By Morgan Price
What is as crystal?
A crystal is a solid object which is made up of a pattern of the same molecules.
What substances can be used to make crystals?
-Solvent (e.g. water)
-Solute (e.g. rock salt, Epsom salt or sugar)
- A range of chemicals, including but not limited to:
- Potassium alum
- Sodium borate
- Calcium chloride
- Sodium nitrate
- Copper acetate
What are some examples of crystals in nature? What household items can you also grow crystals from?
Some examples of crystals in nature are snowflakes, diamonds and table salt. Some household items that you can grow crystals from are sugar or salt and water.
Explain the process of crystal growth.
Crystals often form in nature when liquid cools down and begins to harden. Particular molecules in the liquid join together as they try to become stable. This happens in a repeating pattern, forming the crystals. To grow a crystal, there is a different process called nucleation. The molecules of the solute and solvent attempt to stick together, despite other forces in the solution trying to keep them apart. Every so often, a solute and solvent will stay together long enough to attract another molecule and so on, forming a crystal.
Explain how crystals can grow in different shapes and sizes.
When it comes to crystals growing in different shapes and sizes It can depend on some factors:
- The internal symmetry of the crystal
- The relative growth rates
- The different atoms and molecules making the crystals differs their shape
Outline a few different types of crystals.
-Covalent Crystals - Covalent crystals have a real chemical covalent between all of the atoms.
-Metallic Crystals - Metallic crystals have individual metal atoms sit on lattice sites while the outer electrons from these atoms are able to flow freely around the lattice.
-Ionic Crystals -Ionic crystals are individual atoms don't have covalent bonds between them but are held together by electrostatic forces.
-Molecular Crystals - there are recognisable molecules in the structure and are held together by non-covalent interactions like van der Waals forces or hydrogen bonding.
What effect do crystals have on light travelling through them? (Relate to reflection, refraction, dispersion and diffraction)
Most crystals are known to polarize light,although some can have the optic results of x-ray diffraction.
Tuesday 17th of September, 2013
-25g potash alum
-170mL hot water
-2 x 250mL beakers
Put 25g of potash alum and 170mL of hot water in a 250mL beaker. Stir until all is dissolved. Filter the solution through a filer funnel with filter paper inserted into another beaker. Cover with watch glass or fresh filter paper and allow to stand over night undisturbed. Record level of solution and take a photo.
Wednesday 18th of September, 2013
Observe changes in solution. Carefully decant the clear solution above crystals into clean beaker and set aside. Leave the crystals in the other beaker. Allow to stand overnight undisturbed. Record level of solution and take a picture.
Thursday 19th of September, 2013
Observe formation of crystals. Using a spatula, transfer a good symmetrical crystal to the beaker containing the decanted solution, aiming to place it centrally. Take a photo and mark the level of the solution on the beaker. Cover the solution with a loose-fitting paper hat. Allow beaker to stand undisturbed.
My crystals did grow but not as big as some peoples. I didn't think they'd grown as much as they had until i took them out of the jar. Overall my crystals did grow to a good size and at a good pace. The liquid levels halved every week that i observed my crystals, but when i took the crystals out of the jar all of the solution was not gone. St that start my crystals grew at a rather slow pace but as the weeks went on they got bigger and bigger. At the end of the experiment they were around two or three times as big as they were at the start.