A crystal is a solid material with atoms and molecules that are arranged in a consistent repeating pattern, creating one of seven geometrical shapes. Crystals can be expensive and beautiful, like amethysts or diamonds, but they can also be found right in your kitchen in the form of sugar and salt! You can easily grow crystals by adding a crystal-forming chemical to water and waiting for the water to cool or evaporate.
Growing crystals can take several days, but this super-easy recipe gives you a cup full of needle-like crystals in just a few hours!
Epsom salt is another name for the chemical magnesium sulfate. The temperature of the water determines how much magnesium sulfate it can hold; it will dissolve more when it is hotter. Cooling the solution rapidly encourages fast crystal growth, since there is less room for the dissolved salt in the cooler, denser solution. As the solution cools, the magnesium sulfate atoms run into each other and join together in a crystal structure. Crystals grown this way will be small, thin, and numerous. To grow large single crystals, you'll need to follow the evaporation procedure in the next project.
Crystal Growing Experiment Kit
Grow crystals you can eat! This unique crystal kit uses pure sucrose and "seeded" crystal growing sticks to make large, beautiful rock candy crystals in just one week. The kit comes with one pound of pure sucrose for clear crystals. The rock candy can form in just seven days! You provide adult supervision, a saucepan, and water.
You can grow single, large crystals that look like gems by using a seed crystal. Here's how to do it:
The small crystals that formed in the saucer grew because of nucleation. A few alum molecules found each other in the solution and joined together in a crystal pattern. Other alum molecules continued to join them until enough molecules gathered to become a visible crystalline solid. (Chemists call that a crystal "falling out of" the solution.) If you left these crystals in the solution they would continue to grow, but they wouldn't get very big because they would all be competing for the remaining alum molecules in the solution. Instead, you took one crystal and used it as the only nucleation site in the solution. It was the primary site for the alum molecules to join together, so the crystal could grow quite large!
There are many factors that affect crystal growth, so crystal projects are great for scientific experimentation and science fairs. For example, many crystals are formed because of evaporation. Temperature and humidity are two things that affect the rate of evaporation, so you could design an experiment to see how different temperatures and humidity levels affect the rate of crystal growth and the size of crystals. Another aspect to test is the rate at which your solution is cooled: if you make a solution with boiling water, will crystals grow better if it's allowed to come to room temperature slowly or if it's cooled in the refrigerator?
There are many substances that can be used to grow crystals. You could design an experiment to test which one grows larger crystals under the same conditions. Try alum, Epsom salt, table salt, sugar, baking soda, or non-household chemicals like copper sulfate (blue crystals) and potassium ferricyanide (red crystals) - adult supervision is required for the last two.
Get ready to watch some cool crystals grow! And when you're done, you can eat them or give them away as Christmas gifts!
Note: You can make Rock Candy without the sticks as well. Use a piece of clean cotton string or thread. Follow steps 2-7 below then dip the string into the solution so that half of the string is coated. Take the string out and let it dry. Once the string has dried, tie the clean end around a pencil and put the dipped end back into the glass of sugar water solution, balancing the pencil across the rim of the glass. Make sure the string does not touch the bottom or the sides of the glass, or your crystals will not form right! When your piece of "rock candy" is as big as you want it to be (about one week), take it out of the glass, let it dry, and enjoy!
In step two you made a saturated solution -- there was so much sugar in the water that it couldn’t dissolve any more sugar and some was left in the bottom of the pan. Once the saturated solution started to heat up, the water was able to dissolve even more sugar and a supersaturated solution was formed in step three. Then, as the solution cooled, the sugar molecules in it started to join with the sugar molecules on the sticks. The sugar on the sticks are called “seed” molecules and the sugar molecules in the solution attached themselves to the seed molecules. Meanwhile, the water in the solution started to evaporate or dry up into the air, leaving only sugar molecules behind. More sugar molecules gradually joined with the ones already on the stick, forming larger crystals. Because all of the solute molecules are the same (they are all sugar), they all form the same shape of crystals and they all stick together, making a big chunk of sugar crystals that are pretty to look at and tasty to eat!
Note that this is a special science project that is safe to eat because you only used food products, not any chemicals, and you used clean dishes from your kitchen. Never eat any experiment unless it is made entirely out of food and you only used clean dishes to prepare it!
In this project, you use a chemical called borax to grow crystals shaped like snowflakes, stars, or candy canes. Then you can use them as pretty decorations!
