Growing Alum Cystals
By Kimberley Scanlon
Plan : Tuesday
- potash alum - funnel
- hot water - filter paper
- 2 X clean beaker
1. Dry all your utensils. Put approx 25g of potash alum in a beaker that is bigger than 250ml. Add 170 ml of hot water. Stir until all crystals are dissolved. the mixture may be cloudy or milky.
2. Using another beaker with filter paper on it, filter the warm mixture into the beaker.
3. Cover the beaker of the mixture 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 filter paper can be thrown out.
4. Take a photo
- clean beaker
1. Observe the beaker and the solution inside it, the bottom should be covered in a layer of crystals that have formed while the solution was cooling down.
2. Be careful and take care as you pour off the clear solution above the crystals into another clean beaker and then set this aside for later. Make sure you leave the crystals that are left behind in another beaker.
3. If no crystals have formed overnight, the solution can be “seeded” by adding another crystal from the original alum.
4. Let your crystal now stand overnight again and observe the formation the next day by taking a photo
5. Take a photo
- clean beaker
1. Using a spatula transfer a group of crystals into the centre of a beaker, that contains the decanted solution.
2. Tie a piece of string to a pencil and place it above the jar, the string should just be above the crystal.
3. If possible, take a picture of the crystal next to a rule so you can interpret the size of the crystal. Mark the level of water in the beaker and record a date in your diary.
4. Cover the mixture with a loose bit of paper so it can keep the dust out while allowing the water to slowly evaporate.
5. To keep the mixture's temperature as constant as possible, keep it away from direct sunlight and heaters or air conditioners.
6. Take a photo
Observations : Tuesday
The beaker with the alum and hot water appeared to be very cloudy and milky. When we filtered the hot water into the other beaker, it appeared to be very clear and it looked like water. The water was very still as well.
Our first beaker that we grew the crystals in to separate into different beakers had changed over night greatly! It wasn't really a layer of crystals at the bottom, it was more many different scattered crystals at the bottom. The crystals were quite large and covered mostly the bottom of the jar. The water was still quite clear inside, but on the side of the jar there were many little droplets of water.
By now, we had separated the crystal solution and crystals into our own beaker. We didn't end up doing the string method because the crystals were already growing in the bottom. Overnight, more solid large crystals had formed at the bottom of the jar but it wasn't as much as we had started with because it was separated. The sides still had water droplets and the crystals were all sorts of different shapes.
What is a crystal?
Crystals are solids that are formed by regular repeated patterns of molecules connecting together.It is formed from an ordered arrangement of atoms, moleculs or ions. Because there are repeated units, crystals have recognisable structures. In some solids, the arrangements of atoms and molecules can be random or very different throughout the material. Each crystal has diifferent properties and shapes. For example, sugar crystals ar eoblong and slanted at the ends and salt crystals are cubic. There are seven systems of crystal structures, which are also called lattices or space lattices. Crystals
What substances can be used to make crystals?
There are many common substances and chemicals that can be made to make crystals. The main chemical for growing crystals is Aluminium Potassium Sulfate. Another common chemical is Ammonium Chloride. You can also use Epsom salt which is another name for the chemical magnesium sulfate. The key to growing crystals is to make a supersaturated solution of water and salt or sugar. Water is the solvent and salt or sugar is the solute.
What are some examples of crystals in nature? What household items can you also grow crystals from?
Many crystals have formed by magnetic and metamorphic processes. Rocks such as granite which have cooled very slowly and under high temperatures have completely crystallized. The other crystalline rocks are marbles, mica-schists and quartzites. There are also mineral crystals (gem stones), stalactites and stalagmites and snowflakes. Water-based ice is in the form of snow and sea ice and glacier are very common examples of crystals in nature. Also, crystals can form when liquid rock, called magma cools. If it cools slowly, thenc rystals may form. Many valuable crystals such as diamonds, rubies and emeralds form this way. A single snowflake is typically a single crystal. Salt is also a common example of a crystal. You can also use household items to grow crystals. When at home, mostly you start with a saturated solution. You can items such as sugar, salt, alum and hot water to make this solution.
Explain the process of crystal growth.
Crystal Growth is a major stage of the crystallization process and consists in the addition of new atoms or ions into the arrangement of a Bravais Lattice. This growth normally follows an initial stage of nucleation. The process of nucleation and growth generally occurs in two different stages and generally quite slow because the initial crystal components must have an effect on each other in the correct direction and placement for them to form the crystal. In the first stage, a very small nucleus containing a newly formed crystal is created. After crystal nucleation, the second stage is the growth section. The crystal growth spreads outwards from the place of nucleation which then continues to grow.
