PSC 4010 Nuclear Technology: A matter of Energy

PSC 4010: Chapter 4 Goals: _ SWBAT classify examples of changes in matter (physical, chemical, nuclear) _SWBAT distinguish between different nuclear reactions (radioactivity, fission, fusion) _SWBAT compare the nature, speed, electric charge and penetrating power of alpha and beta particles, as well as gamma rays (and X rays). Also, to know how each can affect matter _SWBAT calculate the decay time for an isotope given its half-life _SWBAT identify the radioactive element involved, the type of radiation emitted and the new element formed for a given decay process _ SWBAT understand the relationships between energy released in a nuclear reaction, mass defect, and stability of resulting isotope

PSC 4010: Chapter 4 Changes in matter can be: (Table on page 2.37)  Physical (appearance)  Chemical (electrons in last shell)  Nuclear (nucleus)

PSC 4010: Chapter 4 Physical changes (p. 4.3 – 4.7):  Superficial change  Needs little amount of energy  DOES NOT change nature of element or compound  DOES NOT affect the properties of element or compound  Changes state of matter

PSC 4010: Chapter 4 Physical changes: Sublimation Condensation Fusion Evaporation Deposition Solidification

PSC 4010: Chapter 4 Chemical changes (p. 4.8 – 4.12):  More profound change  Needs more energy  Involves electrons in last shell  NEW SUBSTANCES are formed  Evidences of chemical change: _change of color _gas release _formation of precipitate _change of temperature

PSC 4010: Chapter 4 Chemical changes: P C P C C P

PSC 4010: Chapter 4 Chemical changes: Ionization: when an atom gains or loses one or more electrons

PSC 4010: Chapter 4

Nuclear changes (p – 4.16):  Most profound change  Needs much more energy  Involves particles in nucleus!  An element is changed into another  ALL involve emission of radiation (which can be harmless, dangerous, or lethal)

PSC 4010: Chapter 4 Radioactivity (natural): (p – 4.37)  spontaneous nuclear change  nucleus of a very large and unstable isotope disintegrates into a lighter and more stable element  emits radiation in the form of particles (alpha and beta) and in the form of energy (gamma rays)

PSC 4010: Chapter 4 Radioactivity emissions: (Table 4.2 on page 4.21) Alpha particlesBeta particlesGamma rays 2 protons, 2 neutrons (He nuclei) ElectronsWave Positively chargedNegatively chargedNo charge (highest energy) Deflect toward negative pole in an electric field Deflect toward positive pole in an electric field No deflection Not too penetratingMore penetratingMost penetrating Stopped with paper sheetStopped with 2.5 cm thick wood Stopped with 1 m thick concrete or lead block

PSC 4010: Chapter 4

Radiation in an electric field: (Figure 4.7 on page 4.20)

PSC 4010: Chapter 4 Nature of radiations (waves) (p – 4.25): _Gamma rays are electromagnetic waves (like light), and therefore they behave as if they have no mass, they are just radiation (energy) _Gamma and X-rays have highest frequencies, and energies of the whole electromagnetic spectrum. Therefore they are called IONIZING RADIATIONS _Our eyes only see the colors contained in the narrow visible part of said spectrum

PSC 4010: Chapter 4 Nucleus Gamma rays Electrons Gamma rays Beta rays Alpha rays + +

PSC 4010: Chapter 4 Nature of radiations (particles) (p – 4.27): _Alpha and Beta particles have a mass (particles) _Alpha particles are very heavy compared to Beta particles, and both more than Gamma rays (massless) _Alpha and Beta particles can physically remove electrons from atoms. Therefore they are also considered IONIZING RADIATIONS

PSC 4010: Chapter 4 Nuclear changes: Gamma rays Chemical change Because X-rays can also ionize matter

PSC 4010: Chapter 4 Uranium-238 decay chain (p – 4.32): _Transmutation: Process by which an unstable radioactive element transforms into a more stable one _During each step of the transmutation Alpha, Beta and Gamma rays (or neutrons) are emitted _During the transmutation there is CONSERVATION OF MASS (number of protons and neutrons is the same before and after transmutation)

PSC 4010: Chapter 4 Uranium-238 decay chain (p – 4.32): Transmutation of an Alpha particle  Emission of alpha particles (2 protons, 2 neutrons)  Mass number decreases by four (2 protons + 2 neutrons)  Atomic number decreases by two (2 protons) Ex:

PSC 4010: Chapter 4 Uranium-238 decay chain (p – 4.32): Transmutation of an Beta particle  Emission of beta particles (1 electron)  Mass number DOES NOT change  Atomic number increases by one (1 neutron is converted into 1 proton) Ex:

PSC 4010: Chapter 4 Nuclear changes: Decreases by two (2) Increases by one (1) Gamma rays do not affect the mass of the atom

PSC 4010: Chapter 4 Beta decay Increases by one (1) Increases by one (1). One neutrons transforms into one proton Atomic mass remains the same Mass number remains the same

PSC 4010: Chapter 4

Half-life of radioactive isotopes (p – 4.37): _Half-life of radioactive isotopes: Time it takes to lose half of its mass Ex: Iodine-131 has a half-life of 8 days. Therefore, if you have 40kg, _after 8 days you end up with 20kg _after 8 more days (16) you end up with 10kg _after 8 more days (24) days you end up with 5kg _after 8 more days (32) you end up with 2.5kg _after 8 more days (40) s you end up with 1.25kg _after 8 more days (48) you end up with 0.625kg _and so on until it is completely transformed _The longer the half-life, the lower the emissive radiation (and vice versa) _U-238 has a half-life of 4.5 billion years!

PSC 4010: Chapter 4

4.5 X 10 9 years 10 9 years

PSC 4010: Chapter X s 8 days s days

PSC 4010: Chapter 4 Nuclear changes: 125 g g

PSC 4010: Chapter 4 Transmuting matter (p – 4.40): _Natural transmutations are natural radioactivity, or spontaneous transformation of unstable elements (Rutherford demonstration) _Artificial transmutations are forced transmutations produced in a laboratory or man-made environment (NOT spontaneous) Ex: Cobalt-60 and Iodine-131 are artificially made radioactive isotopes widely used in medicine

PSC 4010: Chapter 4 Nuclear Fission (p – 4.44): _Fission: to break into smaller parts _Nuclear Fission: Atoms nuclei broken into smaller atoms (bombarding nuclei with particles, usually neutrons) _Nucleus split as a result of fission, produces LOTS of radiation emission and Large amounts of energy released _These nuclear fission reactions can sometimes be considered chain reactions, as they produced more neutrons that will in turn split more nuclei of the same element _Chain reactions can be used to produced electricity for millions of people or just used to produce BOMBS

PSC 4010: Chapter 4 Nuclear Fusion (p – 4.45): _Nuclear Fusion: Opposite to fission, two smaller elements combine to produce a bigger and heavier one _Nuclei fusing together produces EVEN MORE energy that Fission (3 to 3.5 times for same amount of fuel) _Nuclear Fusion is how the Sun creates its energy! _Nuclear Fusion is feasible for light elements (H or He) but nearly impossible for heavier elements since these reactions require temperature values of MILLIONS degrees, and extremely high pressure. _Because of the extreme experimental conditions, nuclear fusion is also known as Thermonuclear reactions

PSC 4010: Chapter 4 Nuclear changes: Nuclear Fission is splitting a bigger atom into two lighter ones Nuclear Fusion is combining two lighter atoms into a bigger one

PSC 4010: Chapter 4 Energy involved in nuclear changes (E = mc 2 ) (p – 4.49): Nuclear forces are extremely powerful, BUT can only work at small distances. That is why bigger nuclei are unstable.  Chemical change produces high amounts of energy  Nuclear Fission produces ONE MILLION times the amount of energy of a chemical reaction with the same amount of fuel  Nuclear Fusion produces up to THREE MILLION times the amount of energy of a chemical reaction with the same amount of fuel

PSC 4010: Chapter 4 Mass defect (p – 4.49): Mass defect is the difference between the mass of the protons and neutrons by separate, and the mass of the resulting nucleus. The difference of mass is converted to Energy  The greater the mass defect, the greater the amount of energy released!  Every nuclear reaction involves the generation of a new nuclei as elements transmute into others. This means that at each step of a decay chain, energy is released as a consequence of mass defect

PSC 4010: Chapter 4 Practice Exercises for Chapter 3:  Page 4.53 – 4.60 – Ex 4.45 – 4.69