AbstractHave you ever wondered how fun toys like Silly Putty®, Gak™, and Slime™ are made? These products are so much fun because of the properties of polymers, which make them delightfully bouncy, stretchy, sticky, moldable, breakable, hard, soft, and just plain fun! In this science project you can be the developer of your own slime product by changing the amount of a key ingredient. By observing the physical properties of your results, you can choose the best recipe for your new product.
Thanks to the members of the Science Education Council at PPG Industries, for testing, feedback, and advice on this science project. Read more about how PPG's scientists partner with Science Buddies to make great activities.
Determine the best recipe for your own homemade slime by changing the amount of a key ingredient and by observing physical properties.
If you have ever played with slime, you know that it can be fun with all of its stretchy, bouncy, ickiness. Maybe you have noticed that some types of slime feel different than others. Have you ever wondered why slime behaves the way it does? It all has to do with chemistry. Chemistry is the study of matter, which is the stuff that everything around you is made of. Chemists are interested in finding out what different materials, such as slime, are made of, how these materials behave, and how they can be changed into other materials.
What is slime actually made of? If you have made slime before, you probably followed a recipe to put different ingredients together, similar to baking a cake. The ingredients used for slime usually include Elmer's® glue and borax. Elmer's glue is made up of a polymer. Polymers are long chain-shaped molecules.
The polymer chains in the Elmer's glue are long and very straight. The polymer chains can slide across each other easily, making the glue runny and "liquidy" (think of dumping a bunch of fresh-cooked spaghetti out of a pot). This changes, however, when you mix the glue with borax. The borax helps make connections between each of the polymer chains, as shown in Figure 1. This process is called crosslinking. This makes it harder for the polymer chains to slide around, making the glue thicker and turning it into "slime."
Figure 1. Straight polymer chains (left) are linked together by borax to form a cross-linked polymer (right).
In this project, you will use contact lens solution to make slime. It contains other ingredients (boric acid and sodium borate) that react with baking soda (another ingredient in your slime) to make borax. You might wonder if it matters how much borax you add to the glue. Changing the recipe can change the properties of the slime! In science, a property is something about a material that you can observe and measure, for example its weight, color, or stickiness. In this science project, you will make slime with different amounts of contact lens solution. You will then test the slime and observe how its properties change as the recipe changes. Once you have tested all your slime recipes, you can decide for yourself which one results in slime that will be the most fun to play with. If you were going to sell slime as a toy, which recipe would you use?
Terms and Concepts
BibliographyLearn about the history and chemistry of Silly Putty on this webpage:
- Pop-Cult.com. (n.d.). Silly Putty. Retrieved August 27, 2013.
- Polymer Science Learning Center. (2003). Making Things Out of Polymers. University of Southern Mississippi. Retrieved December 13, 2005.
- Rader, Andrew. (2005). Matter is the Stuff Around You. Rader's Chem4Kids. Retrieved December 13, 2005.
For help creating graphs, try this website:
- National Center for Education Statistics, (n.d.). Create a Graph. Retrieved June 25, 2020.
Materials and Equipment
- Washable PVA school glue (like Elmer's®)
- Baking soda
- Contact lens solution (must contain both boric acid and sodium borate in ingredients)
- Food coloring (optional)
- Measuring spoons
- Measuring cups
- Mixing bowl
- Kitchen countertop or other work surface that can get messy
- Resealable plastic bags or food storage containers
- Lab notebook
Preparing Your Slime
- In the mixing bowl, thoroughly mix 1/2 C water, 1/2 C glue, and a few drops of food coloring.
- Add 1/2 tsp baking soda and mix completely.
- Add 1 tbsp contact lens solution and stir vigorously until the mixture starts pulling away from the edges of the bowl.
- Use your hands to knead the slime (fold it, squeeze it, and roll it) for 5–10 minutes until its texture stops changing.
- Put the slime in a resealable plastic bag or food storage container. Use a marker to label the bag "1 tbsp contact lens solution."
- Clean any residual slime off your mixing bowl and measuring spoons/cups. You should be able to peel the slime off in pieces.
- Repeat steps 1–6 two more times, first using 2 tbsp and then 3 tbsp of contact lens solution. When you are done, you should have three batches of slime, as shown in Figure 2.
Figure 2. Three batches of slime made with 1, 2, and 3 tbsp of contact lens solution.
Testing Your Slime
- Prepare a data table like Table 1 in your lab notebook.
|Circle diameter after 1 minute (cm)|
|Amount of contact lens solution||Slime description||Trial 1||Trial 2||Trial 3||Average|
- Take your first batch of slime (with 1 tbsp contact lens solution) and play with it with your hands. What does it feel like? Is it stretchy? Squishy? Sticky? Rubbery? Write down your description of the slime in your data table. This is a qualitative observation (it uses things you can describe with your senses, not numbers).
- Measure 1 tbsp of your first batch of slime. Since it does not behave like a regular liquid, you will need to mold and squish the slime into the measuring spoon in order to get approximately one tablespoon.
- Roll the 1 tbsp of slime into a ball.
- Place the ball of slime onto a flat, smooth surface, and immediately start your stopwatch.
- After exactly one minute, measure the diameter (width) of the ball of slime in centimeters (cm) using a ruler (see Figure 3). Write this number down under Trial 1 in your data table. This is a quantitative observation (it uses a number that you measure).
Figure 3. Measuring the diameter of the ball of slime with a ruler.
- Repeat steps 4–6 two more times for this batch of slime, for a total of three trials. Record your measurements in the data table under Trial 2 and Trial 3, respectively.
- Repeat steps 2–7 for your other two batches of slime.
- Calculate the average circle diameter for each batch of slime. Do this by adding up the diameters for each trial and then dividing by three. Record the average diameter for each batch of slime in the data table. Ask an adult if you need help.
- Make a graph with the amount of contact solution on the horizontal axis and the average circle diameter on the vertical axis. You can use the Create a Graph website if you need help making a graph.
- Based on your results, which slime was the runniest (spread out to make the biggest circle)? Which slime was the thickest (spread out to make the smallest circle)? How do these quantitative measurements relate to your qualitative observations?
- Based on all your observations and measurements, which slime do you think is the "best"? If you were going to sell your slime as a toy, which recipe would you use? Why?
- Store your slime in airtight containers if you want to play with it later. Dispose of any excess slime by putting it in the trash. Do not pour your slime down the drain or it will cause a clog.
Ask an Expert
- Experiment with the other ingredients in your slime recipe. What happens if you change the amount of water, glue, or baking soda?
- There are many other ingredients you can add to your slime to change its appearance or other properties. For example:
- Glitter to make sparkly slime
- Iron filings to make magnetic slime
- Glow-in-the-dark paint to make glow-in-the-dark slime
- Heat-sensitive pigment to make color-changing slime
- There are other tests you can do to measure the properties of your slime. Here are a few ideas—can you think of more?
- Measure density: what is the mass of a certain volume of the slime?
- Roll 1 tbsp of slime into a ball. Pinch it with two fingers and let it drop down. Measure how long it takes to stretch a certain distance, or how far it stretches in a certain amount of time.
- Roll the slime into a ball, drop it, and measure how high it bounces. This may be easier if you use a camera to film the slime bouncing and then analyze the video afterwards.
- Compare what happens if you stretch the slime quickly vs. slowly.
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