Objective: to understand the meaning of specific gravity by determining the specific gravities of several mineral samples experimentally.
Materials:
thread or string
water
250 ml beaker
spring scale
mineral samples:
pyrite
quartzite
galena
others
Procedure:
-
1. Tie a twelve inch length of thread to the first sample, then tie the other end to the spring scale. Record the mass on the chart.
-
2. Fill the beaker about two-thirds full with the water. Submerge the sample in the water being careful not to allow the mineral to touch the bottom or sides of the beaker. Record the mass on the chart.
-
3. Subtract the mass in water from the mass in air. This is the “loss of mass in water.” Record this on the chart.
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4. The “loss of mass in water” amount is the same as the mass of water displaced. Enter this on the chart.
-
5. Use the formula below to calculate the specific gravity of your mineral.
-
____
Specific gravity = mass of the mineral in air / mass of the water displaced by the mineral
-
6. Repeat steps 1-5 for each of the samples available.
-
DATA CHART
|
Pyrite
|
Quartzite
|
Galena
|
Unknown Sample
|
mass in air
mass in water
loss of mass
in water
mass of water
displaced
specific gravity
Questions:
-
1. Pyrite is called fool’s gold. How can you tell it from real gold?
-
2. What is an alloy and how can you differentiate it from a pure sample?
-
3. Use the
Handbook of Physics and Chemistry
to find the material with the highest and lowest specific gravity.
Activity 5
Objective: to determine density of solids using the direct measurement of the volume of the solid.
Materials:
assortment of blocks:
pine
balsa wood
styrofoam
ceramic tile
steel plate
metric ruler
balance beam scale
Procedure:
-
1. Carefully measure the length, width, and thickness of the block using the metric ruler. Fill in the table below with your results.
-
2. Calculate the volume by multiplying the three numbers and enter the results in the designated space.
-
3. Use the balance beam scale to determine the mass of the block in grams. Enter the result in the designated space.
-
4. Calculate the density and record your answer.
-
____
Density = mass volume
-
5. Repeat the above procedure for all of the blocks and carefully record all of the measurements and results of calculations.
-
pine
|
balsa
|
styrofoam
|
tile
|
steel
|
bark
|
wood
|
|
square
|
plate
|
length
width
thickness
volume
mass
density
Questions:
-
1. What is the definition of density?
-
2. Could you use this technique to determine the density of a toy soldier? Why?
-
3. Could you use this density formula to find the density of a steel ball? How?
Activity 6
Objective: to determine the density of an irregularly-shaped solid using the displacement method.
Materials:
balsa wood block
metal plate
small stone
metric ruler
thread
balance beam scale
graduated cylinder
250 ml. beaker of water
paper towels
Directions: We have measured the density directly by using a ruler to find the volume of a regularly-shaped object. We can determine the density of an irregularly-shaped object using the displacement method. We will weigh the object on the scale to find mass; then we will use the graduated cylinder to find out how much water is displaced by the object when it is submerged. The amount of water displaced is the same as the volume of the object. Then we have only to put the numbers in our formula:
Density = mass / volume
*Important Information:
one milliliter = one cubic centimeter
1 ml = 1 cm3
Procedure:
-
1. Weigh the three objects. Record the data on the chart below.
-
2. Fill the graduated cylinder to the 50 ml. line with water from your beaker.
-
3. Securely tie each object with a 30 cm. length of thread.
-
4. Submerge one of the objects in the graduated cylinder. Record the new water level on the chart below. Repeat for each object.
-
5. Subtract the first reading (50 ml.) from the second reading. This is the
volume displaced
, or the volume of the object.
-
6. Divide the mass by the volume to find the density. Remember 1 ml. = 1 cm.
3
balsa wood
|
metal plate
|
stone
|
mass
second reading:
water and object
first reading
water only
volume displaced
density
Activity 7
Objective: to develop skills in mineral identification using some characteristics of minerals.
Materials:
-
mineral samples
-
penny
-
steel nail
-
hardened file
-
streak plate
-
compass
-
paper towels
-
lemon juice or dilute hydrochloric acid (Use acid
only
on samples kept at demonstration table — do
not
contaminate your samples at your desk.)
Procedure:
-
1. Read each mineral identification characteristic and use the suggested term or property to describe the mineral you are examining. Repeat for each mineral.
-
2. Characteristics:
Color: apparent external color: black, brown, gray-white, brownish-white, etc.
Luster: describes the shine or light-reflection from a mineral: metallic, pearly, greasy, glassy, silky.
Hardness: describes the resistance to scratching and is measured by the Mohs scale of hardness, #1 to #10, softest to hardest. To test hardness, scratch your sample with the following items in order. When a visible scratch is made (a dent in the rock), that is the hardness.
2.5 — fingernail
3 — penny
4-5 — steel file
6 — hardened file
over 7 — may scratch a streak plate but leaves no color
Streak: Describes the color of the powdered mineral. The streak can have a different color from the external apparent color. It is determined by rubbing the sample firmly over the plate, the color on the plate is the streak. A mineral of hardness 7 or over will have no streak, but may scratch the plate instead.
Magnetism: minerals that are magnetic will cause a compass needle to spin.
Crystal structure: Use your paper crystal models to determine the crystal shape of your sample.
Acid test: put one or two drops of a weak acid on your sample (be sure to use the samples on the demonstration table). If the mineral bubbles and fizzes it contains carbonate. The gas being released is carbon dioxide.
Heft: refers to the weight per volume or size. Terms that could be used would be “heavy,” “medium,” or “light.” These are only relative and imprecise terms but useful for comparing with specific gravity.
(figure available in print form)