Crystals

Zoe's crystal experiment

Final photo of crystal

Crystal Method

DAY 1: Tuesday

Materials

· 25 g of potash alum

· 2 beakers (250 ml or bigger)

· 170 ml of hot water

· Filter Funnel

· Filter Paper or Watch Glass

Make sure all apparatus is clean and dry.

1. Place approximately 25 g of potash alum in a beaker (250 ml or bigger) and add approximately 170 ml of hot water.

2. Stir the mixture until all the crystals have dissolved. The solution may have a slightly cloudy or milky appearance due to impurities in the technical grade of alum used.
NOTE: Don't use all the alum you have been given – keep a few crystals back in reserve in case you need to “seed” the solution later.

3. Filter the warm solution through a filter funnel (in which filter paper has been inserted) into another clean beaker.

4. Cover the beaker of solution with the watch glass or fresh filter paper and set aside in a cool sheltered place and allow it to stand undisturbed overnight. The first beaker and funnel can be washed and dried and the residue and filter paper used for filtration discarded.

DAY 2: Wednesday

Materials

· Beakers

· Stirring Rod

1. The next day, observe the beaker of solution. The bottom should have become covered with a layer of smallish crystals which formed spontaneously as the solution cooled.

2. Pour off the clear solution above the crystals into a clean beaker and set it aside for later, leaving the crystals behind in the other beaker. If for any reason, no crystals have formed after leaving the solution to stand overnight, the solution can be “seeded” by adding a crystal from the original alum.

3. Let it stand overnight again and observe the formation of crystals. Alternatively, if nothing has happened, crystal growth may also be induced by scratching the bottom of the glass beaker with a glass stirring rod.

DAY 3: Thursday

Materials

· Plastic Spoon/Spatula/tongs/tweezers

· Beakers

· Nylon thread

· Stirring rod

1. 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.

2. Using a plastic spoon, spatula, tongs or tweezers, transfer the selected crystal to the beaker containing the decanted solution, trying to place it in the centre of the beaker. A good technique to promote uniform growth is to suspend the crystal with a nylon thread tied round a stirring rod or pencil resting on the rim of the beaker. 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.

Crystal Information

1) What is a crystal?

They are solids that are formed by a regular repeated pattern of molecules connecting together.
2) What substances can be used to make crystals?
Chrome Alum Crystal-
potassium chromium sulphate and boiling water
Epsom Salt Crystal Needles- Epsom salt and hot tap water.
Borax Crystals- borax and boiling water.

3) What are some examples of crystals in nature? What household items can you also grow crystals from?
Common crystals in nature include snowflakes and diamonds. Crystals that are items in your household are table salt. To make crystals in other ways you can use sugar, cotton thread, Vaseline, ammonia, water etc.

4) Explain the process of the crystal growth?
The forming of crystals is called crystallization. Crystals often form in nature when the liquids cool and start to harden. Some molecules in the liquid gather together as they try to become stable. This pattern repeats and in the end it forms a crystal.

5) Explain how crystals can grow in different shapes and sizes.
This depends on 2 factors: Either the internal symmetry of the crystal or the relative growth rates along the many directions in the crystal.


6) Outline a few different types of crystals?
Sugar Crystals- An edible sugar crystal.
Borax Crystals- Naturally clear crystals that grow into pipe-cleaner shapes.
Copper Sulphate Crystals- they form blue diamonds. They are really easy to grow.


7) What effect do crystals have on light travelling through them? (Relate to reflection, refraction, dispersion and diffraction)

Crystals behaves like a 3-dimensional diffraction grating. This gives rise to both constructive and destructive interference effects in the diffraction pattern, such that it appears on the indicator as a series of separate spots which are known as reflections. The reflections contains information on all of the atoms in the structure and equally each atom gives the power of each reflection.

8) What are the optimum conditions for crystal growth?
Room temperature in an airtight container. Make sure there are no vibrations because it will slow down or stop the process of crystal growth.

Crystal wordsearch

MSDS (Materials Safety Data Sheet)

Photos

This is when we measured out the potash alum.
This is when we filtered the solution.
When you filter the solution it takes a long time.
This is how much solution we ended up with.
This is what my crystals look like.

Final crystal

My crystal grew only a little bit. During the 2 weeks there were more crystals forming but they didn't really grow in size.

Table of crystal size and liquid levels over 2 weeks

WEEK Liquid levels Crystal size
1 4cm 1cm
2 1cm 2cm

My liquid levels went down a lot. This happened because I put it in a place where it got quite hot. So the water evaporated by mistake.

This is the final measurement of the crystal.

Bibliography

- Why do different crystals have . (1998-2011). Retrieved August 31st, 2013, from Kiwi web: http://www.chemistry.co.nz/crystals_shapes.htm

- Crystal growing experiments. (2013). Retrieved August 31st, 2013, from Sciencecompany: http://www.sciencecompany.com/Crystal-Growing-Exp...

- What is a crystal? (1998-2011). Retrieved August 31st, 2013, from Kiwi web: http://www.chemistrt.co.nz/crystals_defined.htm

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