Topicm8e00e48be1926666_1528449000663_0Topic

Thermonuclear reactions in the Sun

Levelm8e00e48be1926666_1528449084556_0Level

Third

Core curriculumm8e00e48be1926666_1528449076687_0Core curriculum

XI. Nuclear physics. The student:

11) describes the thermonuclear reactionthermonuclear reactionthermonuclear reaction of hydrogen transformation into helium occurring in the stars.

Timingm8e00e48be1926666_1528449068082_0Timing

45 minutes

General learning objectivesm8e00e48be1926666_1528449523725_0General learning objectives

Describes the thermonuclear reaction of hydrogenhydrogenhydrogen transformation into helium occurring in the stars.

Key competencesm8e00e48be1926666_1528449552113_0Key competences

1. Explains what kind of reactions belongs to proton‑proton chain.

2. Calculates the energy released during the nuclear fusion.

Operational (detailed) goalsm8e00e48be1926666_1528450430307_0Operational (detailed) goals

The student:

- explains the thermonuclear reaction of hydrogen transformation into helium,

- calculates the energy released during the nuclear fusionnuclear fusionnuclear fusion.

Methodsm8e00e48be1926666_1528449534267_0Methods

1. Discussion.

2. Text analysis.

Forms of workm8e00e48be1926666_1528449514617_0Forms of work

1. Individual work.

2. Group work.

Lesson stages

Introductionm8e00e48be1926666_1528450127855_0Introduction

The teacher asks the students to remind what the nuclear fusionnuclear fusionnuclear fusion is.

What the nuclear fusion is?

Procedurem8e00e48be1926666_1528446435040_0Procedure

The teacher discusses with the students what processes in the Sun arise.

The Sun emits energy which originates from a nuclear fusionnuclear fusionnuclear fusion process. The fusion occurs deep inside the core of the Sun. Inside this core the temperature reaches more than 15000000 K. Every second, 600 million tons of hydrogenhydrogenhydrogen converts into heliumheliumhelium and enormous energy is released.

The specific type of fusion that occurs inside of the Sun is known as proton‑proton fusion.

Proton‑proton chainproton‑proton chainProton‑proton chain reaction

The process starts with collisions of protons. These protons are the nuclei of hydrogenhydrogenhydrogen. In a series of steps these protons turn into helium. The mass of helium is less than the mass of colliding protons and according to the principle of mass‑energy equivalence in the fusion energy is released. The resulting energy is radiated out from the core of the Sun and distributes across the Solar SystemSolar SystemSolar System.

Proton‑proton chain reaction occurs in several steps:

1. Two pairs of protons fuse and two deuterons are formed.

2. Each deuteron collides with an additional proton to form helium ${}_{}{}^{3}He$.

3. Two heliumheliumhelium nuclei ${}_{}{}^{3}He$ fuse to create a helium ${}_{}{}^{4}He$ and two protons.

[Interactive graphics]

In proton‑proton chain two neutrinos, two positrons and gamma rays are released.

[Illustration 1]

The reactions involved in the proton‑proton chainproton‑proton chainproton‑proton chain are following:

The students calculate the released energy in the fusion of proton and deuteron.

Task 1

Calculate the energy released in the proton‑deuteron step of proton‑proton chain. The deuteron mass is 3,343583772 ∙ 10Indeks górny -27^-27 kg and the mass of proton is 1,6726219 ∙ 10Indeks górny -27^-27 kg. Use exact values of the speed of light c = 299792458 $\frac{m}{s}$. The relation between electronovolt and joule is following: 1 eV = 1,6021766208 ∙ 10Indeks górny -19^-19 J. Compare your result with the information you have already read.

Time of reaction:

The average time required for the first step of proton‑proton chain is extremely long. A hydrogen nucleus needs on the average 10Indeks górny 9⁹ years to undergo an interaction with another nucleus in order to initiate the chain. The next step is very short and in the average lasts about 1 s. In the last steps of the cycle the helium nuclei ${}_{}{}^{3}He$ needs about 400 years to produce the final helium nuclei ${}_{}{}^{4}He$.
The rate of proton‑proton chain is very low but still enough to produce huge amount of energy due to the enormous number of hydrogen atoms in the core of the Sun.m8e00e48be1926666_1527752263647_0The average time required for the first step of proton‑proton chain is extremely long. A hydrogen nucleus needs on the average 10Indeks górny 9⁹ years to undergo an interaction with another nucleus in order to initiate the chain. The next step is very short and in the average lasts about 1 s. In the last steps of the cycle the helium nuclei ${}_{}{}^{3}He$ needs about 400 years to produce the final helium nuclei ${}_{}{}^{4}He$.
The rate of proton‑proton chain is very low but still enough to produce huge amount of energy due to the enormous number of hydrogen atoms in the core of the Sun.

Lesson summarym8e00e48be1926666_1528450119332_0Lesson summary

In the proton‑proton fusion in the Sun, known as proton‑proton chainproton‑proton chainproton‑proton chain, protons in a series of steps turn into heliumheliumhelium. In this fusion tremendous amounts of energy are released.

Selected words and expressions used in the lesson plan

thermonuclear reactionthermonuclear reactionthermonuclear reaction

nuclear fusionnuclear fusionnuclear fusion

proton‑proton chainproton‑proton chainproton‑proton chain

hydrogenhydrogenhydrogen

heliumheliumhelium

relationrelationrelation

averageaverageaverage

Solar SystemSolar SystemSolar System