By Charlotte Cunliffe
1. 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. 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. 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. Crystals are grown in a solution that can only hold a certain amount of solute. This is called the solubility 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. 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 may include; salt crystals, metallic crystals, ionic crystals, molecular crystals and covalent crystals. From this, you can have certain types of crystals such as emerald, amethyst and quartz.
7. 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.
· Two 250mL beakers
· Filter funnel and filter paper
· Stirring rod
Place 25g of potash alum in one beaker and add 170mL of hot water. Stir the mixture until all of the particles are dissolved.
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 fresh filter paper and set aside in a cool, sheltered place and allow it to stand overnight.
Checking that the crystal has grown. If not, then you can “seed”
the crystal and kick-start the growth.
· Clean beaker
· Nylon thread
· Pencil or Stirring rod
· Ruler – if possible
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. Take a picture of the crystal next to a ruler for the first stages of the crystal growth.
- The crystal liquid appeared clear, with a slightly clouded appearance.
- Before the alum was dissolved, there was small particles of crystals
- Nothing had happened over night, resulting in having to create new solution and 'seeding' it.
- After one night and after the 'seeding' process, small crystals had formed on the bottom of the jar that are no larger than 1 millimetre.
- On the first meausurement day, the solution level was at 3 centimetres, and the crystals were at about 1 millimetre.
- The crystals grew larger also
- The solution went down approximately half a centimetre.
- The crystals didn't show any signs of growing over the second week.
- Again, the solution only went down by half a centimetre.
- The crystals again didn't grow.
Work Sheet and Safety Sheet
Over the three weeks, my crystal hardly grew at all and only ended up with small molecules growing at the bottom of the beaker which looked like sugar granules. The small granules may have grown slightly, but would have been less than a millimetre.
My crystal ended up being millimetre in height, but over one centimetre in length, which was a result that I was somewhat happy with!
My photos illustrates somewhat how light travels through crystals. It also illustrates the different sizes of my crystal and the different dimensions of it also.