Introduction to Physical Science

Monday, Wednesday, Thursday

Tom Burbinetomburbine@astro.umass.edu

• Fission – Splitting of the nucleus of a heavy atom with the release of energy

• Fusion – Combination of the nuclei of light atoms to form heavier nuclei with the release of energy

Energy Source for Sun

• Fusing hydrogen into helium– Hydrogen nucleus – 1 proton– Helium nucleus – 2 protons, 2 neutrons

• Need high temperatures for this to occur• ~10 to 14 million degrees Kelvin

http://www.astronomynotes.com/starsun/s3.htm

http://www.astronomynotes.com/starsun/s3.htm

How does Fusion Convert Mass to Energy

• What is the most famous formula in the world?

E = mc2

• m is mass in kilograms• c is speed of light in meters/s• E (energy) is in joules• very small amounts of mass may be converted

into a very large amount of energy

Who came up with it?

http://msnbcmedia3.msn.com/j/msnbc/Components/Photos/z_Projects_in_progress/050418_Einstein/050405_einstein_tongue.widec.jpg

Law

• Law of Conservation of mass and energy– Sum of all mass and energy (converted into the same

units) must always remain constant during any physical process

Reaction

• 4 protons → helium-4 + 2 neutrinos + energy

Neutrino-virtually massless, chargeless particles

Positron-positively charged electron – annihilated immediately by colliding with an electron to produce energy

Antiparticles

• Antiparticle – particle with the same mass and opposite electric charge

• Antiparticles make up antimatter• Annihilation – when a particle and an antiparticle

collide• Antimatter is said to be the most costly substance

in existence, with an estimated cost of $62.5 trillion per milligram.

Fusion reaction

• Much more complicated than 4 protons → helium-4 + 2 neutrinos + energy

Deuteron – Deuterium (hydrogen with a neutron)nucelus

Proton-Proton Chain Reaction

• This reaction occurs ~1038 times each second• It if occurred faster, Sun would run out of fuel

Neutrinos

• Neutrinos – almost massless particles• No charge• It takes a neutrino about 2 seconds to exit the Sun

Fusion

• The rate of nuclear fusion is a function of temperature

• Hotter temperature – higher fusion rate• Lower temperature – lower fusion rate• If the Sun gets hotter or colder, it may not be

good for life on Earth

What is happening to the amount of Helium in the Sun?

• A) Its increasing• B) its decreasing• C) Its staying the same

What is happening to the amount of Helium in the Sun?

• A) Its increasing• B) its decreasing• C) Its staying the same

Valence Electrons

• Electrons in the outermost occupied shell of an atom

• Forms chemical bonds

Ion

• Ion – an electrically charged particle created when an atom either loses or gains one or more electrons

Ionic Bond

• Ionic bond – chemical bond in which an attractive electric force holds an opposite charge together

Covalent Bond

• Covalent bond – a chemical bond in which atoms are held by their mutual attraction for two or more electrons share

• Covalent bonds form molecules

Metallic Bonds

• A chemical bond in which positively charged metal ions are held together within a “fluid”

• Electromagnetic interaction between conduction electrons and gathered in an "electron sea“

• Atoms "share" electrons that float about in a general electron cloud

Charges need to balance

• Na ions carry a +1 charge• Cl ions carry a -1 charge• Na+ + Cl- → NaCl (Sodium chloride)

• HCl – Hydrogen Chloride• Li2O – Lithium Oxide

• CO – Carbon Monoxide• CO2 – Carbon Dioxide

Any Questions?