|
Growing crystals is a fun way to explore your
interest in chemistry and geology. There are lots of types of crystals
that can be grown from common household substances, such as sugar
(sucrose), salt (sodium chloride), epsom salts, borax, and alum.
Sometimes it's interesting to mix different materials to see what types
of crystals result. For example, salt crystals look different when they
are grown with vinegar. Can you figure out why?
If you want a good science fair project, it would be better if you
tested some aspect of growing crystals rather than simply growing pretty
crystals and explaining the process. Here are some ideas of ways to turn
a fun project into a great science fair or research project:
-
How does the rate of evaporation of the crystal-growing medium
affect the final size of the crystals? You can change the rate of
evaporation by sealing the container (no evaporation at all if there
is no air space) or by blowing a fan over the liquid or enclosing
the jar of medium with a dessicant.
Different places and seasons will have different
humidities. The crystals grown in a desert may be different from those
grown in a rain forest.
- You will usually heat water or another liquid
to dissolve a solid to grow your crystals. Does the rate at which
this liquid is cooled affect the way the crystals grow? You can
compare crystals allowed to cool at room temperature to those formed
from cooling the liquid in a refrigerator.
- What effect do additives have on the crystals?
You could add food coloring, flavorings, or other 'impurities'. How
do crystals grown from uniodized salt compare with those grown from
iodized salt?
- What steps can you take to maximize crystal
size? Developing a procedure is a form of experimental science. You
can affect parameters such as vibration, humidity, temperature, rate
of evaporation, purity of your growth medium, and time allowed for
crystal growth. The type of container used to grow your crystals may
make a difference, as could the type of string used to suspend a
seed crystal (or other method used to grow a crystal). Are you
changing containers when crystals start to grow that could compete
with your seed crystal? There are lots of things to think about!
Some may have a major effect on crystal growth and others may be
negligible. Does light/dark affect growth? Probably not for a salt
crystal, but it could for a substance that is degraded by visible
radiation.
- If you are up for a challenge, you can make
predictions about the shapes of crystals before you grow them, based
on their molecular structures and molecular geometry
|