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Lab 2 - Flame Tests - Lab 2 Flame Tests Contents > Lab 2...

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4/15/13 Lab 2 - Flame Tests www.webassign.net/ebooks/wsugencheml1/lab_2/manual.html 1/6 Contents > Lab 2 - Flame Tests Lab 2 - Flame Tests Purpose To determine the identities of ions in two solutions of unknown composition by comparing the colors they produce in flame tests with colors produced by solutions of known composition. Goals To gain practice using a Bunsen burner. To observe flame test colors produced by ions in solution. To compare flame test colors produced by known ions in solution with those produced by unknown ions in solution. To use deductive reasoning to identify the unknown ions in solution. Introduction When many people hear the word radiation, their first thought is something radioactive. However, a scientist thinks about energy moving through space in a series of waves called electromagnetic (EM) radiation or radiant energy. Electromagnetic radiation surrounds us! Natural sources of radiation from the sun, radioactive decay, and even the luminous glow from fireflies contribute to the electromagnetic radiation around us. Artificial sources such as radio and television, microwave radar detection systems, telephone signals, light bulbs, and medical equipment, are also contributors. We have learned a great deal about nature and the structure of the atom by monitoring radiation with microscopes, telescopes and other scientific equipment. The continuum of this radiation is known as the electromagnetic spectrum. It includes x-rays and gamma rays; ultra-violet, visible, and infrared light; microwaves and radiowaves. Human vision is limited to the very narrow band of visible light. Electromagnetic radiation can be described as a wave characterized by two interdependent variables: Frequency , ν (nu), is the number of waves passing a certain point per second. Frequency is measured in Hertz (Hz). 1 Hz = 1 cycle/sec. Wavelength , λ (lambda), is the distance between a point on one wave and the corresponding point on the next wave. Wavelength is measured in units of length, which are convenient for the type of radiation being considered. Radio waves are measured in meters (m). Visible and ultraviolet light are measured in nanometers. 1 nm = 10 -9 m.
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4/15/13 Lab 2 - Flame Tests www.webassign.net/ebooks/wsugencheml1/lab_2/manual.html 2/6 The product of these two variables is the distance the wave travels in a second and is a constant known as the speed of light, c , ( 1a ) c = λν = 3.0 × 10 8 m/s Thus, electromagnetic radiation with a high (large) frequency has a short (small) wavelength and vice versa. Frequency and wavelength are inversely proportional, as shown below in the rearrangements of equation 1a c = λ ν = 3.0 × 10 8 m/s : ( 1b ) c λ = ν ( 1c ) c ν = λ A third variable in the wave is the amplitude, the intensity of the radiation; for visible light, this is perceived as brightness. Therefore, if we look at a given shade of blue, it will always have the same frequency and wavelength, but can be of different amplitudes. Another descriptor for radiation is chromaticity. Light can be monochromatic (a single wavelength) or polychromatic (many wavelengths such as white light). Light can also be
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