• The Chapter 7 Homework is due on Thursday, October 29 at 11:59 pm.

• The Chapter 6 and 7 Test is on Friday, October 30

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• Please get out your Chapter 6 Review Worksheet

Chapter 7Oxidation and Reduction

Energy transfers

Overview: Life Is Work

• Living cells require energy from outside sources.

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Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work.

Figure 7.2

Lightenergy

ECOSYSTEM

Photosynthesisin chloroplasts

CO2 H2OCellular respiration

in mitochondria

Organicmolecules O2

ATP ATP powersmost cellular work

Heatenergy

Electronegativity

Redox Reactions: Oxidation and Reduction

• The transfer of electrons during chemical reactions releases energy stored in organic molecules. This released energy is ultimately used to synthesize ATP.

• Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions.

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Oxidation• In oxidation, a substance loses electrons, or is

oxidized.

Reduction• In reduction, a substance gains electrons, or is

reduced (the amount of positive charge is reduced).

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Figure 7.UN02

becomes oxidized

becomes reduced

• The electron donor is called the reducing agent. (X)

• The electron acceptor is called the oxidizing agent. (Y)

• The electron donor is called the reducing agent. _____

• The electron acceptor is called the oxidizing agent. _____

becomes oxidized(loses electron)

becomes reduced(gains electron)

(Na)

(Cl)

Methane(reducing

agent)

Oxygen(oxidizing

agent)

Carbon dioxide Water

becomes reduced

Reactants Products

becomes reduced

becomes oxidized

Some redox reactions do not transfer electrons but change the electron sharing in covalent bonds.