Academic journal article Science Scope

Producing Plastic. from Milk?

Academic journal article Science Scope

Producing Plastic. from Milk?

Article excerpt

How much plastic have you handled today? Probably a great deal--a toothbrush, shampoo bottle, and peanut butter jar in the morning, perhaps a plastic bag or two, the keys on your computer and a pen. Just take a look at your car and see how much plastic it contains! In the 21st century, plastic is pervasive in our lives.

There are numerous types of plastics, most of which are derived from petroleum. Some are quite rigid and durable, including those used to make furniture, buttons, and many toys. Others, such as water bottles and food containers, are more pliable. Still other plastics can be drawn into fibers like nylon and rayon or into sheets to make wraps and bags. While there are many different types of plastics, they all have one thing in common--they are made of long chains of molecules called polymers that can be molded or shaped. In fact, the root word of plastic is from the Greek verb plassein, which means "to mold or shape" (Freinkel 2011). It is precisely for this reason that plastic is so common in our everyday lives--it can be made into a nearly unlimited number of shapes for a variety of uses.

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The Next Generation Science Standards (NGSS) requires middle-level students to "gather and make sense of information to describe that synthetic materials come from natural resources and impact society" (MSPS1-3; Achieve Inc. 2013, p. 38). PS1.B: Chemical reactions is the disciplinary core idea on which the performance expectation is based: "Substances react chemically in characteristic ways. In a chemical process, the atoms that make up the original substances are regrouped into different molecules, and these new substances have different properties from those of the reactants" (NRC 2012). In this 5E learning cycle lesson, students engage in the chemical-engineering challenge of determining the most economical way to increase the yield (the amount of plastic) of a chemical reaction. They will use milk and vinegar to produce casein, a type of plastic, and manipulate the amount of vinegar and the temperature of the milk.

This type of challenge is a major focus for many engineers who are responsible for manufacturing processes.

The engineering practice of constructing explanations and designing solutions from the NGSS states that students "undertake a design project, engaging in the design cycle, to construct and/or implement a solution that meets specific design criteria and constraints" (MS-PS1-6; Achieve Inc. 2013, p. 40). Note that while many students associate engineering with the design of objects such as cars, bridges, and computers (fewer realize that engineering is also related to the design of everyday objects such as pens and paper clips), it is less common for students to connect engineering with designing a process for making a product.

History

People have been using natural materials for millennia to make tools and other objects. Animal skins, elephant tusks, mud, clay, and many plant materials have been used. Patent books from the early 19th century, when people began to seek more durable materials, are "filled with inventions involving combinations of cork, sawdust, rubbers, and gums, even blood and milk protein, all designed to yield materials that had some of the qualities we now ascribe to plastic" (Freinkel 2011, p. 2). In 1867, the New York Times wrote of the possible extinction of elephants, since a million pounds of ivory were consumed each year, much of it to make billiard balls. A contest was held by a manufacturer of billiard balls to seek an alternative material, and in 1869, John Wesley Hyatt won the contest by discovering celluloid, which was made of cellulose from cotton and nitric acid. Celluloid billiard balls were never widely used because they, and the process to make them, were dangerous and flammable.

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Casein, a plastic made from the proteins in milk, was used by ancient Egyptians in pigments for wall paintings. …

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