Crystal Formation Task
By Megan Downie
All about crystals......
What is a crystal? Crystals are solids which are formed by a regular and predictable pattern of atoms and molecules bonding together. This special pattern causes the crystal to form all sorts of different shapes.
What substances can be used to make crystals? There are 4 main substances used to make crystals. Alum, Metal Crystals, Borax and Sugar.
What are some examples of crystals in nature? What household items can you grow
crystals from? Many types of crystals are found in nature. Mineral crystals are found deep within the Earth. They are most commonly grown near volcanic areas as the hot gases come across cool places, therefor forming a crystal. Snowflakes are also crystals, they are formed when the cold water crystallises due to the freezing temperatures. Diamonds and quarts are also found in nature. Common household
items you can use to make crystals are salt and sugar.
Explain the process of crystal growth The way that crystals grow is a process called nucleation. Nucleation usually starts working with the molecules. To grow a crystal, you need to make a strong solution which then maximizes the chances for the solution particles to come together and form a nucleus, which will then grow into your
crystal. Nucleation can then occur between the particles of the solution.
Nucleation usually works better on rough surfaces.
Explain how crystals can grow in different shapes, sizes and colours The shape of a crystal is determined by a repeating pattern of molecules and atoms. Each crystal is made up of a different number of molecules and atoms therefor each crystal will be a different size and shape. Many different types of chemicals are added to a crystal solution to make them a variety of different colours. It may also depend on how the atoms and molecules absorb the light.
Outline a few different types of crystals Covalent Crystals:. An example of this is a crystal is a diamond or zinc sulfide. Covalent crystals
can have high melting points. Metallic Crystals: Metallic crystals normally have high melting points. Ionic Crystals: This crystal is where an individual atom doesn’t have any bonds to form the crystal, but are held together by electrostatic forces. Sodium Chloride is an example of an ionic crystal. Ionic crystals have high melting points. Molecular Crystals: An example of a molecular crystal is sugar. Molecular crystals are usually soft and have low melting points. There are also, triclinic, monoclinic, orthorhombic, tetragonal, trigonal, hexagonal and cubic crystals.
What effect do crystals have on light travelling through them? When light travels through a crystal, it is refracted. In a crystal light bends towards the normal, the light also disperses in different directions.
What are the optimum conditions for crystal growth? The optimum growing conditions for crystals are warm places as it will evaporate the water/ solution quicker. Crystals can also grow in cooler temperatures, but it then takes longer for the water to evaporate.
2x 250ml beakers Filter funnel and filter paper Hot water Stirring rod, plastic spoon, spatula, tongs or tweezers Fine nylon thread Watch glass or paper hat Ruler Smart phone Diary to record observations
Method- Day 1
Tuesday Place 25g of potash alum in a 250ml or bigger beaker. Then add 170ml of hot water . Stir the mixture until the crystals have dissolved (it may appear cloudy/milky colour) Insert the filter paper and filter the warm solution Cover the beaker with the watch glass or fresh filter paper and set aside in a cool place- allow it to stand undisturbed overnight. Wash the first beaker and funnel.
Method- Day 2
Wednesday Observe the beaker solution; the bottom should be covered with a layer of smallish crystals. Carefully pour off the clear solution above the crystals into a clean beaker- set it aside for later, leaving the crystals behind in the other beaker If you come back and no crystals have been formed on the bottom of the beaker you now add your ‘seed’ crystals that you left over from the day before Let it stand over night
Method- Day 3
Thursday From the bed of crystals, one good symmetrical crystal or group of crystals needs to be selected to act as “seed” for your big crystal. Using a plastic spoon, spatula, tongs or tweezers, transfer the selected crystal to the beaker containing the decanted (poured out) solution, trying to place it centrally in the beaker.q This step is not essential, however, and good a crystal can usually be obtained just by leaving the crystal on the bottom of the beaker. Take a picture of the crystal, sized up next to a ruler; remember to mark how much solution is in the beaker. Record the date in a diary Cover the solution with a loose-fitting paper hat that permits water to evaporate slowly whilst keeping out dust. Allow the solution to stand, not in direct sunlight or near a heater. The aim is to keep the temperature as constant as possible.
Results- Day 1
Observations day 1 - solution appears clear.
Results- day 2
Observations day 2 - Solution still appears clear no crystals have formed, therefor I will start a whole new one tomorrow.
Results- Day 3
Observations day 3 - This is a whole new solution, it appears clear.
Results- September 20th
Observations September 20th - small granules of crystals have started to form. There are two crystals in the solution both sized at 1cm. The level of the solution in the beaker is 2.5cm.
Results- September 27th
Observations September 27th - not much has changed since September 20. There are still small granules in the solution and the crystal sizes has remained the same (1cm) . The liquid of the solution has remained at 2.5cm
Results- October 4th
Observations October 4th - One of the crystals has disappeared, this may be due to the amount of sunlight being exposed on the solution. The remaining crystal is still 1cm, there has been no growth so far. Although the amount of solution has been decreased, it has decreased down to 2cm of liquid.
My crystal grew very slowly, it didn't change size or shape at all throughout this project. I'm not quite sure why it didn't grow at all, but this is science and nothing is predictable! This photo captures the light being refracted within the crystal. You can see how the light makes the crystal glisten, the light disperses in different directions.
Liquid levels in the beaker- September 20th- 2.5cm. September 27th- 2.5cm. October 4th- 2cm. Final liquid level (October 13th)- 2cm.
Size of the crystal- September 20th- 1cm. September 27th- 1cm. October 4th- 1cm. Final Crystal (October 13th)- 1cm
Final dimensions- Height- 1cm Width- 0.3cm Length- 1.5cm
safety sheet - when working with crystals
Ducksters. (n.d.). Science for Kids. Retrieved 9 29, 2013, from Crystals: http://www.ducksters.com/science/crystals.php
Earth, T. D. (n.d.). Crystal Growth. Retrieved 9 30, 2013, from How do crystals grow: http://www.mnh.si.edu/earth/text/2_2_2_2.html
Web, K. (n.d.). Chemistry&New Zealand. Retrieved 10 1, 2013, from How do crystals form and how do they grow: http://www.chemistry.co.nz/crystals_forming.htm
Web, K. (n.d.). Chemistry&New Zealand. Retrieved 9 30, 2013, from What is a crystal: http://www.chemistry.co.nz/crystals_defined.htm
Web, K. (n.d.). Chemistry&New Zealand . Retrieved 10 10, 2013, from What types of crystals are there?:http://www.chemistry.co.nz/crystal_types.htm