What is a crystal?
Crystals are a special type of solid material where the molecules fit together in a repeating pattern. The pattern of the molecules causes the crystals to form unique shapes.
What substances can be used to make crystals?
There are many different substances used to create crystals.
-Potassium alum and many other chemicals
Examples of crystals that are in nature:
- Ice Crystals
- Stalagmites & Stalactites
- Mineral crystals
In nature, crystals can from when liquid rock, called magma, cools. If it cools slowly enough crystals can form. Diamonds, rubies and emeralds are formed this way. Another way crystals form is when water evaporates from a mixture. Salt crystals often form as salt water evaporates.
What household items can you grow crystals from?
-Table salt, sugar and baking soda can be used to grow crystals.
Explain the process of crystal growth:
The process of forming crystals is called crystallization. Crystals often form in nature when liquids cool and start to harden. Certain molecules in the liquid gather together as they attempt to become stable. This pattern repeats and eventually forms a crystal.
Explain how crystals can grow in different shapes and sizes:
Crystals grow into certain shapes because the atoms or molecules join together in a pattern that repeats itself over and over to create a certain shape. A crystal grows by adding atoms or molecules to all its sides in the exact same pattern as the atoms and molecules that were added before. Because each different crystal is made up of a different building block (atom or molecule) they each have a different structure or shape.
Outline a few different types of crystals:
What effect do crystals have on light travelling through them? (relate to reflection, refraction, dispersion and diffraction)
Light behaves differently depending on which direction the light is reflecting at the crystal. The refractive index depends on both composition and the structure of the crystal. When light hits a crystal at a certain point, there will be a reflection of bright light. Sometimes the light can be blinding, but it depends on the crystal.
Ex. Diamond has a high refractive index because it has a lot of carbon in it and the light bounces around inside the crystal to make it look shiny.
What are the optimum conditions for crystal growth?
Warmth is the key to forming crystals. A jar's surrounding should also be warm for optimum crystal growth. Warm air temperature helps water evaporation, causing the crystals to grow more quickly. Crystals with still grow in cooler temperatures, but it will take much longer for the water to evaporate. Crystal growth requires light. Again, the crystal with eventually grow in the dark, but it will take much longer.
Light evaporates water like heat so if you put a jar of what you're using to make your crystal in the sun you should have crystals forming within a few days.
NOTE: A good technique to promote optimum 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, a good a crystal can usually be obtained just by leaving the crystal on the bottom of the beaker.
Making the Crystals on Tuesday:
-2 250 ml (or bigger) beakers
- filter funnel
-a stirring rod
-a spatula or plastic spoon
-watch-glass or paper pirate hat
1.Place 25 g of potash alum in a 250 ml beaker and add 170 ml of hot water.
2.Stir the mixture until all the crystals have dissolved.
3.Filter the solution through a filter funnel (with the filter paper inserted) into another clean beaker.
4.Cover the beaker of the solution with a watch glass and set aside. Leave it in a sheltered place and allow it to stand undisturbed overnight.
5.The first beaker and funnel can be cleaned and dried and the filter paper can be thrown out.
-2 250 ml beakers
-(left over potash alum)
-camera or smart phone
-watch-glass or paper pirate hat
-log book or diary
1. The next day when you observe the solution there should be a layer of crystals which formed as the solution cooled down.
2.Gently pour off the liquid above the crystals into the clean beaker and set aside. Make sure the crystals are left in the other beaker.
3.Using a stirring rod scrape the bottom of the glass beaker and leave the crystals to sit for another night. From all of the crystals you must choose one that you will you observe and use for your photos.
4. Using tongs or tweezers transfer the chosen crystal into the middle of the beaker with the decanted solution.
NOTE: If you want the crystal to grow quickly, suspend the crystal on a piece of string tied to a pencil resting on the edge of the beaker.
5. Take a photo of the crystal beside the ruler and mark its size. With a permanent marker measure the level of liquid in the beaker.
6.Record this information in your logbook.
7. Cover the solution with a loose fitting paper pirate hat. This allows water to slowly evaporate and keep out dust or foreign particles. Ensure your jar is kept somewhere where the temperature will stay constant.
-2 250 ml beakers
-camera or smart phone
-a log book
-tweezers or tongs
1. Record the level of liquid in the beaker and without moving the crystal take a photo with ruler beside the jar.
2. Estimate and record how much the crystal has grown.
NOTE: Avoid disturbing the crystal and don't touch it with your fingers!
3.If the crystal isn't growing anymore you can create a new solution using the previous steps and gently transfer the crystal once the solution is at room temperature. The solution may be left overnight to cool before the crystal is added.
4. Once the experiment is finished, carefully remove the crystal from the beaker, dry it with a tissue and measure its height and width with a ruler.
5. Compare the measurements to the original size of the crystal in your log book.
Tuesday Photo and Observations:
The photos above are from Tuesday. On Tuesday when I observed my crystals I noticed that there was only one large crystal and many tiny crystals. My partner and I re-did the crystal experiment because we were not satisfied with our result as there were not enough good crystals. We discovered that the crystals grew well because they were in a consistent environment until we took them home.
The crystal above is the large crystal from our first experiment that I used for my final crystal.
Wednesday Photos and Observations:
On Wednesday when I observed my crystals they were much bigger and there were not many small crystals or powders at the bottom of the beaker. The level of liquid had not changed from the day before however the crystals looked different.
Thursday Photos and Observations
On Thursday I measure my largest crystal and I measured the level of liquid in the beaker.
The level of liquid in the beaker was 3.5 cm.
NOTE: The photos with the ruler are from Thursday
On the hoildays
Over the holidays I recorded the level of solution in my jar of crystals once a week. I noticed that by the first week of the holidays the level of liquid had dropped by 1 cm. During the holidays I took many photos of my crystals so I could keep a stable track of how they were growing. On the first week of the holidays there were still many small crystals and flat icicles at the bottom of the beaker.
By the end of the second week of the holidays my crystal was 1.9 cm long and it was very hard and round in shape. The other image is of the other crystals inside my jar. They were flat, paper thin and they were easy to break in half.
Below is a table of the level of liquid in the jar and the dimensions of my crystal.
In this artwork the light that has passed through the crystal looks dull and light refracting through the medium could possibly pass through in different directions causing the light to blur.