Get in the Halloween mood with some slime! Today, we’re going to make slime with potato starch… aka SPUD MUD!
First, what exactly is starch? There are all sorts of important nutrients in our diet. Think about what humans need to survive. Make a list.
Carbohydrates are a crucial source of energy in the human diet and are most readily used when our body is active. One carbohydrate that we get from many of our foods is starch.
Starch is a carbohydrate found in a variety of plants and grain products, such as potatoes, pasta, or rice. Starch is stored within the plant as an energy source, and is one of the most common carbohydrates in the human diet.
One thing that we use pure starch for is to thicken foods. If you try to mix starch with water or other cold ingredients, it will eventually settle to the bottom. If starch is heated, the molecules swell, and the tiny grains of starch absorb water. Once that water is trapped in the starch molecules, the food thickens. When the food is removed from heat, it will thicken even more as it cools. For more on how starch thickens foods, click here to check out our last blog and make some pudding! This time, we aren't going to heat our starch, we're going to use it to make a non-Newtonian fluid.
That brings us to our project: we're going to make our own spud mud! If you've ever made "Oobleck," then you know what it's like! This time, you’re going to try out potato starch instead of the commonly used cornstarch.
This weird slimy substance that you’re going to be working with today is a non-Newtonian fluid. Non-Newtonian fluids behave very differently from normal liquids or solids. Instead, they sometimes behave like a liquid and sometimes behave like a solid. When you apply pressure to a non-Newtonian fluid, it resists and behaves like a solid. As soon as you release the pressure, the fluid returns to liquid form.
To make this type of non-Newtonian slime, you need two basic ingredients: starch and water. Typically, cornstarch is used to make this kind of slime, but any type of starch will work. What about something else that contains starch, like flour?
Test this out: Compare potato starch to flour.
Scoop 1/2 cup of potato starch into one cup and half a cup of flour into a second cup. Mix 1/2 cup of water with each and stir. What happens?
Add a few drops of food color if you would like. If your spud mud is too runny, add a little more starch. If it’s crumbly, add more water. A little goes a long way!
Next, we're going to try to extract our own starch from potatoes! Your job is to determine which potatoes have the most starch. This project requires some wait time,
so after you complete the first part of your project, you can continue to get messy with your spud mud!
YOU WILL NEED:
* Food processor or knife
* Large bowl
* Stove or microwave
* 3 Jars or clear bowls
Here's what to do!
1. Choose your first potato variety.
2. Wash the potatoes off well to remove any dirt.
3. Put two-three potatoes (of the same variety) in the food processor and process until they are in small chunks. You will need enough for two cups of chopped potato.
5. Heat four cups of water over the stove.
6. Pour hot water over the potato chunks (just enough to cover them) and stir for 3 minutes. Notice that the water starts to change color as you stir!
9. Over the next 10 minutes, check back every 2 minutes and write down any observations.
10. Repeat the process with the other two potato varieties. Make sure you use the same amounts of potato pieces, water, and jar size so results are comparable!
11. As you check back, you should see that the water has begun to separate. You might see a layer of water on the top or a layer of white on the bottom. The white layer is your starch!
Below, the sweet potato formed a starch layer on the bottom within minutes.
13. Compare your results. Do you see any big differences? Does one potato obviously have more starch on the bottom than the other? Did your results match your predictions?
More starchy experiments:
Make your own gravy and test foods for starch: www.discoveryexpresskids.com/blog/science-of-starch
Compare gelatin and starch in two chocolate pudding recipes:
Get in the fall mood with some pumpkin slime: https://www.discoveryexpresskids.com/blog/fall-fun-make-your-own-pumpkin-slime