chapter 7- mastering chemistry Flashcards
what does it mean for a particle to be absolutely small? what particles fit this description?
When a particle is absolutely small it means that you cannot observe it without disturbing it. When you observe the particle, it behaves differently than when you do not observe it. Electrons fit this description.
why is the quantum- mechanical model of the atom important for understanding chemistry?
The quantum-mechanical model of the atom is important because it explains how electrons exist in atoms and how those electrons determine the chemical and physical properties of elements.
define the wavelength and amplitude of a wave. how are these related to the energy of the wave?
The wavelength (λ) of the wave is the distance in space between adjacent crests and is
measured in units of distance. The amplitude of the wave is the vertical height of a crest. The more closely spaced the waves, that is, the shorter the wavelength, the more energy there is. The amplitude of the electric and magnetic field waves in light determines the intensity or brightness of the light. The higher the amplitude, the greater the energy of the wave.
what determines the colour of light? for example, describe the difference between red light and blue light?
For visible light, wavelength determines the colour. Red light has a wavelength of 750 nm, the longest wavelength of visible light, and blue has a wavelength of 500 nm
give an approximate range of wavelengths for each type of electromagnetic radiation and summarize the characteristics and/ or uses of gamma rays
Gamma rays (γ) – the wavelength range is 10−11 to 10−15 m. Gamma rays are produced by the sun, other stars, and certain unstable atomic nuclei on Earth. Human exposure to gamma rays is dangerous because the high energy of gamma rays can damage biological
molecules.
give an approximate range of wavelengths for each type of electromagnetic radiation and summarize the characteristics and/ or uses of x rays
(b) X-rays – the wavelength range is 10−8 to 10−11 m. X-rays are used in medicine. X-rays pass through many substances that block visible light and are therefore used to image bones and internal organs. X-rays are sufficiently energetic to damage biological mol- ecules so, while several yearly exposures to X-rays are harmless, excessive exposure increases cancer risk.
give an approximate range of wavelengths for each type of electromagnetic radiation and summarize the characteristics and/ or uses of ultraviolet radiation(UV)
(c) Ultraviolet radiation (UV) – the wavelength range is 0.4 10−6 to 10−8 m. Ultraviolet radi- ation is most familiar as the component of sunlight that produces a sunburn or suntan. While not as energetic as gamma rays or X-rays, ultraviolet light still carries enough energy to damage biological molecules. Excessive exposure to ultraviolet light increases the risk of skin cancer and cataracts and causes premature wrinkling of the skin.
give an approximate range of wavelengths for each type of electromagnetic radiation and summarize the characteristics and/ or uses of visible light
(d) Visible light – the wavelength range is 0.75 10−6 to 0.4 10−6 m (750 nm to 400 nm). Visible light, as long as the intensity is not too high, does not carry enough energy to damage biological molecules. It does, however, cause certain molecules in our eyes to change their shape, sending a signal to the brain that results in vision.
give an approximate range of wavelengths for each type of electromagnetic radiation and summarize the characteristics and/ or uses of infrared radiation (IR)
(e) Infrared radiation (IR) – the wavelength range is 0.75 10−6 to 10−3 m. The heat you feel when you place your hand near a hot object is infrared radiation. All warm objects, including human bodies, emit infrared light. Although infrared light is invisible to our eyes, infrared sensors can detect it and are often used in night vision technology to “see” in the dark.
give an approximate range of wavelengths for each type of electromagnetic radiation and summarize the characteristics and/ or uses of microwave radiation
(f) Microwave radiation – the wavelength range is 10−3 to 10−1 m. Microwave radiation is used in radar and in microwave ovens. Microwave radiation is efficiently absorbed by water and can therefore heat substances that contain water.
give an approximate range of wavelengths for each type of electromagnetic radiation and summarize the characteristics and/ or uses of radio waves
(g) Radio waves – the wavelength range is 10−1 to 105 m. Radio waves are used to transmit the signals responsible for AM and FM radio, cellular telephones, television, and other forms of communication.
explain the wave behavior known as diffraction
Diffraction occurs when a wave encounters an obstacle or a slit that is comparable in size to its wave- length. The wave bends around the slit. The diffraction of light through two slits separated by a distance comparable to the wavelength of the light results in an interference pattern. Each slit acts as a new wave source, and the two new waves interfere with each other. This results in a pattern of bright and dark lines.
how did the photoelectric effect lead einstein to propose that light is quantized?
Because of the results of the experiments with the photoelectric effect, Einstein proposed that light energy must come in packets. The amount of energy in a light packet depends on its frequency (wavelength). The emission of electrons depends on whether or not a single photon has sufficient energy to dislodge a single electron.
