By Pancho J. Villamoran
So you and your friends, after a long day go to a restaurant to socialize, destress and chill. They ordered a bucket of fries. The fries – delicious. But what could make it more delicious? Add ketchup, of course. It comes in a bottle. Now, how do you pour a fair amount of ketchup to the amount of fries you have?
It’s not like a water as it flows – like a drain. It doesn’t respond to force linearly like oil and many alcohols like if you push twice as hard on a container filled with oil, it they move twice as fast. These kinds of fluids are called Newtonian fluids. Yes, from the man who made apples famous: Sir Isaac Newton. Ketchup is from the merry band of rule breakers, such as mayonnaise, toothpaste, peanut butter, blood, and paint, Non-Newtonian Fluids, whose apparent thicknesses changes depending on how hard you push, how long, or how fast. The resistance to flow arises because of the friction that is created when layers and particles bump into each other, thus making them “slide” over each other. If there was no difference between the speeds of each layer, there would be no resistance then.
Ketchup is non-Newtonian because they harder you push, the thinner it gets. It’s not like quicksand the non-Newtonian liquid Oobleck, made of water and corn starch, because rather than getting thinner, applying greater forces makes it thicker and more in solid-state.
Below its normal state and pushing force, ketchup acts as a solid because it is basically made of crushed tomatoes, formerly solid. Once applying force to it and going over the breaking point, it goes a thousand times thinner than it is before. This would shower your fries in a pool of ketchup.
But if you apply a force significantly below the threshold, it all depends on time. The container, moving side to side, may cause the ketchup particles to crowd to the middle, and the consistency of the ketchup’s fluid, usually made up of water, vinegar, corn syrup, and some other spices, may act as a lubricant in order for it to flow. Or another theory states that the particles may clump with each other to make small groups that would slide past each other. Yes it will flow, but scientists are still unsure how to explain how. People propose the best way to pour out ketchup from its bottle is to give the bottle a few hard shakes still with its cap on, “waking up” the particles, and pour to our heart’s content.
Scientists are still actively researching about the physical properties of ketchup because on a Physics perspective, ketchup is one of the more complex liquids out there. Its viscosity is unique compared to other common liquids. Ketchup remains one of the greatest and tastiest condiments known to man, and an interesting physics topic for researchers and scientists over the world.