Cornstarch is an example of a polymer. Polymers are long strains of molecules that keep repeating and have different properties of the original single molecule group. A single section of a polymer is called a monomer. It resembles the simplest form of the repeating portion of the entire polymer. These polymers may get stretched when you make a mixture such as cornstarch and water. This mixture behaves a certain way. There are many theories on why this may occur. One theory is because the strands get tangled, making it hard for them to slide against each other. Stretched molecules would offer more resistance to movement, like the resistance of a stretched rubber band. However, this argument does explain why rapid motion (stirring, shaking, etc.) increases viscosity, which is the property of a fluid that offers resistance to flow.
Cornstarch and water is a non-Newtonian, organic fluid. Fluids can fall under different sub groups. They are either Non-Newtonian or Newtonian. They can also be either organic or non organic. NonNewtonian Fluids are a group of liquids that change viscosity when they are stirred, shaken, or otherwise agitated. Cornstarch and water acts differently depending on whether it is still or agitated. This kind of fluid is called a dilatant. It becomes more viscous (has a relatively high resistance to flow) when agitated or compressed. The viscosity of a non-Newtonian fluid is also dependant on temperature. Cornstarch would decrease in viscosity if put in a boiling pot (it would become thinner). Examples of Newtonian fluids include motor oils, mineral oils, gasoline, kerosene, and most salt solutions in water.
The most popular explanation for the behavior of cornstarch and water is that when sitting still, the tiny grains of starch are surrounded by water. The surface tension of the water keeps it from completely flowing out of the spaces between the grains. The lubrication of water allows the granules to move freely. However, if the movement is abrupt (shaking, stirring, poking, slapping, etc.) the water is squeezed out from between the granules and the friction between them increases dramatically.
Other examples of polymers are present in our everyday lives. Water-resistant paints and varnishes derive from a family of synthetic polymers called acrylics. Polystyrene foam, or styrafoam, is used when making cartons to protect eggs, or making packing peanuts to cushion fragile objects for shipping. It insulates, so people put drinks in foam cups and coolers to keep the warm ones warm and the cold ones cold. Placed behind walls and ceilings in homes, polystyrene foam keeps the weather outside. Polyethylene is the plastic used to make two liter soda bottles. Polyethylene is melted, inserted into molds, and blown up like balloons to make containers for soft drinks, fruit juices, water, and milk. Polyvinyl chloride, (PVC), Is better known as vinyl. Easy to clean, waterproof, and resistant to corrosion, vinyl is used in car interiors, siding for homes, and in sewage pipes. The plastic nylon replaced the silk in hosiery in 1938. Many of the airborne troops in World War II floated to earth beneath nylon parachutes. Other synthetic fibers such as polyester made the fashions of the 1970s possible.
Polymers can also be found everywhere in nature. With turtles and tortoises, plates made of bone and encased in hornboth constructed of polymersform the turtle’s tough shell. People once used the hawksbill turtle’s shell to make hair combs and eyeglass frames. Now that these turtles are endangered, most “tortoise shell” is made from a plastic polymer substitute. Similarly, antelope, buffalo, sheep, cattle, and rhinoceroses all have horns. These horns are made of the polymer keratin. Keratin is what makes up hair and fingernails, and our outer layer of skin. Fossilized tree sap made of resin polymers can becomes amber. Ancient Greeks called amber “electron” because of its ability to give an electrical shock. This gave electrons and electricity their names. Cow’s milk is full of the polymer casein. Without this polymer, cheese would not be solid. The Chinese discovered that they could unravel silk, a polymer, from the silkworms’ cocoons and weave it into soft fabrics. From trees in the rainforest comes a milky white fluid polymer called latex. This can form a solid that is elastic. If you rub it on words made with pencil, the words would disappear, so it was called rubber.
The last place polymers are found are in recycling. Polystyrene can be made into plastic drinking cups and CD cases. It can also be foamed, converting it into the compressible material used in foam cups, coolers, and packaging peanuts. Recycled polystyrene can be made into concrete and insulation. PETE, or PET, is used to make containers for soft drinks, salad dressing, mouthwash, and peanut butter. Drinks won’t leak through it, and neither will the gas that makes soda fizzy. PETE can be recycled into new bottles and containers, carpet, backpacks, clothing, and many other products. Most plastic bags are made from LDPE. It gets recycled into things such as trash bags, trash cans, and compost bins. Recycled HDPE appears in everything from pens and drainage pipes to park benches and doghouses.
In conclusion, polymers are all around us. They affect our everyday lives and our in many of the products we use. Cornstarch and water is just one fun experiment used to demonstrate the uniqueness that is a polymer.