Module 8

Module 8—Nuclear Decay, Energy, and the Standard Model of the Atom

 

Big Picture

 

The question marks on the balls in this photo represent the unknown. What do you suppose is inside each of them? How could you find out?

 

Now imagine they are so small that you can’t even see them with an electron microscope, never mind an optical one. Imagine they are held together by the strongest fundamental force in the universe, yet sometimes they spontaneously break down into smaller balls.

 

To study how they are arranged, you shoot other small balls at them and see how they scatter. Then you investigate the results when the balls spontaneously break down into smaller pieces. You apply this understanding to developing new and innovative technologies that can save lives, identify unknown chemicals, and generate enormous amounts of power.

 

The balls can be split apart and they can be fused together; and every ball has an opposite twin, what we would call its anti-ball. If any ball should ever meet its anti-ball, they would both be annihilated, releasing large amounts of energy.

 

With collisions of sufficient energy, the balls can be smashed open, revealing the inner particles. These inner particles can then be smashed again and again using higher and higher energy collisions to release the increasingly smaller, fundamental particles held together by incredible forces.

 

Along the way, theories and models evolve as you try to understand the composition of the balls and the fundamental forces that interact with them. Yet the question mark remains, symbolizing that you are still unable to verify all the parts in a theory that tries to capture the relationship between the fundamental particles of matter and the fundamental forces (such as gravity) that extend throughout the universe.

 

If you have not put it together already, the yellow balls represent atoms that are held together by a strong nuclear force. Atoms undergo alpha and beta decay and can release enormous amounts of energy when they split apart or fuse together. The regular matter that makes up these atoms is matched by antimatter, which will annihilate them if they meet. Massive particle accelerators are used to smash them, revealing protons that can be smashed again, revealing the fundamental quarks that make up hundreds of subatomic particles.

 

More experimentation and theory suggest the presence of other mediating particles thought to carry the fundamental forces, such as gravity and electromagnetism. Some of these particles have been observed, others have not; but, together, they all contribute to the ongoing investigation and understanding of what makes up matter.

 

By the end of Module 8 you will be able to describe the investigations and evidence that are part of the ongoing development of theories and models related to the fundamental structure of matter. As you are working in Module 8, you will explore the developing models of the atom in the context of the following questions.

• Which components make up the nucleus of an atom and what keeps them from coming apart?
  
  

• What are alpha and beta decay? How do they relate to the conservation of mass and energy?
  
  

• What is half-life and how does it relate to dating organic and inorganic material?
  
  

• Why are nuclear fission and fusion reactions so powerful?
  
  

• How is it possible to probe the subatomic world in search of the fundamental particles that make up protons and neutrons?
  
  

• How does the discovery of antimatter and subatomic particles inform the latest models concerning the structure of matter?

Module Assessment

 

Each lesson has a teacher-marked assignment, based on work completed in the lesson. In addition, you will be graded on your contributions to the Discuss section of each lesson.

 

You will also be asked to complete Self-Check or Try This questions, which you should place in your Physics 30 course folder. These are not formally assessed but are a valuable way to practise the concepts and skills of the lesson. These activities can provide you with reflective feedback on your understanding of the lesson work.

 

You will be marked for your lesson work on the following items:

• Module 8: Lesson 1 Assignment

• Module 8: Lesson 2 Assignment

• Module 8: Lesson 3 Assignment

• Module 8: Lesson 4 Assignment

At the end of the module you will complete a module assessment that consists of two Diploma Exam-style written-response questions. The first question will assess your ability to apply the principles of conservation of mass-energy and conservation of momentum to a fusion reaction and the second question will assess your knowledge of decay curves and half-lives of radioactive elements. See the Module Summary and Assessment page for more information. If you have any questions contact your teacher.

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