M A K I N G  A  C R Y S T A L

Year 9 Science

A B O U T  C R Y S T A L S

1. WAT IS A CRYSTAL
Crystals are solid material where
ions, atoms and molecules fit together in a repeated pattern. These different
patterns cause the material of the crystal to form unique shapes. The charge of
a crystal is neutral in order for it to grow and form.

2. WHAT SUBSTANCES BE USED TO MAKE CRYSTALS

Naturally formed crystals can take millions of years to form once the liquid inside the Earth has cooled and hardened. Crystals made from human commonly take shorter amount of time and they can be made out of salts, ice and dry ice such as sodium chloride and various metals.

3. EXAMPLES OF CRYSTALS IN NATURE

Crystals are grown naturally deep within different surfaces, such as rock caves and the Earth’s surface. They can grow is mineral rich solutions in spacious areas such as rock cavities or molten rock.

4. PROCESS OF CRYSTAL GROWTH

Crystals are grown in a solution that can only hold a certain amount of solute.
This is called the soulibility of a solution. When the temperature of the solution is increased, hot water dissolves more solid substance than the cold water. This is because heated water molecules tent to move farther apart, making room for more solid substance to dissolve as well. When no more of the solid substance can be
dissolved, the solution is then called ‘saturated’. As this solution cools, the water molecules then move closer together again and there's less room for the solution to hold onto the dissolved solid. 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 on conditions, it may grow many small crystals or one large crystal.

5. HOW CRYSTALS GROW IN DIFFERENT SHAPES AND SIZES

Crystals grow into certain shapes, sizes and colours because the atoms or molecules join together in a certain pattern that repeats itself over and over to create a certain
shape. A crystal grows by adding atoms or molecules to all its sides in the exact same pattern as the atoms and molecules that were added before this. Because each different crystal is made up of a different building block (atom or molecule) they each have a different structure, shape and colour. Also depending on the growing conditions, the crystal grows at different speed and may affect the resulting size.

6. DIFFERENT TYPES OF CRYSTALS

Different types of crystals may include; salt crystals, metallic crystals, ionic crystals, molecular crystals and covalent crystals.

7. EFFECT CRYSTALS HAVE ON LIGHT

When light travels through a crystal, it is refracted. When travelling from a less dense medium into a crystal, the light bends towards the normal. When the light exits the crystal, because of the many faces, the light disperses in different directions.

8. The optimum growing
conditions are warm surroundings, including warm solution and warm air
temperature. Crystals will still grow in cooler temperatures, but it will take
longer for the water to evaporate. Crystal growth also requires light but the
crystals will eventually grow in the dark, but it will take a very long
time.


T U E S D A Y

Materials

· Two 250mL beakers

· Filter funnel and filter paper

· Stirring rod

Method

· Place 25g of potash alum in one beaker and add 170mL of hot water.
Stir the mixture until all of the particles are dissolved. (Note- Don’t use all
the alum).

· Then, filter the warm solution through a filter funnel (in which filter
paper has been inserted) into another clean beaker. Cover the beaker of
solution with r fresh filter paper and set aside in a cool, sheltered place and
allow it to stand overnight.

W E D N E S D A Y
Materials

· Clean beaker

· Tweezers

· Nylon thread

· Pencil or Stirring rod

· Ruler – if possible

Method

· Observe the beaker, and look for any major changes. The bottom should be
layered with a small layer of crystals which formed while the solution cooled.

· Carefully pour the clear solution above the crystals into a clean beaker
and set it aside for later.

·From the bed of crystals, one crystal needs to be selected as “seed” for
the main crystal. Using the tweezers, transfer the selected “seed” crystal into
the beaker containing the used solution whilst trying to place it centrally in
the beaker. A technique to promote growth is to suspend the crystal with a
nylon thread tied round a stirring rod or pencil resting on the rim of the
beaker. This step is not essential.

· Take a picture of the crystal next to a ruler for the first stages of
the crystal growth.


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