CHEM 1030 Cagg Chapter 3.1-3.4 Notes
CHEM 1030 Cagg Chapter 3.1-3.4 Notes Chem 1030
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This 4 page Class Notes was uploaded by Amy Notetaker on Monday February 8, 2016. The Class Notes belongs to Chem 1030 at Auburn University taught by Brett A Cagg in Spring 2016. Since its upload, it has received 76 views. For similar materials see Fundamental Chemistry I in Chemistry at Auburn University.
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Date Created: 02/08/16
Lecture/Book Notes: Chapter 3 (2/1/16 and 2/3/16) CHEM 1030 Cagg Highlighted: Vocab ----- Highlighted: Formulas/Numbers These notes will cover ONLY section 3.1-3.4, since those are the ones we need to know for the test! Section 3.1 v Energy and energy changes • All forms of energy are either potential energy or kinetic energy. - Kinetic energy: results from motion o Ex: an apple that is thrown in the air ▯ ▯ o Formula: E = ▯u (▯m” is the mass, “u” is the velocity) o An apple, which has a mass of 30 g, is thrown in the air at the velocity of 10 m/s, what is the kinetic energy? ▯ ▯ ▯ ▯ § E▯= mu▯à E = ×(3▯g)×▯10m s) à E = 1500 J ▯ ▯×▯ ▯ § The SI unit for energy is Joules (J), which is ▯▯ - Potential energy: is the energy an object has at a still position o Ex: an apple that is sitting on the kitchen counter o There are 2 types of potential energy: § Chemical energy: energy which is stored in the structural units of chemical substances § Electrostatic energy: energy which results from the interaction of charged particles ▯ ▯ - Formula: E ▯▯ ▯ ▯ (The product of 2 charges divided by the ▯ distance between the) - Potential energy and kinetic energy are interconvertible o Ex: A swing at rest has potential energy, once it is pushed it has kinetic energy - The law of conservation of energy: energy is interconvertible; however the total amount of it in the universe can never change nor can it be created or destroyed Section 3.2 v The nature of light • The light that we can see with our eyes is referred to as visible light • Electromagnetic spectrum: contains a small part of visible light, radio waves, microwave radiation, x-rays, gamma rays, infrared and ultra violet radiation. All of these transmit energy in the form of waves. - Ultra violet radiation: can cause sun burn - Microwave radiation: used to cook and reheat food - X-rays: used for medical diagnoses - Gamma rays: emitted from some radioactive materials v Properties of waves • Waves are characterized by their frequency, amplitude, and wavelength - Frequency: (ν) is the number of waves which pass through a certain point in the time frame of 1 second - Wavelength: (λ) is the distance between two peaks or two troughs - Amplitude: is the vertical distance from the middle of the wave to the peak or trough ▯ • The speed of light through a vacuum is c = 2.99792458 × 10 m/s • The speed, wavelength, and frequency are related through this formula: c = λ ν - Both λ and ν are expressed in meters (m) and reciprocal seconds (s ) ▯▯ - Visible wavelengths are expressed in nanometers (nm) - Microwave and x-ray wavelengths are expressed in centimeters (cm) v The electromagnetic spectrum • Electromagnetic wave: has both an electric field component and magnetic field component - The two components have the same wavelength and frequency, but travel in perpendicular planes v The double split experimen t • When two light sources pass through two closely spaced slits, the result is a series of dark and light lines (interference pattern) • Constructive interference: when the two light waves are in phase (giving rise to the light lines) • Destructive interference: when the two light waves are out of phase (give rise to the dark lines) • Long wavelengths have lower frequencies • Short wavelengths have higher frequencies Section 3.3 v Quantization of energy • Blackbody radiation: electromagnetic radiation a solid emits when it is heated • The amount of energy that an object gives off, is determined by the wavelengths of the radiation • Radiant energy can be emitted or absorbed only in small quantities • Quantum: the smallest amount of energy which can be emitted or absorbed in the form of electromagnetic radiation • The energy of one quantum energy is given by the formula: E = hν ▯▯▯ - “h” is Plank’s constant which is 6.63×10 J ∗ s - “ν” is the frequency of the radiation • Energy is always emitted in whole number multiples of hν v Photons an d the photoelectric effect • The photoelectric effect: when electrons are ejected off of a metal surface due to light exposure • Threshold frequency: the frequency at which the light that ejects the electrons has to be • Photons: the little particles in a beam of light, and the energy a photon has is expressed by this formula: E ▯▯▯▯▯▯= hν - “h” is Plank’s constant which is 6.63×10 ▯▯▯J ∗ s - “ν” is the frequency of light - When you shoot a beam of light onto the wall, its more like you shot a long tube of photons on the wall • When the light hits the metal surface and knocks the electrons loose allowing them to eject off the metal surface, the electrons acquire kinetic energy to do that, here is the formula: hν = KE + W - "hν" is the photon’s energy - "KE" is the kinetic energy - "W" is the energy which binds the electrons to the metal - The more energy a photon has, the more kinetic energy the ejected electron has v Bohr’s theory of the hydrogen atom • Emission spectra: the glow which is produced after a hot iron bar is removed from a fire v Atomic line spectra • Line spectrum: the emission of light at certain wavelengths • Each element has its own unique emission spectrum; these are like an element’s fingerprint, due to the unique lines each element gives off. - If you need to find the identity of an element, look at the unknown’s emission spectra lines, and try to match it up with a known element • To calculate visible wavelengths and all of hydrogen’s spectral lines, use the Rydberg Formula: ▯ = R ( ▯ - ▯ ) ▯ ▯ ▯▯ ▯▯ - “λ” is the wavelength of a line spectrum - “R▯” is the Rydberg constant - “n▯and n ▯ are positive integers, where n i▯ greater than n ▯ v The line spectrum of hydrogen • The ground state: is where the electron is least active, from here is where it jumps to a more excited state • The excited state: is the levels above the ground state to which the atom jumps • The emission process of a hydrogen atom can be shown through this formula: ΔE = E −▯E ▯
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