Chem SAT
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Created by:
asianeekamkee on June 14, 2012
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32 terms
Terms | Definitions |
|---|---|
 Fluorescence | Emission of light when exposed to some exciting agency |
| Phosphorescence | Emission of light after the exciting agency is removed |
| Uranium | used to determine whether phosphorescent substances emitted X-rays while phosphorescing Produced emission that could penetrate lightproof paper and even thicker materials |
| What did uranium produce? | Ionization |
| How did uranimum, which produced ionization detect intensity of invisible emisson? | It detected it by ionizing effect- discharge of changed electroscope, or degree of darkening of a photographic plate |
| What was the purpose of ionization from uranium? | To determine intensity of invisible emission |
| What was uranium's emission like? | Continuous and permanent- required no energy from external source. Used tons |
| What was the signifigance of uranium's emission? | to isolate two new elements; radium and polonium both radioactive |
| Alpha particle | huge mass (4amu) low penetration power- penetrates body tissues of .05, but blocked by paper and clothes attracts electrons but doesn't replelled by nucleus; 100,000 ionizations per centimeter 5 cm in air |
| Beta particle | 0 mass weak b/c of high velocity penetrates 4 mm thick tissues, blocked by metal foils produces 100 ionizations per contimeter 12 m |
| Gamma radiation | 0 mass- electromagnetic radiation not a particle weak- gives energy to electrons- perform ionization same velocity of visible light -can penetrate 13 cm of lead beta particles- than gamma rays emit together |
| What happens when a beta particle is added? | Atomic mass doesn't change b/c neutrons replaced by proton Atomic # increases b/c of additional p+ |
| Photographic plate | uses this to find beta and gamma rays tracks Viewed under high-power microscope beta and gamma rays cause silver bromide grains to scatter Alpha causes silver bromide to make definite track |
| What led to the discovery of radioactivity? | Fogging of a photographic emulsion |
| Scintillation counter | Fluorescent screen showing presence or electrons and X-rays Viewed w/. magnifying eyepiece- scintillation (small flashes of light) observed- can count and detet prescence of alpha |
| Geiger counter | Determines individual radiation has fine wire of tungsten mounted along axis of metal tube conataing gas at reduced pressure- |
| Why is the giger counter hasve 1000 volts? | Applied so tube is negative w/ respect to wire. volate high so electorns produced accelarted by electric field |
| What happens when the field is strongest in a geiger counter? | Accelerated particles produce more ions, positive ones go to walls, negative ones collected by wire |
| How are the particles identified if it gives rise to the same avalanche of ions? | Type of particle can't be identified, but individual can be detected |
| What's a radon? | Sponatenous disintegration produces this. This is left over of an atom after half-life |
| What's a half-life? | time required for half of atoms to decay. |
| What's transmutation? | conversion of element to new element, produced artificially by bombarding nuclei of substance w/ various particles form particle accelerator |
| What is binding energy? | This is formed from it's compponent particles if you add masses of components and compare sum w/ actual mass of nucleus formed- small difference in figures |
| How do you convent difference in mass to energy | E=mc2 (squared) E is energy m is mass c is velocity of light (how fast is light) |
| How much binding energy does lightest to heviest elements have? | Lightest and Heaviest elements- smallest binding energy per nuclear paritcle- less stable Intermediate atomic masses- greatest binding energy |
| What does even-odd number of protons have to do with stablility of nucleus? | MANY stable have even numbers of protons and neutrons LESS FREQUENT stability of EVEN NUMBER OF PROTONS and ODD NUMBER OF NEUTRONS Only a FEW stable nucli have ODD NUMBERS OF PROTONS and NEUTRONS |
| What molecule is most used in radioactive dating? | Carbon-14 because it has a half-life of 5,700 |
| What is fission? | Splitting of a heavy nucleus into two or more lighter nuclei |
| What is fusion? | combination of light nuclei Hydrogen bombs only achieved through this |
| How do you overcome repulsive forces of two nuclei? | Extremely high temperatures and pressures |
| Where does the energy released in a nuclear reaction come from? | Comes from fractional amount of mass converted into energy Convert matter into energy |
| Which is greater, energy released during nuclear reactions, or energy released during chemical reactions? | Enery released during nuclear reactions. |
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