Growing Crystals

Madeleine Stretton

Method

Place approximately 25 g of potash alum in a beaker and add approximately 170 ml of hot water. Stir the mixture until all the crystals have dissolved. 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 undisturbed overnight.

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. Carefully 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. 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.

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 solution, trying to place it centrally in 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 a good crystal can usually be obtained just by leaving the crystal on the bottom of the beaker.)

Take a picture of the crystal, preferably close to a ruler so that you can measure its size, and mark the level of the liquid in the beaker. Record the date in your 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 in a draft free location, not in direct sunlight or near a heater. The aim is to keep the temperature as constant as possible.

Once a week record in your diary the level of the solution in the beaker and if possible, without disturbing your crystal, take a picture of it close to a ruler so that you can estimate how much it has grown. Try and avoid disturbing crystals during the growth phase as this may induce additional crystals to grow.

If small isolated crystals appear, you may be able to carefully remove them with tweezers. Be careful not to disturb your big crystal. If small crystals grow on the main crystal, remove it, dry it with tissues, and carefully remove the adhering buds. Do not touch the crystal with your fingers. The crystal is likely to be quite fragile, fairly brittle, and easily damaged, so should not be dropped or bumped.

When it is decided to terminate the experiment (after about 10 weeks or so), remove your crystal very carefully from the beaker, dry it with tissues and with a ruler measure its length, width and height. Compare the measurement, if you can, with the size of the original crystal.

To complete the artistic component, students will digitally photograph the completed crystal, and using the effects of light and shade, colour and other techniques, produce an artwork featuring the crystal and demonstrating the principles of diffraction/ reflection/ dispersion using light and or objects/images (see examples). The ingenuity of students will be encouraged to produce an innovative picture which highlights the crystal.

Questions

1. What is a crystal?

A piece of a homogeneous solid substance having a naturally geometrically regular form with symmetrically arranged plane faces.

    2. What substances can be used to make crystals?

Table of Common Chemicals for Growing Crystals

aluminum potassium sulfate

ammonium chloride

sodium borate

calcium chloride

sodium nitrate

copper acetate

copper sulfate

iron sulfate

potassium iodide

potassium chromium sulfate

potassium permanganate

sodium carbonate

sodium sulfate, anhydrous

sodium thiosulfate

cobalt chloride

ferric ammonium sulfate

magnesium sulfate

nickel sulfate

potassium chromate

potassium sodium tartrate

sodium ferrocyanide

sodium chloride

sucrose

sodium bicarbonate

sodium acetate

    3. What are some examples of crystals in nature?What household items can you also grow crystals from?

    Baking Soda

    Table Salt

    Epsom Salt

    4. Explain the process of crystal growth.

    When the chemicals are mixed and left to sit for a while, thy will create crystals.

    5. Explain how crystals can grow in different shapes and sizes.

    The crystal gets bigger the longer that you leave it to sit. They can grow in different shapes and sizes depending on how the conditions that you let your crystals sit in. If the temperature does not stay at a constant temperature for the whole experiment, your results will be altered slightly. If you keep your crystal in sunlight for the experiment, that will also change the result.

    6. Outline a few different types of crystals.

    Lots of other gemstones are also crystals and have been valued for many years. Crystals are valued for their rarity and beauty.Salt and Sugar are crystals also.

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

    Depending on the angle that light hits the crystal the way that it refracted. No two crystals will ever have light refracted the same way. bright light will be reflected back at you and it depends on the crystal, but sometimes the light can be blinding.

    8. What are the optimum conditions for crystal growth?

    it can depend on the type of crystal that you are trying to grow, but the best conditions are hot and sometimes humid temperatures. Vibration or moving the crystals will slow down the rate at which your crystal grows and sometimes even stop it altogether.

    9. Make a plan for next week (as a list);

    - Tuesday

    Place approximately 25 g of potash alum in a beaker and add approximately 170 ml of hot water. Stir the mixture until all the crystals have dissolved. 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 undisturbed overnight.

    - Wednesday

    Today we collect fill our jars with the crystals and solution and take them home to grow them over the holidays. We also finish doing the questions and do more on this assignment. Thursday is similar to Wednesday. More of the project.

I was in a group of three when we were making the crystals and there not too many big ones so we all took a couple of small ones and all of mine have managed to be quite sucessful. I have about 4 really big ones and a lot of much smaller ones.

I have made a word find about the materials that we used and some different types of crystals. It is not easy. The words are up and down. They are diagonal and left and right. The words are

Quartz

Brittle

Ruby

Fragile

Sapphire

Temperature

Apparatus

Ruler

Solution

Filter funnel

Crystal

Beaker

Potash Alum

Sulfur

Shattuckite

Topaz

Galaxyite

Tiger eye

Amber

Amethyst

Aura Quartz

Diamond

Emerald

Fluorite

Fossils

Glass

Garnet

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