MSU CEM 141 FINAL EXAM WITH COMPLETE SOLUTIONS

MSU CEM 141 FINAL EXAM WITH COMPLETE SOLUTIONS scientific question can be answered by doing experiments, making observation, taking measurements, etc. in a replicable way Lights acts as what? Particle and wave. scientific model drawing, graph, diagram, equation. represent many chemical entities. Wavelength The distance (m) of waves from peak to peak. Short: x-ray (red), long: infrared (blue) Short - higher energy Long - lower energy scientific theory A well tested concept that explains a wide range of observations (explains why). changes with time. Explains the underlying cause of a range of phenomena Frequency (V) The number of wavefronts per second. Highest: x-ray scientific law A theory that has been tested by and is consistent with generations of data. a rule that describes a pattern in nature (explains what) Velocity of Light C = 3.00 X 10^8 = wavelength X frequency scientific explanation claim, evidence, reasoning Amplitude The intensity, height of peaks of waves. Highest: blue light size of an atom 0.1 x 10^-9m Energy of Wave (J) Increases as frequency increases and as wavelength decreases. Highest: x-ray Greek philosophers atomic theory -first atomic theory -elements: earth, fire, water, air -constantly in motion -made of mostly empty space Range of Wavelengths 10^-16 - 10^8 = 24. Only a third are visible Black Body Radiation When a mass is heated it emits a type of EM radiation, at very high temps the mass becomes "white hot" because all wavelengths of visible light become equally intense molecular structure of a substance determines ___ the observable properties atom smallest distinguishable part of an element Photoelectric Effect Metals emit electrons when electromagnetic radiation shines on the surface, light is transfers energy to the electrons at the metal's surface where it's transformed into KE that gives the electrons enough energy to leave the atom Depends on frequency not intensity how many atoms are naturally occurring? 91 naturally occurring elements How many electrons are emitted if the light is below it's threshold frequency no matter the intensity? None. Dalton's atomic theory (1800s) -elements composed of small, indivisible, indestructible, particles (atoms) -all atoms of each element are identical (mass/properties) -no subatomic particles -compounds are formed by combos of atoms from 2+ elements -chemical reactions occur from rearrangement of atoms What increases the number of electrons to be emitted by the photoelectric effect? Intensity. JJ Thomson -first person to provide evidence of electron -cathode ray tube -plum pudding model