Crystal

Year 9Science

What is Crystal?

Crystal is

What can be used to make crystals?

Crystal can be made using

Crystals in nature

Household items you can use to grow crystals

crystal in nature

household items that can be used to grow crystals

Explain the process of crystal growth

How crystals can grow in different shapes and sizes

shapes and sizes

The process of crystal growth

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

effect of crystals on light

Making a crystal

Safety

Equipment  -make sure all apparatus is clean and dry. 

  • A measuring cylinder
  • A source of hot water
  • More than 25 g of potash alum
  • Two 250ml beakers
  • A stirring rod
  • A filter funnel and filter paper
  • Tweezers
  • Tongs
  • Spatula
  • Some fine nylon thread
  • A watch-glass or paper hat to fit on one of the beakers
  • A ruler
  • Smart phone or digital camera
  • A diary or log book to record observations

Day 1

  • Measure out approximately 170 ml of hot water.
  • Place 25 g of potash alum in a beaker.
    NB: don't use all the available alum as you may need it later on to 'seed' the solution.
  • Add the water to the beaker and stir the mixture until all the crystals have dissolved.
    NB: the solution may have a slightly cloudy appearance due to the impurities in the the technical grade of alum used.
  • Filter the warm solution trough a filter funnel (in which filter paper is inserted) into a clean beaker.
  • 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.
  • Wash and dry the first beaker, funnel and stirring rod and discard of the filter paper and residue.

Day 2

  • Observe the beaker and take a photo with a ruler.
  • A thin layer of crystals should have formed on the bottom of the beaker. If there is not a layer of crystals you can reseed the mixture.
  • Replace in a cool, sheltered place to stand understurbed overnight.

Day 3

  • Observe the beaker and take a photo with a ruler.
  • The layer of crystals should have grown further.
  • Carefully decant the clear solution above the crystal into a clean beaker, leaving the crystals behind, and set the solution aside for later.
  • From the bed of crystals select a good symetrical one to cultivate.
  • Tie one end of some nylon thread around the selected crystal, tie the other end around a pencil or skewer.
  • Balance the skewer or pencil on the rim of the beaker containing the solution so that the crystal is sitting in the solution (you may need to adjust the length of the nylon thread).
  • Cover the solution with a loose fitting paper hat that permits water to evaporate slowly yet keeps out dust.
  • Take another photo before replaceing the beaker in a cool, sheltered place to stand understurbed.

Tips

If small crystals appear carefully remove them with tweezers being careful not to disturb the large crystal. If small crystals grow on the main crystal, remove it, dry it with tissues and use tweezers to remove the buds. Do not touch the crystal with your fingers as it will be quite fragile. For this reason also do not knock the crystal.

Sometimes small crystals can be re-dissolved into the solution if you remove the large crystal and warm the beaker in a bath of warm water. Stir the solution gently while it is being warmed. Remove the beaker from the hot water as soon as the small crystals have dissolved. Allow the beaker to cool to room temperature. Replace the crystal and return the beaker to its original place.

When no further growth is apparent a new saturated solution can be formed as before. When the new solution is cool enough place your original crystal in the new solution and it should continue to grow.

Observations

Day 1

The water level

ruler measurement

notes

Day 2

The water level

ruler measurement

notes

Day 3

The water level

ruler measurement

notes

Day 4

The water level

ruler measurement

notes

Day 5

Day 5 observations and notes

Day 6

Day 6 observations and notes

Day 7

Day 7 observations and notes

Day 8

Day 8 observations and notes

Day 9

Day 9 observations and notes

Day 10

Day 10 observations and notes

Headline!

Day 11 observations and notes

Day 12

Day 12 observations and notes

Day 13

Day 13 observations and notes

Day 14

Day 14 observations and notes

Day 15

Day 15 observations and notes

Day 16

Day 16 observations and notes

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