Will Quicksand Kill You? The Science Of Goo: Cornstarch, Quicksand, Oobleck, And Non-Newtonian Fluids
The Dangers Of Quicksand
Many people have seen a movie or television show in which a person becomes trapped in quicksand. They will be walking along and step in the wrong place and will then be sucked into the mucky goo, often without chance of escape. Quicksand is an interesting material. It can act as a solid or a liquid. It is this combination that makes quicksand so tricky. The great thing about quicksand is that it is very easy to reproduce at home. It is made out of very inexpensive materials and only takes a few minutes to create. We are going to mix up some homemade quicksand, do a number of different activities, and explore the science behind this notorious, quixotic liquid.
What Is Quicksand Made Of?
Quicksand is a soupy fluid made up of sand or earth and often water. It forms when something causes sand, earth, or clay to have reduced friction and fluid-like properties. Typically this something is water. The water in quicksand separates the individual particles and reduces the friction. Quicksand is often in wet areas such as near riverbeds, swamps, or marshes. The water may come from nearby bodies of water or may be trickling up from an underground spring. Sometimes quicksand can form without any water. An earthquake can shift the ground in such a way that reduces the friction between grains of dirt or sand.
Can Quicksand Really Kill People?
Quicksand can kill people; however, it typically doesn't kill people by drowning them. Humans are actually less dense than quicksand. Humans may sink up to their waists, but will go no further. The problem is that quicksand traps people. Motion will loosen the grains of sand and reduce the friction. The fast, panicked motion of a person trying to escape quicksand is what actually sucks a person deeper in the quicksand. (Watch the Magic Sand Puzzle Solution to the right. This puzzle is much like an experiment that researchers did to learn more about quicksand.) Once the quicksand settles again, it will act more like a solid. This can make it very exhausting to try to work oneself out of the muck. If you get too exhausted from trying to escape, you may die from exhaustion and exposure.
Below, you will find a video from the Discovery Channel. It features Bear Grylls explaining and demonstrating how to escape from quicksand.
Homemade Cornstarch Quicksand (Oobleck)
Quicksand is a non-Newtonian fluid. Its viscosity changes based on how much force is being applied and at what speed the force is being applied. This is why quicksand can be difficult to escape. Most of us will never have the opportunity to experience quicksand. Fortunately, cornstarch in water, commonly known as oobleck, has very similar properties to actual quicksand. Both oobleck and quicksand change viscosities based on the amount of stress that is being applied to the substance. At times they act like a solid and at other times they act like a liquid. Oobleck and quicksand have another similarity, they both can trap people. (Watch the video to the right to see someone become trapped in oobleck.) We are going to mix up some cornstarch quicksand and do some simple activities so that you can understand some of the unique properties of quicksand and other non-Newtonian liquids.
Cornstarch Quicksand Cautions:
- Do not pour this liquid down the drain. It will clog your pipes in inexplicable ways.
- Be prepared for silliness, fun, and a big mess.
- Cornstarch Quicksand is fairly easy to clean up, but there is a good chance that you will get it everywhere.
- Cover the area in which you plan to experiment, work, and play so that clean up is quick and easy.
- 1 box (16 oz.) Cornstarch
- Large mixing bowl
- Cookie sheet or baking pan
- Pitcher of water
- Newspapers or drop cloths
- Small plastic toy or figurine that won't be damaged by being submerged
- Pour around 1/4 of the box of cornstarch (around 4 oz.) into the bowl.
- Slowly mix in around 1/2 cup of water using a spoon or your hands.
- Add water until the mixture is around the consistency of honey. If it is too thin, add more cornstarch. If it is too thick, add some additional water.
- Play with the cornstarch quicksand. Pay attention to how it behaves when it is mixed up. Once it is fully mixed, try some of the activities below.
More Things To Try
Cornstarch Quicksand (Oobleck) Activities
- Stick your hand slowly into the bowl of oobleck quicksand. How does it feel? What happens if you try to swirl your hand around quickly in the mixture?
- Try rolling the mixture into a ball. What happens? With your palm towards the ceiling, open up your hand and see what happens to your ball.
- Drop your animal or toy into the cornstarch quicksand. Can you rescue it from the oobleck? How do you think this relates to escaping from real quicksand?
- Pour some of the mixture onto the pan. How does it pour?
- Try smacking your hand onto the oobleck puddle. What happens?
- Scrape the puddle up using your fingernails and see how it behaves.
Watch the videos to the right to get some additional ideas for things to try out. Cornstarch Quicksand (Oobleck) is a really neat substance. If you try anything that isn't mentioned here, leave notes in the comments so that someone else can try it.
If you are feeling daring and have a very large amount of cornstarch, try filling up a tub or small baby pool with Cornstarch Quicksand. You can try running across it, sitting in it, or escaping from it.
Critical Thinking Questions
- What did you notice about the consistency of the Cornstarch Quicksand (Oobleck) mixture?
- What happened to the toy that you dropped into the mixture? Was it easy to remove? Using what your learned from this activity, describe what you think it might feel like if you ended up in some quicksand. How would you recommend escaping from quicksand?
- Can you think of any other substances that behave in a similar fashion to the Cornstarch Quicksand? How are they similar or different from each other?
- Is the quicksand similar to other liquids (water, honey, glue)? How is it the same or different?
- This substance is called a non-Newtonian fluid. Why do you think it has that name?
- Read the information below on non-Newtonian fluids. Why is it important to know that quicksand is a non-Newtonian fluid?
For More Fun
- Make Homemade Silly Putty & And Enjoy A Non-Newtonian Fluid
Silly Putty, another non-Newtonian fluid. Try this easy recipe that uses white glue and liquid starch. This activity includes an easy recipe, experiments to try, and critical thinking questions.
Cornstarch Quicksand (Oobleck) and real quicksand are both non-Newtonian Fluids. This means that how they behave changes based on how much stress is being applied. Non-Newtonian fluids change viscosity when the amount of applied stress changes. When there is a lot of stress, many non-Newtonian fluids will become very viscous and resemble a solid. When a non-Newtonian fluid is under very little stress it will often have low viscosity and act more like a fluid. This is why you can roll the Cornstarch Quicksand into a ball, but when you release the ball, it appears to melt. This is also why it can be difficult to escape from real quicksand; the faster you move, the more the quicksand will act like a solid.