By Durga Buchholz
What is a crystal?
Crystals are solids formed by a repeated pattern of molecules joining together.
What substances can be used to make crystals?
potassium sulfate (potassium alum)
ammonium chloridesodium borate (borax)
copper acetate (cupric acetate)
copper sulfate (cupric sulfate)
iron sulfate (ferrous sulfate)
potassium chromium sulfate (chrome alum)
sodium carbonate (washing soda)
sodium sulfate, anhydrous
What are some examples of crystals in nature? What household items can you also grow crystals from?
Some crystals grow in caves. You can grow crystals from table salt and Vaseline
Explain the process of crystal growth.
A crystal is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. Crystal growth is a major stage of a crystallization process and consists in the addition of new atoms, ions or polymer strings into the characteristic arrangement.
Explain how crystals can grow in different shapes and sizes.
Different crystals grow differently depending on the substances and where it is. The substances give the crystal it's colour. The process starts off at a hot and then cools.
Outline a few different types of crystals.
Some types include:
Triclinic - usually not symmetrical from one side to the other, which can lead to some fairly strange shapes
Monoclinic - like skewed tetragonal crystals, often forming prisms and double pyramids
Orthorhombic - like tetragonal crystals except not square in cross section (when viewing the crystal on end), forming rhombic prisms or dipyramids (two pyramids stuck together)
Tetragonal - similar to cubic crystals, but longer along one axis than the other, forming double pyramids and prisms
Trigonal - possess a single 3-fold axis of rotation instead of the 6-fold axis of the hexagonal division
Hexagonal - six-sided prisms. When you look at the crystal on-end, the cross section is a hexagon
Cubic - is not always cube shaped! You'll also find octahedrons (eight faces) and dodecahedrons (10 faces).
What effect do crystals have on light travelling through them? (relate to reflection, refraction, dispersion and diffraction)
The crystal is see-through. It refracts the light because of the way it is shaped.
What are the optimum conditions for crystal growth?
Allow the solution to stand in a draft free location, not in direct sunlight or near a heater.
Day I Brought It Home:
The jar has one small crystal at the bottom of the jar. Around it there are mini sugar like pieces.
Not much has changed since I brought my crystal home. It has all joined together to make a big, flat crystal on the bottom of the jar. Refer to picture 1.
The crystals have grown a bit bigger but not much.
No change. The crystals are exactly the same as last week. Refer picture 2.
School Term 4:
Around the 28th of October my crystal had started to grow a lot bigger and wider.
It has become more of a clump. They took much longer than anticipated.
My final picture (Refer picture 3) shows that my crystal is broken up into three little masses. The crystal did not change much over the holidays. But around week 2 term 4 it started to grow properly. The crystal is made up of many little crystals, then split into three masses. You can't really see any refraction in the crystals though. (refer to pictures 4 and 5)
Tuesday – method
Make sure all apparatus is clean and dry. Filter the solution into another clean beaker and cover. Put in a cool place and leave overnight. Place potash alum in a beaker (250ml) and add about 200 ml of hot water. Stir until the crystals dissolve.
Wednesday – method
The next day, we observed the beaker of solution. No crystals had formed so we had to repeat the process.
Thursday – method
This also failed, so we used someone else’s crystals.
No photos were taken because we had no crystals. But photo was taken when the crystal came home.