So just what are Crystals?
First we need to talk a little bit about exactly what makes up everything in the universe. You may have heard about atoms. If not, atoms are tiny building blocks that make up physical things that exist in the universe. Everything that we can see and touch is made up of atoms; right from the air around us which we can’t even see, but can feel to the moon and even something as big as the sun. Atoms can join with other atoms and make more complex things called molecules. An example of this is water. Each molecule of water is made of 1 Oxygen atom and 2 Hydrogen atoms. Both Oxygen and Hydrogen are gasses, but when they join together the properties of the resulting molecule make it a liquid (at room temperature).
Now some atoms or molecules have special properties that make them stack very neatly when a bunch of them join together. The salt that you put on your food is a crystal.
This is what a a salt crystal would look like if you could see it up close. One of the coolest things about crystals is how they form. Basically, they grow! One molecule only needs to come into contact with another one and they start organising themselves based on their properties. Table salt is a good example because as you can see the molecules stack themselves nice and neatly in blocks.
So lets grow some crystals!
Preparation – What you will need:
- A glass or jar
- A toothpick or a pencil
- A paperclip
- Boil some water and pour it into your glass or jar
- Stir in 2 to 3 table spoons of salt until all of the salt dissolves
- Keep adding more salt and stirring it in until the salt won’t dissolve any more
- Cut a strand of cotton that is just long enough to tie around your toothpick or pencil and then reach the bottom of the glass or jar when you rest the toothpick or pencil over the opening
- Wet the cotton in your mixture and then tie one end to the pencil or toothpick
- Tie the other end to the paperclip
- Rest the pencil or toothpick across the opening of the glass or jar and lower the cotton and paperclip into the water
Unfortunately this experiment really takes time because you need to wait for the water to evaporate. So make sure you put the jar in a sunny spot where it won’t be bumped at all like a windowsill and make sure to check back on it every day to watch the progress. When the water has completely dried up you should be left with a bunch of salt crystals on the piece of cotton that was dangling in the water.
If you did it right you should end up with something like this:
But why did it do that??
When the water starts evaporating, it leaves behind the salt that was dissolved in it. And the easiest thing for the salt to do is stick to other salt molecules. To make them grow nicely in one place we need what is called a “seed” – basically a molecule (or many molecules) that stays in one place. That’s where our cotton string comes in. Some of the salt in the water sticks to the cotton and then the salt in the water sticks to those molecules on the cotton strand. If we didn’t do this you just end up with a big lump of salt at the bottom of the jar and it wouldn’t be very interesting at all.
Other things to try:
There are other household crystals that you can do the same trick with. The obvious one is sugar. So you can use sugar in the water too if you have a sweet tooth. Try adding some food colouring to water as well. You can end up with some funky looking green salt to put on your potatoes at dinner!
Other every day examples of crystals:
There are very many crystals that are always around in our daily lives without even knowing it. Your mom’s diamonds that are in her rings or earrings are crystals. If you didn’t already know, diamonds are among the hardest things that exist. Almost nothing other than another diamond can cut a diamond! And did you know that diamonds are made of the same stuff that your dad makes a braai with?! It’s an atom called Carbon. And carbon can arrange itself into many different crystal structures – one of those structures is called a diamond.
Crystals are also used in watches to keep time. If you pass electricity through crystals they vibrate. Scientists learned how to measure those vibrations very closely. They found one crystal called Quartz which vibrates exactly 60 times every second. And so we use quarts crystals in watches to help us measure the time.