Get ready to watch some cool crystals grow and when you're done, you can eat them!
What You Need:
- 1 1/2 cups of white sugar
- 3/4 cup of water
- A spoon
- Small saucepan
- Tall glass or jar
- Piece of clean kitchen twine
- A pencil
- An adult to help you
What You Do:
- Pour the water into the saucepan and ask an adult to help you heat it on the stove until it boils. Don't turn the stove off yet.
- Pour the sugar into the water and stir until no more of the sugar will dissolve (you will still be able to see little grains of sugar floating around at the bottom of the pan). If all of the sugar dissolves at first, add a little more until you can't get any more to dissolve when you stir it. This is called a saturated solution. It means that the solution can't hold any more sugar.
- Keep cooking the liquid and stirring it until it is clear, but not for more than 5 minutes, or it will get too hot and turn into hard candy! Turn off the stove when it starts to look clear.
- Have an adult pour the sugar water into the glass, but go slowly to make sure that none of the undissolved sugar from the bottom of the pan goes into the glass. Fill the glass about 2/3 full. (You might have enough for two glasses.)
- 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!
- Carefully move your glass to a place where it won't be accidentally bumped. Check it each day to watch the crystals grow. Within a few days, you should start to see a few crystals growing on the string. After about one week, you will probably have a lot of crystals on your string. When your piece of "rock candy" is as big as you want it to be, take it out of the glass and hang it in a clean glass to dry. Then you can take the pencil off, cut the extra string off, and enjoy eating your sugar crystals off the string!
Optional: To make your rock candy more colorful, try adding 1-2 drops of food coloring to your sugar solution before putting the string in.
In step two you made a saturated solution -- there was so much sugar in the water that the water didn't have room to dissolve any more, so some was left in the bottom of the pan. When you dipped the string into the solution in step five, some of the dissolved sugar stuck to the string. Once the saturated solution started to cool, the loose sugar molecules in it (called the solute) started to join with the sugar molecules on the string. Then, the water molecules (called the solvent) started to evaporate or dry up into the air, leaving sugar molecules behind. Those molecules gradually joined with the sugar molecules on the string and became 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 can grow crystal snowflakes from a chemical called Borax and use them as pretty winter decorations!
What You Need:
- Wide-mouth jar
- 3 pipe cleaners
- A pencil
- 1-cup measuring cup
- Food coloring (optional)
- Glow-in-the-dark paint (optional)
- Ribbon (optional)
What You Do:
- Twist the three pipe cleaners together in the middle of each section to form a 6-pointed star shape.
- Tie a piece of string to one end of the star. Connect the string to the next point by twisting it around the pipe cleaner. Continue around until you connect all the points together with the string, making a snowflake skeleton (see the picture).
- Tie another piece of string to one of the pipe cleaner points and tie the other end around the pencil. Place the snowflake in the jar with the pencil resting across the mouth of the jar. Make sure that the snowflake hangs without touching any part of the jar. Take the snowflake out of the jar.
- Use a teakettle or microwave to boil enough water to fill the jar. Have an adult help you add the hot water to the jar. As you do, measure out how many cups of water are needed to fill the jar. For every cup of water placed in the jar, mix in three tablespoons of borax. This will make a saturated borax solution. Stir the borax solution with a spoon until as much of it dissolves as is possible.
- Hang your snowflake in the jar so that it is completely covered in the solution. Let it sit overnight. Gently remove your now crystal-covered snowflake in the morning and let it dry by hanging it in a dry jar.
Optional: To make colored snowflakes, use colored pipe cleaners and add 1-2 drops of food coloring in step four. To make your snowflakes glow in the dark, paint the pipe cleaner snowflake with glow-in-the-dark paint in step two and let it dry completely before going on to step three. Tie a ribbon to one point of your snowflake to make a Christmas tree ornament!
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 snowflake), you gave the solution the right conditions to grow crystals! Once the crystals started to grow on your snowflake 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 early, cold mornings. To learn more about snow and ice crystals, check out our Snow and Hail article.
Salt vs. Sugar
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!
What You Need:
- A teaspoon of table salt
- A teaspoon of white granulated sugar
- Two sheets of black construction paper
- A magnifying glass
- Crystals worksheet
What You Do:
- Put a teaspoon of salt on one sheet of black paper and a teaspoon of sugar on the other.
- Use your fingers to spread the grains apart a little so you can see them better. Now look closely at the grains on each sheet of paper and compare how they look. Do you notice any differences between the two?
- Now use your magnifying glass to look up close at a few grains of the salt. What shape are they? Are they all about the same shape? Draw their shape in the correct spot on the worksheet.
- Now take a look up close at a few grains of the sugar. What shape are they? Are they a different shape from the salt crystals? Do you notice anything else that makes them look different from the salt? Draw their shape on the worksheet.
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? Highlight after this sentence for the answer: it's Sugar!