9th Grade Physical Science
Unit 6 The Power of the Nucleus
#6 Fusion: Source of all Elements
#6
To Begin
You just watched a demonstration involving the combustion of hydrogen gas. If you recall,
reactions called combustion reactions always involve oxygen gas. In this case, hydrogen gas (H2) reacts
with oxygen gas (O2) to form water. Write the balanced chemical equation for this reaction below:
The combustion of hydrogen releases more energy then it absorbs…it is an exothermic reaction. What
evidence did you observe to support that the reaction is an exothermic reaction.
Hydrogen combustion produces a powerful exothermic reaction. The energy from hydrogen
combustion might one day replace the energy we get from burning gasoline! Another benefit is that the
product from this reaction is simply water; not harmful CO2 and other polluting gases!
Astronomers know that hydrogen is the fuel that produces energy in the Sun and other stars. But
the reaction in stars produces vastly more energy per hydrogen atom than hydrogen combustion. Here is a
comparison:
• When 1 gram of hydrogen combusts, the energy produced = the energy released from burning ¼
teaspoon of gasoline.
• The energy produced by 1 gram of hydrogen reacting in a star = energy from burning about 3.3
gallons of gasoline.
• That is close to 100,000 more energy from the same amount of hydrogen. And the Sun has more
hydrogen atoms than could be found on several million Earths!
Purpose
• Students will compare the energy produced from combustion to energy produced from nuclear fusion.
• Students will explore the idea of hydrogen fusion (combing hydrogen nuclei to form helium)
Process
1. Examine the trends shown in the table below with your team:
What happens at the microscopic
level
Molecules are pulled further apart
or pushed closer together
Forces pull electrons in an atom
away from one nucleus and closer
to another nucleus
Forces pull atomic nuclei apart or
push them closer together
What happens at the
macroscopic level
Phase change
(solid liquidgas
Relative amount of energy
(compared to 1 gal of gasoline)
Type of particle
involved
Relative size of
particle involved
1
molecules
10
Chemical
reactions
1-10
atoms
1
Nuclear energy
in star
100,000
nucleus
.00001
2. Refer to the table to complete this sentence: As the size of the particles involved _____________, the
amount of energy produced ______________.
3. Suppose forces caused hydrogen nuclei to collide with each other and then stay together. How many
hydrogen nuclei would it take to produce 1 helium (He) nuclei (based on mass)?________________
4. Represent your thinking in #3 with chemical symbols (H and He) and an arrow between the parent
nuclei and the daughter nucleus. Include energy where you think it belongs.
5. Nuclear fusion is the process by which individual atomic nuclei join together to form a heavier
nucleus. The fusion process releases large amounts of energy. Our closest tie with nuclear fusion is
the activity that happens in our Sun.
6. Use > or < or = to complete these sentences.
a. The number of protons in 4 H nuclei _________ the number of protons in 1 He nucleus.
b. The total mass (rounded) of 4 H nuclei ______ the mass of 1 He nucleus.
7. What is the discrepancy you notice as hydrogen nuclei fuse to become a helium nucleus?
8. Complete the highlight comments and a caption. Discuss a possible explanation for the discrepancy
you observed in #7 in your caption.
What I See:
What It Means:
Caption:
What I See:
What It Means:
9. Read #6 Nuclear Fusion Read closely and with a partner. This is your copy so be sure to
highlight. Write key terms and any questions you may have in your comp book.