BACKGROUND:
Minerals are pure substances. In this sense, pure
means that they are always composed of the same element or groups of
elements (compounds). Pure can be explained to the students is several ways:
- all of the same substance;
- no matter which way you cut something it always
looks the same;
- composed of the same molecules; or
- unmixed with any other matter.
Salt water, for example is not pure because it is
made up of salts and water. If you took the salt out, then you would
have a pure water.
Minerals are the ingredients of rocks. They are
like building blocks. Rocks are not pure substances, unless they are
composed of the same mineral.
PROCEDURE:
- A good way to illustrate this is to get three balls of different
colored clays. Each color by itself is "pure," like a mineral.
Red ball of clay is equivalent to a red mineral. A blue ball of clay is
equivalent to a blue mineral. No matter which way you "cut"
the ball of clay, it will be that pure color. If you put a little of the
blue and red minerals together, you have created a rock. Minerals make
up rocks.
- One way scientists observe things by looking for "KEY
CHARACTERISTICS," which are the fundamental, unchanging properties
of whatever is under study. Explain "KEY CHARACTERISTICS" to
the students by using the following or other examples:
When you go home today will your mom or dad recognize you? Yes, but how
will she/he recognize you?
If you take a friend home, will your mom know you from your
friend? What is the difference between you and your friend? The
difference can be called "characteristics." What about 20
years from now, will you look the same? No, but kind of yes? What
characteristics about you will never change? These would be key
characteristics.
- In this writing exercise, the students will begin to describe minerals
using a new set of vocabulary words. Have them write down the vocabulary
words as you put them on the board, and discuss what they mean using the
mineral specimens. Use the following specimens from the kit to explain
each word in the vocabulary list. If you have better specimens, use them
instead.
QUARTZ, FLUORITE, PYRITE - These minerals are crystals.
GYPSUM - This mineral is so soft that you can scratch it
with your fingernail.
QUARTZ, FLUORITE, PYRITE, GALENA, HEMATITE - These minerals are hard,
you cannot scratch them with your fingernail or a penny.
GALENA, PYRITE, HEMATITE - These minerals are very dense.
They are heavy.
ULEXITE, CALCITE, GYPSUM - These minerals are not very dense.
They are light.
MICA - This mineral is very flat.
ULEXITE, CALCITE - These minerals make the picture that is under
the mineral, do funny things. This is an optical property.
Ulexite brings the picture up toward you, like a television. Calcite
makes two images.
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