Objectives
The ninth grade integrated science curriculum spends an entire quarter of the year exploring polymers, including plastics, petroleum, petroleum products, and other carbon applications. This unit will be used to teach most of the topics in the second quarter of the year. The appendix at the end of this unit contains the relevant New Haven standards. As New Haven's science curriculum is based on the Connecticut state science curriculum, which is ultimately based on the national standards, many teachers will find a similar place for this unit in their curriculum.
This unit will cover the entire life cycle of an ordinary plastic bottle. Most ordinary plastic water bottles are made from polyethylene terephthalate, or PET plastic. PET bottles are normally marked with a number 1 inside the three arrow recycling symbol. Polyethylene terephthalate is also sometimes abbreviated as PETE in some older publications. I have chosen to explore PET bottles for two primary reasons. My students are all pregnant and parenting teenagers, who learn the regular curriculum while they are with us. PET bottles are a familiar part of their lives because they have been told to drink lots of water while they are pregnant. Many choose to bring water in these plastic bottles from home, so the bottles are a common site around the school. Additionally, PET, as a plastic, offers an excellent opportunity to explore the diverse topics we are expected to cover while maintaining continuity throughout the term.
The unit will follow the stages of the bottle's life cycle, modeled on the typical life cycle that one might see for a living organism. Each section of the curriculum contains a bit of background about the particular stage in the bottle's life cycle, some ideas for teaching the stage and most will contain a specific suggested classroom activity.
The unit will begin with an introduction, which is designed to show the students generally where we are going with the unit. The family history section will come next as a way to introduce students to the concept that humans have existed for thousands of years without plastic water bottles. This concept is important for my students as most of my students were born after the mass consumption of single serving plastic water bottles began. These first two sections are not really part of the life cycle of the bottle as they are not repeated in a recycling story, but they help to set the stage for the life cycle stages that follow. The conceptions phase of this unit is about the bottle design. The design of an object has a large impact on how easily the object may be reused or recycled at the end of its life, so this phase is really the beginning of the life cycle, as it largely determines the eventual fate of the bottle. The section on the birth of the bottle discusses how the chemicals that make up a bottle came to be and come together. Adolescence in a bottle, like in a human is the time when the character of the bottle is formed, in this case the physical processes that are used to transform the amorphous PET flakes or pellets into the bottle itself. Adulthood, and the working life of the bottle, follows, after which, seniority ensues. The discussion about seniority will focus on how bottles can be reused and if they really should be reused. Finally, death, and for the bottle, the possibility of an afterlife (or recycling if you like) are discussed, which brings back the ideas of the importance of design and possible alternatives, which were discussed at the very beginning of the unit.
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