## Chemistry 9th Edition

Published by Cengage Learning

# Chapter 1 - Chemical Foundations - Additional Exercises: 96

#### Answer

a) Cutting food - $Physical$ $change$ b) Interaction of food with saliva and digestive enzymes - $Chemical$ $change$ c) Proteins being broken down into amino acids - $Chemical$ $change$ d) Complex sugars being broken down into simple sugars - $Chemical$ $change$ e) Making maple syrup by heating maple sap to remove water through evaporation - $Physical$ $change$ f) DNA unwinding - $Physical$ $change$

#### Work Step by Step

Reasons: a) Cutting food does not form any new substances, and thus is a physical change. b) Food is broken down when saliva and digestive enzymes react with it, forming new substances. Thus, it is a chemical change c) Proteins form new substances called amino acids, and thus this is a chemical change. d) A new product (simple sugar) is formed from a complex sugar, and thus this is a chemical change. e) Only water is evaporated, which condenses back easily and turns back into a liquid form, which can be once again mixed with the maple sap. This is a physical change as no new substances are made. f) DNA unwinding is a physical process, as one DNA strand only splits into two, forming no new substances. Thus DNA unwinding is a physical change.

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