Nuclear Chemistry Day 3

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Nuclear Chemistry Day 3

• Welcome! Please pick up the practice questions
  on half-lives. We will complete this prior to
  the quiz.
• Turn in your honors intent letter today.
• Hmwk Read Chapter 9 Section 2 and 3
• Test next Monday/Tuesday
• Notebook check next time
• Honors Proposal due next week.

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Warm-Up

• Complete the half-lives and radioactive decay
  practice questions.

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Agenda

• Announcements
• Warm-Up Practice Questions
• Quiz Half-lives Radioactive Decay
• Notes Fission/Fusion
• Video Nuclear Energy

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Nuclear Forces

• Protons and neutrons are tightly packed in the
  nucleus
• Unstable nuclei undergo decay by emitting nuclear
  radiation
• An element can have both stable and unstable
  isotopes
• The stability of a nucleus depends on the nuclear
  forces that hold the nucleus together these
  forces act between the protons and the neutrons.

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Why dont the positively charged protons repel
each other ?

• Strong nuclear force causes protons and
  neutrons to attract each other.
• This attraction is much stronger than the
  electric repulsion between protons

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Too many neutrons or protons can cause a nucleus
to become unstable and decay

• Nuclei with more than 83 protons are always
  unstable
• These nuclei will always decay releasing large
  amounts of energy and nuclear radiation.
• The decay results in a more stable nucleus.

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Nuclear Fission

• Fission The process of splitting heavier nuclei
  into lighter nuclei the process by which a
  nucleus splits into two or more fragments and
  releases neutrons and energy

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Nuclear Fission Video Clip Nuclear Weapons In
fission weapons, a mass of (enriched uranium or
plutonium) is assembled into a supercritical
massthe amount of material needed to start an
exponentially growing nuclear chain
reactioneither by shooting one piece of
subcritical material into another, or by
compressing a subcritical mass with chemical
explosives, at which point neutrons are injected
and the reaction begins. Nuclear Power Plants
Nuclear energy is produced when a fissile
material, such as uranium-235 (235U), is
concentrated such that nuclear fission takes
place in a controlled chain reaction and creates
heat which is used to boil water, produce
steam, and drive a steam turbine. The turbine can
be used for mechanical work and also to generate
electricity.
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Nuclear Fusion

• Fusion the process in which light nuclei
  combine at extremely high temperatures, forming
  heavier nuclei and releasing energy

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How the Sun shines Nuclear fusion is the energy
source of stars just like our own Sun. It has
a nuclear fusion reactor at its core. The
immense pressure and a temperature of 16 million
degrees C force atomic nuclei to fuse and
liberate energy. About four million tons of
matter is converted into sunlight every second.
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Nuclear Radiation Today

• Nuclear radiation is all around you. Background
  radiation is the nuclear radiation that arises
  naturally from cosmic rays and from radioactive
  isotopes in the soil and air.
• Radiation is measured in units of rems.
• Exposure varies depending on location and
  activities.

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Beneficial Uses of Nuclear Radiation

• Smoke detectors a small alpha-emitting isotope
  is used to detect smoke particles in the air.
• Disease detection radioactive tracers are added
  to a substance so that its distribution can be
  detected later. These are widely used in
  medicine.
• D\Ch09\75459.html tracer clip

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Benefits continued

• Nuclear radiation therapy is used to treat
  cancer.
• Agriculture - radioactive tracers and
  radio-isotopes are used to help scientists
  understand biological processes in plants.

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MRI image of a healthy brain
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MRI image of a brain with Alzheimers Disease
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Possible Risks of Nuclear Radiation

• Nuclear radiation can ionize atoms
• Ionization is a change in the number of electrons
  in an atom or molecule, causing the particle to
  be positively or negatively charged.
• Radiation sickness results from high levels of
  nuclear radiation
• Studies have shown a relationship between high
  levels of radiation exposure and cancer.
• (Risk is determined by amount of exposure)

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Nuclear Power

• Nuclear fission is an alternative to fossil fuels
  as a source of energy.
• Radioactive products of fission must be handled
  carefully and nuclear waste must be safely
  stored.
• Scientists are working on nuclear fusion
  reactors, but fusion reactions are difficult to
  produce in the laboratory.