What You Need:
Just like in the rock candy project, you made a saturated solution of borax, which is a chemical that forms crystals when the conditions are right. By mixing it with hot water and letting it cool and having something for the borax (solute) molecules to attach to (the pipe cleaner shape), you gave the solution the right conditions to grow crystals! Once the crystals started to grow on your shape, more and more crystals formed around them. Ice crystals that real snowflakes are made of are not quite like these borax crystals, but they do look sort of similar and they both are pretty and sparkle when light shines on them. Real ice crystals are made only of water. The difference is that they are formed when water vapor in clouds freezes and falls to the ground as snowflakes! Frost is another form of ice crystals that you might see on windows and grass on cold mornings. To learn more about snow and ice crystals, check out our Snow and Hail article.
How can you tell the difference between sugar and salt? They're both crystals and they look very similar - they are both small, white-colored grains. Of course if you tasted each of them, you would know right away which one was salt and which was sugar because they taste very different. In this project you will find out how to tell sugar and salt apart just by looking at them!
Sugar and salt grains are actually tiny crystals. If you were to make a saturated solution of each of them, you would be able to see them grow into much larger crystals, but they would always have the same shape as these tiny crystals do! The salt crystals are cube shaped (like dice) and have six sides. The sugar crystals are very rough looking and are shaped more like rectangles with pointed ends. Most of the crystals are the same shape and size and look very similar to each other, but you probably saw a few crystals on your paper that looked a little different. Those crystals probably had pieces broken off of them, or there might even be more than one crystal stuck together, making them look different from the others. Also, the coloring of the crystals is a little different. Sugar crystals look very clear and sparkly while salt is duller and looks more white-colored or frosted.
Can you tell if the picture above is of salt or sugar? It's Sugar!
You have probably seen lots of crystals, but just what are they and how do they form? Grow some crystals of your own to find out more about these fascinating and beautiful wonders!
What Are Crystals?
A crystal is a hard, solid substance made of molecules that bond together in specific patterns to form an interesting shape that has straight edges and flat surfaces. Not all crystals have the same shape, as you saw in the salt vs. sugar project - there are actually lots of different kinds of crystals, and each kind has its own special shape. Some crystals that you are probably very familiar with are sugar, salt, and ice. But many other solids are made of crystals too; we just can't see them because they are so small! Lots of minerals form beautiful crystals that are used for jewelry, like diamonds or emeralds. Crystals are often transparent, which means that you can see through them sort of like you can see through glass. Other kinds have beautiful colors.
What Are They Made Of?
What a crystal is made of actually depends on what kind of crystal it is -- for example, salt, sugar, and snowflakes are actually formed out of different kinds of crystals! Snowflakes are made from crystals formed by frozen water. (You can see a picture here.) Salt crystals are formed by some chemical elements -- sodium and chlorine -- which join together in a crystal shape. (You can see a picture of salt crystals here.) Sugar crystals and rock crystals are made up of different chemical elements, too.
Crystals can be formed in several different ways. Most crystals are formed through evaporation. For example, when water from saltwater evaporates (or is dried up into the air), salt crystals are left behind (do the Borax Snowflakes project to see this happen). Ice crystals are formed when water from the Earth evaporates into the air and becomes a gas called water vapor. The water vapor becomes clouds and then freezes and falls back down to earth as snow. Ice crystals can also form as frost on windows and on the ground when the air has a lot of moisture (water vapor) and the temperature is below freezing. Some types of crystals are formed from melted rock in the earth (remember this from when we talked about Volcanoes?). When the hot rock cools gradually, it will sometimes form crystals. Geodes are round rocks that are formed when bubbles are trapped in the melted rock. As the bubbles cool down, crystals grow inside of the bubble of rock!
As a crystal grows, the pattern that makes it a certain shape will be repeated over and over, so the crystal will always keep the same shape as it gets bigger! The chemical elements that a crystal is made of are what tell the crystal what shape it will be. A crystal of salt is a different shape than a crystal of sugar (do the Salt vs. Sugar project to see for yourself!) because they are both formed from different elements. A lot of crystals might seem to look alike at first glance, but what elements the crystal is made out of will make it a unique shape and color. Even the same element can make different crystals, though, based on conditions such as temperature and light and what other elements are around. For example, the graphite used inside of pencils is a kind of crystal made from the element carbon, which is actually the same element that diamonds are formed from!
Ways Crystals Are Used
Use this worksheet along with the Salt vs. Sugar project to let kids (especially early elementary students) draw their results from the project! The other half of the page will help them review which things are made of crystals and which are not.