slide 1 of 20 chemistry 25.3. © copyright pearson prentice hall slide 2 of 20 fission and fusion of...

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Chemistry 25.3

© Copyright Pearson Prentice Hall

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Fission and Fusion of Atomic Nuclei

The sun is not actually burning. If the energy given off by the sun were the product of a combustion reaction, the sun would have burned out approximately 2000 years after it was formed, long before today. You will learn how energy is produced in the sun.

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Fission and Fusion of Atomic Nuclei >

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Nuclear Fission

Nuclear Fission

What happens in a nuclear chain reaction?

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Fission and Fusion of Atomic Nuclei > Nuclear Fission

When the nuclei of certain isotopes are bombarded with neutrons, they undergo fission, the splitting of a nucleus into smaller fragments.

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In a chain reaction, some of the neutrons produced react with other fissionable atoms, producing more neutrons which react with still more fissionable atoms.

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Nuclear Fission

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Fission and Fusion of Atomic Nuclei > Nuclear Fission25.3

A Nuclear Power Plant

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Neutron Moderation

Neutron moderation is a process that slows down neutrons so the reactor fuel (uranium-235 or plutonium-239) captures them to continue the chain reaction.

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Neutron Absorption

Neutron absorption is a process that decreases the number of slow-moving neutrons. Control rods, made of a material such a cadmium, are used to absorb neutrons.

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Animation 30

Take a close look at a nuclear fission chain reaction.



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Nuclear Waste

Nuclear Waste

Why are spent fuel rods from a nuclear reaction stored in water?

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Fission and Fusion of Atomic Nuclei > Nuclear Waste

Water cools the spent rods, and also acts as a radiation shield to reduce the radiation levels.

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Nuclear Fusion

Nuclear Fusion

How do fission reactions and fusion reactions differ?

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Fission and Fusion of Atomic Nuclei > Nuclear Fusion

Fusion occurs when nuclei combine to produce a nucleus of greater mass. In solar fusion, hydrogen nuclei (protons) fuse to make helium nuclei and two positrons.

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Fusion reactions, in which small nuclei combine, release much more energy than fission reactions, in which large nuclei split.

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The use of controlled fusion as an energy source on Earth is appealing.

• The potential fuels are inexpensive and readily available.

• The problems with fusion lie in achieving the high temperatures necessary to start the reaction and in containing the reaction once it has started.

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Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

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25.3 Section Quiz.

1. One of the control mechanisms for a sustainable nuclear chain reactor involves slowing down the released neutrons so they may be captured by other nuclei. This is done using

a. moderators.

b. shielding.

c. absorbers.

d. control rods.


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25.3 Section Quiz.

2. Spent fuel rods are stored in

a. lead-lined containers.

b. deep pools of water.

c. thick concrete bunkers.

d. cadmium or graphite containers.


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25.3 Section Quiz.

3. Choose the correct words for the spaces. In solar fusion, _______ nuclei fuse to form _______ nuclei.

a. helium, hydrogen

b. hydrogen-1, hydrogen-2

c. hydrogen, helium

d. hydrogen-1, hydrogen-3

END OF SHOW

slide 1 of 20 chemistry 25.3. © copyright pearson prentice hall slide 2 of 20 fission and fusion of...

Documents

fission reactions

nuclear fission chain

nuclear power plant

solar fusion

nuclear reaction

helium nuclei

small nuclei

large nuclei