In another explanation, the process of crystal forming is called crystallization. Crystals often form in nature when liquids cool and start to harden. Certain molecules in this liquid gather together as they attempt to become stable. This happens in a repeating pattern which then forms the 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 again to create a certain shape. A crystal grows by adding atoms or molecules to all its sides in the exact same pattern as they were added before. Each of the different crystals are made up of a different building block therefore they each have a different structure or shape. Also, factors that go into the formation of crystals like temperature, pressure and chemical conditions lead to different shapes too. eg. Salt crystals are square in shape and Epsom salt crystals are long and rectangular.
Outline a few different types of crystals.
Some different types of crystals are: Agate, Amber, Amethyst, Quartz, Bornite, Calcite, Emerald, Fluorite, Jade, Opal, Ruby and Sapphire.
There are few different ways to outline different types of crystals. Many times crystals are grouped by their lattice types or what crystal system they are part it. Some other people also group them according to their physical properties. ed. Covalent crystals, Metallic crystals, Ionic crystals and Molecular crystals. The seven different crystal systems are:
- TRICLINIC: not symmetrical from one side to the other, often strange shapes.
- MONOCLINIC: skewed tetragonal crystals, often are prisms and double pyramids
- ORTHORHOMBIC: like tetragonal crystals except not square in cross section, often rhombic prisms or look like two pyramids that are stuck together.
- TETRAGONAL: similar to cubic crystals but no they are longer alone one axis instead of the 6 axis of the hexagon.
- TRIGONAL: these posses a single 3 fold axis of rotation instead of the 6 fold axis of the hexagon.
- HEXAGONAL: these are six sided prisms. When you look at the crystal from one end, the cross section is a hexagon.
- CUBIC:these are generally cube shapes but are not always cube shapes. This part also contains octahedrons (8 faces) and dodecahedrons (10 faces).
What effect do crystals have on light travelling through them? (relate to reflection, refraction, dispersion and diffraction)
A Crystal normally has a higher refractive index meaning that the light inside them is bent and travels slower than travelling in the air. Total Internal reflection often occurs as a result of their higher refractive index. Total Internal Reflection happens when a beam of light travelling through a dense medium crosses the interface with a rarer medium. For example, from glass to air. Many crystals at jewellery shops at mounted on reflective surfaces to make them appear more brighter and appealing to your eyes. Crystals can also be cut at a specific angle to make sure that there is the max amount of total internal reflection. Sometimes the light exiting the crystal is refracted so much that dispersion happens. When you are looking at a crystal and you see a small spec of colour inside of it, this is dispersion.
What are the optimum conditions for crystal growth?
Warmth is the key to forming crystals, therefore the jar's surroundings should be warm for optimum crystal growth. Warm air temperature helps the water evaporate which cause the crystals to grow more quickly. Crystals are capable of growing in cooler temperature but it will take much longer for the water to evaporate. Crystal Growth also requires light. The crystals will eventualyl grow in the dark but it will take longer. If the crystals are places in the light, it will evaporate the water as heat does. If you place your crystal jar in a sunny spot with warmth and light then it should grow fast.
Materials Safety Data Sheet
1st Week - Wednesday
On Thursday in the first week of the holidays I took a few pictures and looked at my crystal. The water height was at 2 cm and was under the sun in a warm spot. The water had not evaporated on the sides yet and was the same height as when I started. The size of the crystals in the jar were still small, about .5 of one cm. However about 1 crystal was 1 cm in diameter. The water still seemed very clear and there were no little droplets on the side of the jar. I wouldn't say more crystals had formed since I last looked at it. Maybe just a few more small crystals have formed since last time. They haven't grown much. Overall, not much has changed since last time.
2nd Week - Tuesday
This week the water level had gone down quite a lot. The solution level was now at 1.5 cm, so it had dropped .5 of a cm. Much more crystals were forming at the bottom of the beaker and hardening and taking different shape. The crystals were getting bigger and now most of them were about one cm in diameter and some were two cm too! The sides of me jar was now fogging up with lots of water droplets on the side, meaning the water was finally evaporating! The side of my jar was very very foggy,cloudy and patchy with lots and lots of small water droplets on the inside.
Overall, I think my crystals grew alright. My biggest crystal is 2.5 cm in length and my smallest crystal is 1 cm in length. I just had several different sized crystals, not one big and large crystal. They are all very ragged and sharp looking but every crystal has different properties. If you touch it, it's actually quite a smooth feeling.
TABLE OF SOLUTION LEVELS TABLE OF CRYSTAL SIZES
Last Week of School : 2.5 cm Last Week of school: 0.4 cm
1st Week of Holidays: 2 cm. 1st Week of Holidays: 0.5 cm
2nd Week of Holidays: 1.5 cm 2nd Week of Holidays: 1 cm & 2 cm
Final Liquid Height: 1.4 cm Final Crystal Size: 2.5 cm
how does the artwork demonstrate the properties of the crystal?
In many ways, when you grow crystal its known as an artwork. The properties of a crystal can range from harsh and sharp to smooth and lovely. These crystals demonstrate the beauty of crystals and are all sorts of different shapes. They are kind of harsh and not smooth but they are beautiful because they grew in their free form, following the flow.
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