Crystallization

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Crystallization
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Content of PowerPoint

• Introduction
• What is crystals?
• Crystals produced by crystallization
• Procedure of crystallization

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Introduction of Crystallization

• Crystal is a solid body.
• The formation of a crystal is called
  crystallization.
•  Crystals are grown in many shapes.
• In order for crystallization to take place a
  solution must be "super saturated".

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• Crystallization is a technique.
• Its a process of formation of solid from
  solution.
• This can be done by various methods
• On the following slides we are going to
  introduce more about crystallization.

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What are Crystals?

• A crystal is a solid
• Fluid substances form crystals when they undergo
  a process of solidification.
• Most metals encountered in everyday life are poly
  crystals.
• Crystals are often symmetrically intergrown to
  form crystal twins.
• Crystal structure will form depends on the
  chemistry of the fluid
• The process of forming a crystalline structure
  is often referred to as crystallization.
• Crystallography is the scientific study of
  crystals and crystal formation.

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Common crystals produced by Crystallization
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Quartz Crystal Crystallography
Hexagonal Chemical Composition Silicon Dioxide
Hardness 7 Quartz is one of the most abundant
minerals in the world. Sand is mostly comprised
of quartz even the dust in the air is high in
quartz content. The most well-known form of
quartz is clear rock crystal, and it may be found
throughout the world. Particularly fine specimens
are currently found in Brazil, the United States
etc. The largest single quartz crystal recorded
was approximately 20 feet long and weighed more
than 48 tons.
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Bismuth Crystal Chemistry Bi Crystallography
Hexagonal Crystal Growth and Habits Bismuth
often forms crystals in parallel groups or as
hoppers.  It can also be reticulated, or
granular. Color and optical properties Silver
white with a slightly golden hue.  It tarnishes
to produce an iridescence.  Opaque Hardness 2 -
2.5 Occurance Native Bismuth is a rare mineral
that occurs in hydrothermal deposits associated
with cobalt, nickel, silver and tin.  It is also
found in pegmatites  and in topaz  bearing tin
and tungsten veins. Mineral Name From the German
wismuth, meaning white mass.
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Insulin Crystals
Gallium Crystal
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The Procedure of Crystallization
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How are crystals grown?
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When the temperature of the solution is
increased, hot water can dissolve more solid
substance than cold water. As a saturated
solution cools, the water molecules move closer
together again and there's less room for the
solution to hold onto as much of the dissolved
solid.
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Crystals begin to form and build on one another
as the water lets go of the excess solute. This
process is called recrystallization and,
depending upon conditions, one may obtain a mass
of many small crystals or one large crystal.
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How do crystals form and how do we control
its
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During recrystallization, crystals start growing
by a process called "nucleation". Particles of
dust on the surface of the solution can initiate
crystallization. However, this situation is
somewhat uncontrolled.
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To get controlled growth, a "seed crystal" is
tied on a piece of thread and is submerged in the
solution. As the temperature of the solution
continues to drop, more crystals will accumulate
on the thread.
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The rate at which crystallization occurs will
affect crystal quality. The best crystals are the
ones that grow SLOWLY.
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Cut a piece of thread of 20 cm long.
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Tie the seed crystal on the thread.
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Tie the thread to the vial cap.
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Adjust the length of the thread making sure that
the crystal does not touch the bottom of the vial
and dangles inside the vial.
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Get the warm saturated solution of the crystal
that you want to grow.
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Pour the saturated solutions into your vial.
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When the solution has come to near room
temperature, or when you see crystals start to
form on the bottom of the vial, gently place the
seed crystal in the solution.
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Allow the vial to sit undisturbed.
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Group Members

• F.3A
• Andrea Choi (11)
• Hannie Choi (12)
• Jane Chu (13)
• Claudia Fan (14)
• Samantha Ip (15)

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THE END