What is a non-Newtonian fluid? Examples and experiments

What are non-Newtonian fluids? Examples can certainly be found even in your refrigerator, but the most obvious example of a scientific miracle is quicksand - fluid and solid at the same time due to suspended (suspended) particles.

On the viscosity

Sir Isaac Newton argued that the viscosity, or fluid resistance to flow, depends on temperature. So, for example, water can turn into ice and vice versa under the influence of heating or cooling elements. However, some of the substances existing in the world change the viscosity due to the use of force, rather than changes in temperature. Interestingly, non-Newtonian fluids include the commonly used tomato sauce, which becomes liquefied with prolonged stirring. Cream, on the contrary, thickens when whipped. These substances are not important temperature - the viscosity of non-Newtonian fluids varies due to physical effects.

Experiment

For those who are interested in applied science or simply want to impress their guests and friends with an incredibly simple and, at the same time, terrific fascinating scientific experiment, a special recipe for colloidal starch solution has been created. A real non-Newtonian liquid made with its own hands, literally from two ordinary culinary ingredients, will amaze students and students with its consistency. You will need only starch and clean water, and as a result you will get a unique substance that is both a liquid and a solid.

Recipe

• Sprinkle about a quarter of the cornstarch pack in a clean bowl and slowly pour in about half a cup of water. Stir. Sometimes it is more convenient to prepare a colloidal starch solution directly with hands.
• Continue adding starch and water in small portions until you have a substance that resembles honey in a consistency. This is a future non-Newtonian fluid. How to make it homogeneous if all attempts at uniform mixing end in failure? Do not worry; Just give the process more time. As a result, one box of cornstarch will most likely take you from one to two glasses of water. Note: the substance acquires a greater density as you add more powder to it.
• Pour the resulting substance into a frying pan or baking dish. Look closely at its unusual consistency, while the "solid" liquid pours down. Mix the substance around the circle with your index finger - at first slowly, then faster and faster until you get an amazing non-Newtonian fluid.

Experiences

As for the purposes of scientific knowledge, and just for fun, you can try the following experiments:

• Slide your finger along the surface of the resulting clot. Have you noticed anything?
• Immerse the entire hand in a mysterious substance and try to squeeze it with your fingers and pull it out of the container.
• Try rolling the substance in the palms to make a ball.
• You can even slap the palm with the whole force. Attending spectators will surely scatter to the sides, expecting that they are now sprinkled with starch solution, but the unusual substance will remain in the container. (If, of course, you did not regret starch.)
• Spectacular experiment offers videoblogers. For him you will need a musical column, which should be carefully covered with a dense food film in several layers. Pour the solution onto the tape and turn on the music at a high volume. You will be able to observe the stunning visual effects possible only with the application of this unique composition.

If you are conducting an experiment in the laboratory in front of students or students, ask them why the non-Newtonian fluid behaves in this way. For what reason does it seem like a solid body, if you squeeze it in your hand, but it flows like a syrup if you unclench your fingers? At the end of the discussion, you can pack a clot in a large plastic bag with a zipper to save it until the next time. It will come in handy for demonstrating the properties of the suspension.

Mystery of substance

Why, in some cases, does the colloidal starch solution behave as a solid body, and in others as a liquid? In fact, you created a real non-Newtonian fluid - a substance that rejects the law of viscosity.

Newton believed that the viscosity of a substance changes only because of an increase or decrease in temperature. For example, engine oil flows easily when heated and acquires a special density 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 colloid clot in your hand, its density increases substantially, and (even temporarily) it seems to turn into a solid body. When you unclench your fist, the colloidal fluid flows like a normal liquid.

What you need to keep in mind

The irony is that it's impossible to mix starch with water forever, because as a result of the experiment, you get a non-homogeneous substance, and a suspension. Over time, the powder particles will peel off from the water molecules and gather in a hard lump on the bottom of your plastic bag. It is for this reason that a similar non-Newtonian fluid instantly clogs the sewer pipes, if you just take it and pour it into the sink. In no case do not pour it into the drain - better pack it in a bag and just throw it into the garbage chute.