General Question

ustiegirl's avatar

Why is the tearing of paper a physical change not a chemical change?

Asked by ustiegirl (1points) November 9th, 2008

physical changes

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7 Answers

timothykinney's avatar

The chemical bonds in the paper molecules (cellulose) are not being broken, and no new materials are being formed as a by-product. Chemical change implies a change in the chemical make-up of the reagents. I.e., the breaking of some bonds and formation of other bonds. Alternatively, ionization and radical formation could be thought of as chemical change. Phase change would be a change between solid, liquid, or vapor. Tearing does not classify as any of these.

Said another way, paper is lots of cellulose fibers that have been mashed into a thin film and then allowed to dry. When you tear the paper, it is just tearing this film. The fibers themselves are not destroyed. You could take torn paper, get it warm and wet, and then make new paper from it. This is because the cellulose fibers are intact.

Another example: human beings cannot digest cellulose (e.g., grass). It passes through our digestive system as fiber. Other animals can digest cellulose (cattle, rabbits) because they have special mechanisms (multiple stomachs, intestinal bacteria) for chemically breaking the cellulose structure down into simple sugars. Simply tearing the grass into very small bits does not release the energy stored in the cellulose. To metabolize cellulose one must actually break the chemical bonds that form it.

Does this help?

amurican's avatar

Got to love it!

asmonet's avatar

I love it when people come here for homework. :-P

autumn43's avatar

And they get it done!

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