NOTES - Out 5 - Nuclear Reactions.doc

(1)

IV. Outcome 5 – Nuclear Reactions.

A) Difference between Chemical reactions & Nuclear reactions:

Chemical Reactions Nuclear Reactions

What part of the atom is involved?

Valence Electrons only Nucleons

What changes?

Atoms rearrange into new Atoms may change into molecules but the atoms atoms of a different element stay the same

How much energy is involved?

A small amount A very large amount

B) Nuclear Fusion – the combining of lighter nuclei particles into heavier nuclei particles under very high temperature (27 million o_{F or10-15 million}o_{K) and very high pressure} (200-340 billion times earth’s surface pressures).

Basic Fusion equation:

H1_{+ H}1_+H1_{+ H}1__He4_{+ Energy}

…… Fusion specifically…..

The amount of energy from the fusion equation is calculated with E=mc2 E =

m= c=

He + Energy

H

+

Each H atom has a mass of 1.008 AMU. So, 4 H = mass of 4.032 AMU

During a Nuclear Fusion reaction there is a “loss” of .029 AMU.

This “lost” mass is converted to ENERGY. Combined mass

of 4.032 AMU

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1) Source of the Sun’s energy (and all stars) = Nuclear Fusion.

2) Fusion of elements smaller than Iron (Atomic mass 56) releases energy. 3) Fusion involving elements larger than Iron need energy.

Example 1: Nuclear reaction involving C12_{and Ne}20_{is: FUSION or FISSION} Example 2: Nuclear reaction involving Mo96_{and Sn}119_{is: FUSION or FISSION} C) Fusion on Stars and making elements.

1) Sun-like mass stars – Fusion involves: Hydrogen to Helium, then Helium to Carbon. (3 He4__C12₎

2) Very massive stars – Fusion involves:

Hydrogen -> Helium -> Carbon - > Neon -> Oxygen -> Silicon –> Iron 3) Elements bigger than Iron are made in Supernova explosions.

D) Nuclear Fission – Breaking of a large atom’s nucleus (decaying) into smaller pieces. 1) Elements heavier than iron will release energy when the nucleus is broken.

2) Chain Reaction:

a) Fission starts when a neutron hits a nucleus with enough energy to break the nucleus. b) The nucleus breaks into two smaller pieces (with protons and neutrons) and releases

extra neutrons.

c) If the extra neutrons crash into other nuclei, more neutrons are released to crash into other nuclei causing a Chain Reaction.

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IV. Outcome 5 – Nuclear Reactions.

A) Difference between Chemical reactions & Nuclear

reactions:

Valence Electrons only

Nucleons

What changes?

(4)

Valence Electrons only

Nucleons

What changes?

Atoms rearrange into new

Atoms may change into

molecules but the atoms

atoms of a different element

stay the same

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Valence Electrons only

Nucleons

What changes?

Atoms rearrange into new

Atoms may change into

molecules but the atoms

atoms of a different element

stay the same

(6)

What changes?

B)

Nuclear Fusion

– the combining

of

lighter nuclei particles into

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What changes?

B) Nuclear Fusion – the combining of lighter nuclei particles into heavier nuclei particles

under

very high temperature

(

27 million

o

F

or10-15 million

o

_K

) and

very high

(8)

Basic Fusion equation:

H1_{+ H}1_+H1_{+ H}1__He4_{+ Energy}

…… Fusion specifically…..

The amount of energy from the

fusion equation is calculated with

E=mc

2

E = ________________

m=________________

c=________________

He + Energy

H

+

Each H atom has a mass of 1.008 AMU. So, 4 H = mass of 4.032 AMU

During a Nuclear Fusion reaction there is a “loss” of .029 AMU.

This “lost” mass is converted to ENERGY. Combined mass

of 4.032 AMU

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The amount of energy from the fusion equation is calculated with E=mc2 E = Energy

m=mass

c=speed of light

1) Source of the

Sun’s energy

(and all

stars) =

Nuclear Fusion

.

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B) Nuclear Fusion – the combining of lighter nuclei particles into heavier nuclei particles under very high temperature (27 million o_{F or10-15 million}o_{K) and very high pressure} (200-340 billion times earth’s surface pressures).

1) Source of the Sun’s energy (and all stars) = Nuclear Fusion.

2) Fusion of elements

smaller than

Iron

(Atomic mass 56)

releases

energy

.

3) Fusion involving elements larger

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2) Fusion of elements smaller than Iron (Atomic mass 56) releases energy. 3) Fusion involving elements larger than Iron need energy.

Example 1: Nuclear reaction involving C

12

_{and Ne}

20

is: FUSION or FISSION

Example 2: Nuclear reaction involving Mo

96

_and

(12)

B) Fusion on Stars and making

elements.

1)

Sun-like mass stars

– Fusion

involves: Hydrogen to Helium, then

Helium to Carbon. (3 He

4

_

_C

12

₎

2)

Very massive stars

– Fusion

involves:

Hydrogen -> Helium -> Carbon - >

Neon -> Oxygen -> Silicon –> Iron

3) Elements bigger than Iron are made

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2) Very massive stars – Fusion involves:

Hydrogen -> Helium -> Carbon - > Neon -> Oxygen -> Silicon –> Iron 3) Elements bigger than Iron are made in Supernova explosions.

D)

Nuclear Fission

– Breaking of a

large atom’s nucleus

(decaying) into

smaller pieces

.

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C) Nuclear Fission – Breaking of a large atom’s nucleus (decaying) into smaller pieces.

1) Elements

heavier than iron

will

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C) Nuclear Fission – Breaking of a large atom’s nucleus (decaying) into smaller pieces. 1) Elements heavier than iron will release energy when the nucleus is broken.

2) Chain Reaction:

a) Fission starts when a

neutron

hits

a

nucleus

with enough energy to

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2) Chain Reaction:

a) Fission starts when a neutron hits a nucleus with enough energy to breaks the nucleus.

b) The nucleus breaks into

two

smaller pieces

(with

protons

and

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b) The nucleus breaks into two smaller pieces (with protons and neutrons) and releases extra neutrons.

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b) The nucleus breaks into two smaller pieces (with protons and neutrons) and releases extra neutrons.

c) If the extra neutrons crash into other nuclei, more neutrons are released to crash into other nuclei causing a Chain Reaction.