Crystals are Cool: Making Rock Candy

Wish I Had Noted the Name
Creative Commons License photo credit: biggertree

There are so many different kinds of crystals all around us, but just what are they anyway?

Put simply, a crystal is a grouping of molecules or atoms that is organized in a specific way.  Every crystal has a unique shape and properties that make it recognizable.  In today’s experiment, we will be working with sugar crystals which are oblong and slanted on the ends.

There are a couple of things going on that contribute to the growth of sugar crystals in this experiment.  First, you will be creating a supersaturated solution by heating a saturated sugar solution and allowing it to cool.

Supersaturated solutions are solutions that are so full (of sugar in this case), that they are unstable.  The solution you will create will contain more sugar (the solute) than it can hold in a liquid form.  Therefore, the sugar must come out of solution – forming what is called a precipitate (also known as yummy rock candy).  The second mechanism that helps to form the sugar crystals is evaporation.  Slowly, the water evaporates from your solution.  As this happens the solution becomes even more saturated with sugar and the sugar will continue to come out of the solution and form sugar crystals.

Blue Sugar
Creative Commons License photo credit: karsten.planz

What you are left with is a delicious science treat!  Make sure to only eat a little at a time and keep the rest sealed in a baggie.  Also, don’t forget to brush your teeth; it is pure sugar after all!  Have fun in your kitchen lab and don’t forget to be safe!  Always include an adult when trying new experiments.

Grab a handy adult; you will need one to do this activity!

Materials:
Granulated sugar – 1 cup
Water – ½ cup
Saucepan
Food coloring
Two canning jars
Spoon

What to do:
1. Dump one cup of sugar and ½ cup of water into your saucepan.  Don’t stir it!
2. Find your adult and have them help you put it onto the stove over medium-high heat.  Wait for the mixture to come to a boil and let it boil for one minute without stirring.  If you want colored rock candy, you may add some food coloring while it boils.
3. Instruct your handy adult to pour this mixture into the two canning jars.
4. Find a place on your counter that you can let the two jars sit undisturbed for two weeks.
5. Observe them once a day.  Slowly, crystals begin to form.  When you see a crust form on top of the jars, use a spoon to carefully break the crust so the water can continue to evaporate.  Don’t do anything else to your jars other than this!
6. When you feel like you have enough crystals of the right size, have an adult help you remove them from the jar using a dull table knife.
7. Eat and enjoy!  Don’t forget to brush your teeth, it is sugar after all!

Super Cool Surface Tension

winter
Creative Commons License photo credit: shioshvili

Did you know that water is sticky?  It may not look sticky, but water molecules love to stick together.  Water molecules pull and tug on each other from all directions.

Look at a glass of water. A special stretchy “skin” forms at the top of a glass of water because the molecules are pulling from the sides and from below, but not from the top.  This “skin” is known as surface tension.  Surface tension allows the water level to get higher than the walls of the glass without spilling!  Let’s put this to the test.

Materials:
Drinking glass
50-100 pennies
Paper towels

Procedure:
1. Fill a glass to the top with tap water.
2. Set your glass on a paper towel.
3. Carefully add pennies one at a time.  Be sure to keep count. 
4. Observe the water at the top of the cup.  Eventually it will begin to bulge out.
5. Add pennies until the water begins to drip over the edge of the glass.  How many pennies were you able to get into the cup?
6. Now, remove all of the pennies and get a new cup of tap water.  This time add several squirts of dishwashing liquid to the cup and try the activity again.
7. Were you able to add more pennies or did it hold less?  What do you think is happening?  Research and find out!

Sharky-Locks and the Three Gummi Bears

Need another excuse to buy candy this October?  Like cheap entertainment? Of course you do! How about some do-it-yourself grow-animals? For a buck or two, you can have a hundred edible expanding critters of your very own.

You need a few gummi bears or other gummi snacks (I grant you they are of questionable nutritional value, but they have their uses) and water. That’s pretty much it — see what we mean about cheap? 

I started with three gummi bears and one much larger gummi shark which had a disturbing layer of opaque white gummi on the bottom. 

If you want to know how much your gummi critters grow, you might want to trace around them or measure them, or just set some of your gummy snacks aside for comparison later. I had an electronic balance handy, so I used it, but that’s definitely not necessary:


The growing:  You need a container that can hold your gummi animals with a little room for expansion, and enough water to keep them covered:

And now we wait.  You may notice some expansion an hour after you begin, but your animals will look significantly bigger after 12-24 hours in water.  A few things to note: If you plan to eat your critters once they expand, please refrigerate them during the soaking process (this may slow their expansion somewhat, but you will also slow the growth of not-so-delicious bacteria). Whether you are refrigerating or not, set your critters somewhere and leave them alone as much as possible; if they jostle around too much, they may just dissolve and leave you with an unimpressive pool of colored sugar-water.

After a 20-hour soak, one of the bears intimidates his dry brother:


The “after” measurements:

This bear grew about three times as large as it was originally, and the shark about twice as large (it might have expanded further if given more time but it fell apart after being handled.)

Here’s a brief explanationof growing gummi snacks.

Extensions to try:  Soak your critters in distilled water, salt water, soda or juice, or try soaking an expanded critter in salt water.  Do some brands of bears hold up better or expand more?

(In case you were curious: Yes, you can spell it either way: gummi or gummy.)