SCIENCE YEAR 9
Crystals are solids formed by patterned molecules connecting together to create a rigid whole. In crystals a collection of atoms called the Unit Cell is repeated to create the arrangement of the crystal. The forming of crystals is called crystallization. Crystals form in nature when liquids cool and start to set. Molecules in the liquid gather together and attempt to become stable; they repeat this to create the patterns that form the crystal. In nature crystals can be formed by liquid rock called magma, as it cools slowly the crystals forms. Diamonds, Rubies and emeralds are formed this way.
Crystals found in nature can be snowflakes, ice crystal
that form in high clouds when water freezes. Timing crystals are when electric
currents are sent through a crystal making it vibrate at a certain frequency,
Quartz crystals are used in watches and other electronics.
Three household items that can create a crystal is salt, food colouring and water. Crystals form when liquids cool and start to harden. Molecules of liquid gather together becoming stable; they repeat a pattern as they form creating the crystals.
Crystals have a very flat surface called facets.
They can form shapes such as triangles, rectangles and squares. The shapes formed
are from the molecules and atoms that make up the crystal. There are seven
basic crystals shapes, cubic, trigonal, triclinic, orthorhombic, hexagonal,
tetragonal and monoclinic.
Quartz crystals get their colour from the environment around them. Amethyst crystals get their colour from iron found in the crystal’s structure, Topaz is an aluminium silicate its colours come from all the different chemicals. The colour compound depends on how the molecules adsorb the light.
Crystals have a high refractive index; this means the light inside them is bent and travels slower than in air. The high refractive index causes them to have internal reflection; jewelers often cut the crystals to create more internal reflection to make them look more amazing.
Warmth is the place for growing crystals, but not in direct sunlight. It’s ideal for the temperature to stay constant this is because when the crystals is being created you don’t want it to evaporate.
Tuesday: Session 1
- 2, 250mL Beakers
- Filter paper
- 25g potash alum
- Filter funnel
- Hot water
- Stirring rod
1. Put the 25g of potash alum in a beaker
2. Add 170mL of warm water
3. Stir the mixture until all the crystals have dissolved
4. With the Filter Funnel, filter the mixture with the filter paper into another beaker
5. Cover the beaker with some filter paper
6. Leave in a sheltered area over night.
Wednesday: Session 2
The bottom of the beaker should be covered in a small layer of crystals. If there is none continue with Session 2.
1. Add one spatula potash alum to the mixture
2. cover and leave over night
Thursday: Session 3
- 2, 250mL Beakers
1. The bottom of the beaker should be covered in crystals
2. Pour the liquid that is left into another beaker
3. From the bottom the other beaker choose a crystal to use as a starter (seed) for a bigger crystal
4. Take a picture of the crystal with a ruler next to it, marking the height of the liquid
5. Record the date
6. Cover the beaker and put back in sheltered area
Once we set up for our crystals to grow, all the potash alum has all dissolved. We left the beaker to sit overnight.
Once left over night our crystals hadn't managed to grow. A thin layer of tiny crystals covered the bottem. We re-set the creating of the crystals and left to sit overnight.
Observation: Day 7
The Crystals had formed a small layer of crust after a week. No one main crystal had formed.
After another week a few main crystals had formed, but not big enough to detach from the crust. The liquid had still not dried up either.