Day 6 GHSGT Review Energy Transformations

Transfer of Energy Heat is transferred three ways…

Conduction the movement of heat energy through a substance by direct contact between the particles Ex. – a candle heats one end of a metal rod and the other end gets hot because of the transfer of heat

Convection the transfer of heat energy by the actual movement (or currents) of heated matter Ex. – The water in the bottom of a teapot becomes hot creating currents which carry heat upward

Radiation transfer of heat energy by waves from an area of high temperature to an area of low temperature Ex. – Heat from a space heater, fireplace, or the sun

is the spontaneous release of energy and particles from the nucleus of an atom.

ISOTOPES  Atoms of the same element with a different number of neutrons.  Ex: carbon-12 & carbon-14  Carbon-12  6 protons  6 neutrons  6 electrons  Carbon-14  6 protons  8 neutrons  6 electrons

The nucleus of an atom can be unstable is there are too many neutrons for the number of protons. An unstable nucleus will be radioactive. All elements with an atomic number greater than 83 are radioactive

3 Types of Radioactivity Radioactive Decay  ALPHA PARTICLE ( α )  BETA PARTICLE ( β )  GAMMA RAYS ( γ )

ALPHA PARTICLE  2 protons & 2 neutrons  nucleus of a helium atom  weakest type of radiation  can be stopped by a piece of paper  12 inches max. distance travel

What happens to the numbers of particles in the nucleus after alpha decay?

BETA PARTICLE  an electron emitted from the nucleus  A neutron splits into a proton & electron  The electron is expelled out of the nucleus  The proton stays and increases the number of protons by one.  The atomic number of the element increases by one  The element changes into the next higher element on the periodic table.  100x stronger than an alpha particle

What happens to the numbers of particles in the nucleus after beta decay?

Gamma Rays  An electromagnetic wave  A packet of energy  The energy readjustment in the nucleus  Most powerful form of radiation  The sun is a great source of gamma radiation

Gamma Ray Photography From Space

Antoine Henri Becquerel  In 1896, radioactivity was first discovered.  Used uranium salts = placed them near a photographic film plate.  exposed the film (below)  Awarded Nobel Prize in 1903 in Physics

Pierre & Marie Curie (1898)  Discover the radioactive properties of radium & polonium  Together awarded the Nobel Prize in 1903 (physics) along with Henri Becquerel  Marie is award a second Nobel Prize in 1911 (chemistry)  Pierre is killed in an accident in 1906, Marie continues working with radioactive substances.

Transmutation  = changes from one element to another element during α and β decay.  Alpha Decay = mass number decreases by 4 and the atomic number decreases by 2  Beta Decay = mass number does not change and the atomic number increases by 1

Alpha Decay  Uranium-238 has 92 protons  After alpha decay (2 protons & 2 neutrons leave the nucleus)  Becomes Thorium-234 and has 90 protons

Beta Decay  Carbon-14 has 6 protons & 8 neutrons  After beta decay (a neutron is split into a proton and electron & the electron is expelled from the nucleus)  Becomes Nitrogen-14 and has 7 protons and 7 neutrons

Half Life = the time it takes for one half of the mass of a radioactive substance to decay. Ex: carbon-14 = 5730 years 100 gram sample –In 5730 yrs = 50 grams C-14 & 50 grams N-14 –In11,460 yrs = 25 grams C-14 & 75 grams N-14 –In 17,190 yrs = 12.5 grams C-14 & 87.5 grams N-14

The Decay of Strontium-90 Number of half- lives Elapsed TimeAmount of strontium-90 present g 129 years5.0 g 258 years? ??.625g

Nuclear Reactions  Nuclear Fission  Nuclear Fusion

Nuclear Fission Nuclear Fission  = the splitting of the nucleus into two smaller nuclei  Neutrons are used to split the nucleus  Additional neutrons are released to continue on to hit/split other nuclei

Chain Reactions  Critical Mass ( required ) = concentration of radioactive atoms in a sample.  Controlled Chain Reaction = many of the neutrons that are produced are absorbed in “control rods” prevent excess energy to be released. Ex. Nuclear Power Plants  Uncontrolled Chain Reaction = all the neutrons are allowed to continue to hit/split other nuclei causing massive amounts of energy to be released all at once.  Ex. Atomic Bomb (used on Japan in 1945)

Controlled Chain Reaction

Uncontrolled Chain Reaction

Nuclear Fusion Nuclear Fusion  = the joining of two smaller nuclei into a single larger nucleus  Extremely more powerful release of energy than fission  Requires a temperature of 10 million degrees Celsius  Also known as a thermonuclear reaction  ex: H-bomb and the sun/stars

Fusion Explosions

World War Breaks out in Europe in 1939 Szilard drafted a letter in consultation with Albert Einstein that was addressed from Einstein to President F.D. Roosevelt and which warned him of the possibility of nuclear weapons (the "Einstein Letter"). Einstein LetterEinstein Letter This letter was delivered to FDR on October 11, 1939, and ten days later the first meeting of the Advisory Committee on Uranium (the "Briggs Uranium Committee") was held in Washington, DC on Pres. Roosevelt's order.

“The Gadget”

Code Name = Trinity  July 16, At 5:29:45 a.m. “The Gadget” was detonated in the first atomic explosion in history. The explosive yield was Kt, vaporizing the steel tower.

August 6, 1945  “Little Boy” is used on Hiroshima, Japan  Dropped from the B-29 bomber named “The Enola Gay”  5 mile circle of destruction  est. 78,000 killed & 70,000 injured

August 9, 1945  “Fat Man” is used on Nagasaki, Japan  2 mile circle of destruction  40,000 killed & 25,000 injured  Japan unconditionally surrenders a few days later & WWII is officially over

Further Nuclear Developments  August 1949 = Soviet Union tests their first atomic bomb after spies deliver US secret bomb blue-prints  November 1952 = United States the first Hydrogen bomb (H-bomb) 10 MT in strength, USSR tests their first H-bomb in Aug  Other Atomic weapons countries include Great Britain, China, France, India, Pakistan, and possibly Israel. North Korea and Iran are currently in the news for seeking nuclear capabilities.