AST 105 1st Edition Lecture 3Outline of Last Lecture I. Kelvin and Helmholtza. Kelvin Scaleb. Joules c. Chemical Reactions and the Sun II. Sun’s Atmosphere a. 3 layersb. Surface Features c. Magnetic Fieldsd. Other FeaturesIII. Galileo Outline of Current Lecture I. Matter a. Atomsb. Nucleusi. Electronsii. Protonsiii. Neutronsc. Electrical chargesII. 4 Fundamental ForcesIII. Why does the Nucleus exist?IV. Nuclear ReactionsV. Proton-Proton ChainCurrent LectureMatter - Atoms can combine to form molecules- A collection of molecules constitutes matter - An example of molecule is a water molecule 2 atoms of hydrogen 1 atom of oxygen - H2O- Atom is compromised of a nucleus surrounded by electrons - Nucleus contains protons and neutrons- Electrons surround Electrons have negative charge In nucleus, protons have positive charge Neutrons have no charge (neutral = neutron)- Electrical charge [rule of thumb]: Unlike charges attract while like charges repel. This is why electrons are attracted to the protons in the nucleus. This force is due to the electromagnetic force. 4 Fundamental Forces1. Electromagnetic force2. Gravitational force 3. Strong force4. Weak force Why Does the Nucleus Exist?- Neutrons and protons are attracted to each other due to the strong force. - Strong force is much stronger than the electromagnetic force, up to a point. - The strong force is short ranged but electromagnetic force is very long ranged. - As the nucleus becomes larger, the electric force dominates the strong force; hence atoms larger than Bismuth (83) are unstable. Chemical Electric forceElectrons are transferred Nuclear Strong forceProtons/neutrons are transferred Nuclear Reactions- Fission = large nuclei split into smaller nuclei- Fusion = small nuclei joined to produce a large nuclei - Sun/stars do nuclear fusion “Gravity is like holding together the sun because it is so big. Gravity is basically driving the nuclear fusion.”o A nuclear reaction is 10 million times greater than a chemical reaction Proton-Proton Chain- Hydrogen is fused to produce helium and energy is released - Positron collides with an electron to produce gamma rays- Another positron collides with (2H) this happens twiceEinstein’s equation = E=MC2 important note to
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