What are non-Newtonian fluids? Examples can certainly be found even in your refrigerator, but quicksand is considered the most obvious example of a scientific miracle - fluid and solid at the same time due to suspended (suspended) particles.
About viscosity
Sir Isaac Newton argued that the viscosity, or resistance of a fluid to flow, depends on temperature. So, for example, water can turn into ice and vice versa precisely under the influence of heating or cooling elements. However, some substances that exist in the world change viscosity due to the application of force, and not to a change in temperature. Interestingly, the commonly used tomato sauce, which becomes thinner with prolonged stirring, is considered a non-Newtonian liquid. Cream, on the other hand, thickens when whipped. Temperature is not important for these substances - the viscosity of non-Newtonian fluids changes due to physical impact.
Experiment
For those who are interested in applied science or just want toto amaze your guests and friends with an incredibly simple and at the same time amazingly fascinating scientific experiment, a special recipe for a colloidal starch solution has been created. A real non-Newtonian liquid, made with literally two ordinary culinary ingredients, will amaze both schoolchildren and students with its consistency. All you need is starch and pure water, and the result is a unique substance that is both a liquid and a solid.
Recipe
- Pour about 1/4 pack of cornstarch into a clean bowl and slowly add about 1/2 cup of water. Intervene. Sometimes it is more convenient to prepare a colloidal starch solution directly with your hands.
- Continue adding starch and water in small portions until you have a honey-like consistency. This is the future non-Newtonian fluid. How to make it homogeneous if all attempts to stir evenly end in failure? Do not worry; just give the process more time. As a result, for one package of cornstarch, you will most likely need one to two glasses of water. Please note that the substance becomes more dense as you add more powder to it.
- Pour the resulting substance into a frying pan or baking dish. Look closely at its unusual consistency as the "solid" liquid pours down. Stir the substance in a circle with your index finger - slowly at first, then faster and fasterfaster until you have an amazing non-Newtonian fluid.
Experiments
Both for the purposes of scientific knowledge, and just for fun, you can try the following experiments:
- Slide your finger over the surface of the resulting clot. Did you notice anything?
- Immerse your whole hand in the mysterious substance and try to squeeze it with your fingers and pull it out of the container.
- Try rolling the substance between your palms to form a ball.
- You can even slap the clot with your palm with all your might. The spectators present will probably scatter to the side, expecting to be sprayed with a starch solution, but the unusual substance will remain in the container. (Unless, of course, you spared the starch.)
- A spectacular experiment is offered by video bloggers. For him, you will need a music column, which should be carefully covered with thick cling film in several layers. Pour the solution onto the film and turn on the music at high volume. You will be able to experience stunning visual effects only possible with this unique compound.
If you're doing an experiment in a lab in front of schoolchildren or college students, ask them why a non-Newtonian fluid behaves the way it does. Why does it seem solid when squeezed in the hand, yet flow like syrup when the fingers are unclenched? At the end of the discussion, you can pack the clot in a large plastic bag with a zipper to save it.until next time. It will be useful to you to demonstrate the properties of the suspension.
Mystery of substance
Why does a colloidal starch solution behave like a solid in some cases, and like a liquid in others? In fact, you have created a real non-Newtonian fluid - a substance that defies the law of viscosity.
Newton believed that the viscosity of a substance changes only due to an increase or decrease in temperature. For example, engine oil flows easily when heated and thickens when cooled. Strictly speaking, non-Newtonian fluids also obey this physical law, but their viscosity can also be changed by applying force or pressure. When you squeeze a colloidal clot in your hand, its density increases significantly, and (even if temporarily) it seems to turn into a solid. When you open your fist, the colloidal solution flows like a normal liquid.
Things to keep in mind
The irony is that it is impossible to mix starch with water forever, because as a result of the experiment, you do not get a homogeneous substance, but a suspension. Over time, the powder particles will separate from the water molecules and form a hard lump at the bottom of your plastic bag. It is for this reason that such a non-Newtonian liquid instantly clogs sewer pipes, if you just take it and pour it down the sink. In no case do not pour it into the drain - it is better to pack it in a bag and just throw it ingarbage chute.
