Chemistry experiments can be a fun, colorful, and enlightening way to learn about the chemistry of the world around you. Everything is made of chemicals, after all – the word “chemical” doesn’t just refer to “artificial” substances. Chemistry is involved in our food and nutrition, in the products we use to clean our homes, in the living processes in our cells, and much more. Here are a few fun and interesting experiments to try that are based on chemistry.
BLACK LIGHT PATROL
What things glow under a black light? You can buy hand-held black lights for under $20 at novelty stores or through the internet. Turn out the lights and go on a black light hunt. You’ll find that many of your clothes glow. Why? Go shine the light in the detergent box and you’ll find out why the detergent makes “whites whiter and brights brighter!” Some minerals and semiprecious stones fluoresce (such as fluorite), so if someone has a mineral collection or a collection of stone bead jewelry, see if any of the stones fluoresce. You may find some surprises, too. That spot on the rug that’s glowing? Isn’t that where Spot had an accident? Yes, the substances that give urine and feces their characteristic color also fluoresce as they break down.
Here’s some chemistry to help you clean up. You’ll need some citric acid, which can sometimes be purchased at stores that sell candy-making supplies, and fragrance oils which can be purchased at craft stores. Mix about two tablespoons of citric acid, two tablespoons of corn starch, and 1/4 cup of baking soda in a jar. Add a few drops of any fragrance oil that you like. Add a few drops of food coloring if you want. Put a lid on the jar and shake well until the oil and coloring are mixed thoroughly with the dry ingredients. Pour the dry mixture into a bowl and slowly drizzle 3 tablespoons of good vegetable oil into it. Olive oil is fine, but almond, avocado, coconut, or similar oils will add their own fragrance. Stir well until all of the oil is mixed into the dry ingredients. Shape into balls about 1 to 1 1/2 inches across, or press into large candy molds. Let dry 24 to 48 hours, and store in a sealed container. When you add a fizzy to water, the chemical reaction between the baking soda and the citric acid produces bubbles of carbon dioxide gas – the fizz!
VITAMIN C TEST
This simple test uses iodine, which can be found at most pharmacies. When mixed with starch, iodine turns blue-black. Vitamin C, if present in sufficient concentration, breaks up the starch-iodine complex. Mix about 1/4 teaspoon of corn starch with 1/4 cup of boiling water and stir well, until the starch is dissolved. Add one or two drops of iodine, enough to turn the mixture bluish-black. Divide the mixture into several small cups. To each cup, add any substance that you want to test for Vitamin C: orange juice, other fruit juices, etc. You can blend dry foods, such as cereal or cooked rice, with some water to add to your starch-iodine mixture. Crush a Vitamin C tablet and mix with water to see how much Vitamin C is needed to change the color of the starch-iodine mixture. Be sure to wash out or throw away any containers that have touched the iodine, and don’t eat anything that has iodine added to it.
Iodine can also be used to test foods to see if they contain starch. Take a small sample of the food and place it on a disposable plate. Drop a small amount of iodine on the food. If the iodine turns blue-black, the food contains starch. Try different foods and keep track of your results. Be sure to throw the samples away when you are finished.
This little experiment demonstrates the density of carbon dioxide gas. You’ll need an aquarium or other large container (an ice chest would work). Half-fill a glass with vinegar and add a spoonful of baking soda. The solution will fizz as it produces carbon dioxide gas. Set the glass in the aquarium until it stops fizzing. Light a match and lower it into the aquarium. Where it goes out indicates the carbon dioxide level. Continue generating carbon dioxide until the tank is filled. Take a bottle of bubble solution and make a bubble by waving the bubble wand in the air, so that the bubble is filled with atmospheric air. Use the wand to direct the bubble into the aquarium. It will gently fall, but will float on top of the carbon dioxide layer because carbon dioxide is more dense than the mixture of gases that makes up atmospheric air. Try blowing bubbles with your breath, which has more carbon dioxide than air. Do the bubbles still float?
CLEAN PENNIES AND COPPERY NAILS
Take 20 or so dull pennies and put them in a glass container. Add about 1/4 cup of white vinegar. Nothing will happen to the pennies, but when you add a teaspoon of salt and stir, the pennies will soon brighten. The sodium chloride (salt) interacts with the acetic acid (vinegar) to produce a weak solution of hydrochloric acid, which dissolves the copper oxides that make the penny dull. Now remove the pennies and put an iron nail (not galvanized or aluminum) in the solution so it’s half in and half out of the solution. Leave it there for about 10 minutes as you observe for signs of a reaction. After 10 minutes, remove the nail. The acidic solution dissolves some of the iron from the nail and exchanges it for the copper in the solution, depositing the copper on the nail. You may also see bubbles of hydrogen gas caused by the interaction between the acid and the iron.
MAKE A GEODE
Geodes are geological features formed by basic chemistry. Wherever there is a small hole in an igneous rock – the kind of rock produced by cooling lava – a geode can form. Water seeps into the space, carrying dissolved minerals. The minerals accumulate and form crystals over time. The crystals may become semi-precious stones such as agate or amethyst. You can make your own “geodes” from eggshells. Carefully crack an egg in half. Use the insides for cooking. Wash the shell out and carefully remove the membrane. Several household chemicals will make great crystals. Try salt, baking soda, borax, washing soda, alum, or cream of tartar. Pour about 1/4 cup of boiling water in a jar, and add as much of the chemical you have chosen as you can dissolve in the water. Add a little food coloring if you like. Pour the solution into the shell. You can rest the shell in an empty egg carton. Let the solution slowly evaporate. The slower it evaporates, the larger the crystals will be.