2019

Name: ______________________________________ Date: ________________________

Student Exploration: Nuclear Reactions

[Note to teachers and students: This Gizmo was designed as a follow-up to the Nuclear Decay

Gizmo. We recommend doing that activity before trying this one.]

Vocabulary: chain reaction, CNO cycle, catalyst, deuterium, electron volt, fission, fusion,

isotope, nuclear reaction, positron, positron emission, proton-proton chain

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

The chart to the right gives the isotope

name, element name, number of protons, and

number of neutrons of three isotopes.

1. What do you notice about the isotope

number and the sum of protons and

neutrons?

2. The element symbol for uranium-238 is . This means U-238 has a total mass of 238

and contains 92 protons. Write the element symbols for the isotopes in the table:

Hydrogen-1 Carbon-12 Uranium-235

Gizmo Warm-up

The Nuclear Reactions Gizmo simulates a particle accelerator.

Particle accelerators speed up atoms to very high velocities, then

crash the atoms together with enough energy to cause changes called

nuclear reactions. There are three particle beams available in this

Gizmo, protons, neutrons, and helium-3 nuclei.

1. Click Fire Proton to engage the first particle beam.

What happens?

2. Colliding particles don¶t alZa\s react. Click Reset, and then click Fire neutron.

A. Does a reaction occur?

B. Explain:

Isotope Protons Neutrons

Hydrogen-1 1 0

Carbon-12 6 6

Uranium-235 92 143

Alexa Nissim 6420

H E

No

The isotope number is equal to the sum of the protons and neutrons.

Proton joins nucleus

Neutron traveled through the nucleus

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2019

Activity A:

Proton-proton

chain

Get the Gizmo ready:

x Click Reset.

x Be sure Proton-proton is selected in the Reaction

menu.

Introduction: All stars turn hydrogen into helium in a process called nuclear fusion. Stars

perform this process in different ways. In stars like our sun, the proton-proton chain is used.

This reaction requires temperatures greater than 4,000,000 K to occur.

Question: How does the process of fusion turn hydrogen into helium in stars?

1. Observe: Click Fire proton and observe. What happens after the proton merges into the

nucleus?

This is a form of nuclear decay called positron emission. During positron emission, a

proton decays into a neutron. In this process, it emits a positron, which is a nearly massless

antimatter particle with a positive charge.

2. Observe: Click Reset and click Fire proton. Observe what happens. Many subatomic

particles appear frequently in nuclear reactions. Their element symbols are given below:

(Neutrinos are also produced but are beyond the scope of this Gizmo.)

Click Reset and click Fire proton. Turn on the Write equation checkbox. Based on what

you have observed, write in the equation for this reaction in the Gizmo and below.

A. Turn on Show equation. Was your predicted equation correct?

Correct your equation if necessary. The resulting H-2 isotope is called deuterium.

B. Emitted energy is reported in megaelectron volts (MeV), where one MeV is equal to

one million electron volts. How much energy is emitted in this reaction?

(Activity A continued on next page)

Neutron Positron Electron Proton

i H H 9 et

yes

1.44MeV

Proton converts to neutron, positron emitted

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