by Diane Cretin
I love science. It was my favorite subject in school. This week I decided to do a science experiment that parents or grandparents could do with children. Or you can be a big kid and just do it for yourself.
I found this experiment in this book The Chemistry of Cola: Discover and Learn With 21 Experiments by Dr. Jamie Gallagher, which I bought through Usborne books. I thought all of the experiments were going to involve cola but actually many of them do not. The experiments are really about different aspects of chemistry.
This experiment walks you through how to make a density rainbow. The question is asked: Can water float on...water? The answer is yes if you make the water denser by mixing it with other ingredients. In this experiment you create a rainbow of sugar water by mixing different densities of sugar solution.
You will need:
Tall glass
Food coloring (ideally five colors, but at least one)
Granulated sugar
Water
5 small glasses
Spoon to use for stirring
Measuring spoons
Paper towel
Kitchen scale - optional in case you prefer to measure the sugar in grams
What to do:
Add 3 tbsp. of tap water to each of your five small glasses and add a few drops of food coloring to each. If you only have one color, add it only to glasses one, three, and five. If you have five colors, add a different color to each glass.
Don't add any sugar to glass one, but add 1 1/5 tablespoon (15 gm) of sugar to glass two, 2 2/3 tbsp. (30 gm) to glass three, 3 1/2 tbsp. (45 gm) to glass four, and 4 2/3 tbsp. (60 gm) to glass five. My note: the sugar was obviously originally measured in grams, so you will have to do your best to estimate some of the partial tbsp. measurements.
Stir the glasses with the sugar. Your should find that the sugar in glasses two and three dissolves quickly while the sugar in four and five takes longer to dissolve. If after several minutes of stirring there is still solid sugar remaining in glasses four or five, heat the glasses (if using glass, not plastic) in a microwave for short bursts (ten seconds at a time) to slightly warm the water. Sugar water will warm rapidly and can burn your skin, so be careful to make sure you do not splash it on your skin. Ask an adult for help.
When you have dissolved as much sugar in glass five as possible, add it to the bottom of the tall glass.
Cut a strip of paper towel approximately 1 inch wide and 4 inches long. Dip one end in glass four and then place the wet towel against the inside of the glass; it should stick there.
Use the paper towel in glass four to guide the liquid gently into the tall glass by pouring the liquid slowly down the paper towel and into the glass, rather than pouring straight from one glass into another. The liquid from glass four should be less dense than the solution from glass five and should therefore float on top.
Repeat steps five and six with glasses three, two, and one (in that order).
What Happens?
Because you created different densities of water by adding varying amounts of sugar, you should be able to float different concentrations of sugar water on top of each other. You should end up with a glass filled with different colors and densities.
How This Played Out for Us in Real Life
I found out I needed to go to the grocery store because someone put the food coloring away with an empty red bottle of food coloring. Olivia had Sunday School to take part in, so I filled the cups with water before heading to the store. I had previously bought two different sizes of plastic glasses at the grocery store to see if one worked better than the other and set them up on the table. I measured the water and added it to each cup. Then I added the food coloring.
By the time I got back from the store, Olivia was working on her room as she got a new (to her) loft bed and other furniture. So this delayed our experiment. I planned to do it after my 4:00 zoom literature group from church. At 3:45 Olivia was desperate to do the experiment. So I went downstairs and talked her through adding the sugar to each glass.
Then I had Olivia get Grandpa Lee to see if he would help her do the rest of the experiment while I took part in my zoom call. He graciously said yes.
Here is what it looks like using the paper towel strips:
Lee said the experiment did not work 100% well, especially using the plastic glasses. He got the best results when he transferred liquid to a small glass made of glass. I think that was due to the diameter of the glass, not because of what it was made of. Also, since I did the cleanup, I know the sugar was not completely dissolved in all of the glasses. You want to make sure you do that to get the best results.
This is what the book says your result should look like:
Here are a few pictures Lee took as I texted him during my zoom asking him to take some pictures.
I want to do this experiment again with Olivia using three food colors. Since food coloring comes in four colors, you have to mix two to get a fifth color and it can turn out very dark. That way we could add food coloring to glasses one, three, and five, but leave two and four without food coloring so you could see a nice clear layer between colors. You do obviously need to add sugar to all five glasses.
I hope you have fun doing this experiment.
Continued blessings,
Diane