1 chapter 7 chemical reactions 7.1 chemical reactions copyright © 2008 by pearson education, inc....
TRANSCRIPT
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Chapter 7 Chemical Reactions
7.1 Chemical Reactions
Copyright © 2008 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Physical Change
In a physical change,• The identity and
composition of the substance do not change.
• The state can change or the material can be torn into smaller pieces.
Copyright © 2008 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Chemical Change
In a chemical change, • Reacting
substances form new substances with different compositions and properties.
• A chemical reaction takes place.
Copyright © 2008 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Some Examples of Chemical and Physical Changes
Table 7.1
Copyright © 2008 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Classify each of the following as a
1) physical change or 2) chemical change
A. ____Burning a candle.
B. ____Ice melting on the street.
C. ____Toasting a marshmallow.
D. ____Cutting a pizza.
E. ____Polishing a silver bowl.
Learning Check
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Classify each of the following as a
1) physical change or 2) chemical change
A. 2 Burning a candle.
B. 1 Ice melting on the street.
C. 2 Toasting a marshmallow.
D. 1 Cutting a pizza.
E. 2 Polishing a silver bowl.
Solution
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Chemical Reaction
In a chemical reaction
• A chemical change produces one or more new substances.
• There is a change in the composition of one or more substances.
Copyright © 2008 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Chemical Reaction
In a chemical reaction,
• Old bonds are broken and new bonds are formed.
• Atoms in the reactants are rearranged to form one or more different substances.
• Fe and O2 form rust (Fe2O3).
Copyright © 2008 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Evidence of a Chemical Reaction
• Physical changes that can be seen are evidence of a chemical reaction.
Table 7.2
Copyright © 2008 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Learning Check
Identify the visible evidence of a chemical reaction in each of the following:
1. Methane gas in an outdoor heater burns with a blue flame.
2. Bleach removes stains from a shirt.
3. Bubbles of CO2 are released when baking soda is mixed with vinegar.
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Solution
Identify the visible evidence of a chemical reaction in each of the following:
1. Methane gas in an outdoor heater burns with a blue flame. Heat and a flame
2. Bleach removes stains from a shirt. Color change (color removed)
3. Bubbles of CO2 are released when baking soda is mixed with vinegar. Formation of a gas (bubbles)