What is crystallization? Crystallization is a solid-liquid separation technique. An impure solid compound is completely dissolved in hot water. This solution contains the desired compound as well as impurities that float around. As the solution cools, the solute molecules start to leave the solution and form solid crystal. Each solute molecule interacts with the growing crystal; if the geometry of the solute fits with the crystal, it will hold on to the crystal better. Slower cooling produces fine, pure crystals.
Borax Crystal Ornaments
Borax, sodium tetraborate, is a natural mineral and common household product.
- Add nine tablespoons of 20 Mule Team Borax to a one quart container and dissolve in three cups of hot water. Add color to the solution using food coloring. Make sure the mouth of the container is small enough that a craft stick or pencil can balance on it.
- Using scissors, cut some pipe cleaners and bend the pieces into any shape you want. To make a six-pointed snowflake, twist together three four-inch pieces. Leave a little bit of pipe cleaner to make a loop.
- Cut a long piece of wire and thread one end through the pipe cleaner. Wrap the rest around a craft stick.
- Submerge the pipe cleaner into the borax solution and rest the craft stick on the mouth of the container. Make sure the pipe cleaner is not touching the sides or the bottom of the container.
- Cover setup with a coffee filter or parafilm to keep away dust. Let it sit overnight in a safe place where it can’t get bumped, and in the morning you’ll have a perfect ornament!
Benzoic Acid Snow Globe
Benzoic acid can be irritating to the skin and mucous membranes. If ingested in large quantities, it can be toxic. Wear gloves and eye protection while working with benzoic acid in this project.
- Add one gram of benzoic acid into 75 ml of water (five tablespoons). Heat the solution to dissolve the benzoic acid. You do notneed to boil the water.
- Glue your desired decoration onto the lid of a jar using forceps or tweezers. If you do not plan on inverting the jar, you can place the decoration at the bottom of the jar as well.
- Until this point, the benzoic acid solution should be cooling, and as it approaches room temperature, it will precipitate out of the solution to form snow-like crystals. When the benzoic acid is room temperature, pour the solution into the jar.
- Fill the jar as much as possible with water. The air pockets created will allow the benzoic acid to form clumps.
- Put the lid on the jar and seal it. Gently shake the jar, and you will see snow!
Experimenting with Polymers A polymer is a long repeating chain of smaller units. In a biological sense, proteins are polymers of amino acids, glucose is a polymer of sugars and lipids are polymers of fatty acids. These are examples of natural polymers because they can be extracted from nature. Synthetic polymers are engineered from petroleum oil; synthetic rubber is a synthetic polymer made from repeated smaller units such as isoprenes.
In this experiment, the glue is the polymer. Slime is a non-Newtonian fluid, meaning it is neither a true liquid nor a true solid. You can pick it up as if it is a solid, but when you put it back into the bowl it will spread out and take the shape of the bowl.
- Mix two bottles of Elmer’s school glue — clear, white or glittery — into one cup of liquid starch.
- Add any decorations (glitter, confetti, small toys), scents or colors that you would like.
- Let the slime sit for about 10 minutes so it loses its stickiness. Now it’s ready to play with!
You can also use two cups glue with one-and-a-half cups warm water mixed with three-quarters cup borax and one-and-a-third cups warm water. Freeze before and after play for an icy feel!
What are the properties of solids and liquids? Solids retain a fixed volume and shape and do not compress easily. Molecules in a solid do not flow easily because they are rigidly held in place. On the other hand, liquids assume the shape of the container they are placed in and flow fairly easily. These properties are because the molecules can slide past one another easier more easily. However, like solids, they are not compressible.
Holiday Air Freshener
The liquid gelatin solidifies as it cools because the properties of the solution change with decreasing temperature. The smell from the air freshener is from tiny molecules of the vapor coming off of the liquid or solid interacting with receptors in your nose.
- Mix one cup of hot water with four tablespoons of unflavored gelatin. Stir until completely dissolved.
- Add to this solution one cup of distilled water and two tablespoons of salt. Stir until completely dissolved.
- Add desired scents, oils and food coloring to solution. To make a peppermint air freshener, add peppermint extract.
- Pour liquid into jar and decorate the outside of the jar.
- Place the jar into the fridge and wait four to six hours for the liquid to solidify.
A version of this story appeared in the Thursday, Dec. 3 print edition of the Daily Nexus.