![]() ![]() However, more complicated particle-size distributions describe the sizes of the particles in a polydisperse aerosol. Each distribution is normalized so that the total area is 1000.įor a monodisperse aerosol, a single number-the particle diameter-suffices to describe the size of the particles. diameter distribution, a surface area vs. The same hypothetical log-normal aerosol distribution plotted, from top to bottom, as a number vs. Also commonly used is the aerodynamic diameter, d a. The equivalent volume diameter ( d e) is defined as the diameter of a sphere of the same volume as that of the irregular particle. The equivalent diameter is the diameter of a spherical particle with the same value of some physical property as the irregular particle. Liquid droplets are almost always nearly spherical, but scientists use an equivalent diameter to characterize the properties of various shapes of solid particles, some very irregular. Most aerosols, however, as polydisperse colloidal systems, exhibit a range of particle sizes. A monodisperse aerosol, producible in the laboratory, contains particles of uniform size. Particle size has a major influence on particle properties, and the aerosol particle radius or diameter ( d p) is a key property used to characterise aerosols.Īerosols vary in their dispersity. Also commonly used is the number concentration ( N), the number of particles per unit volume, in units such as number per m 3 or number per cm 3. Environmental science and environmental health often use the mass concentration ( M), defined as the mass of particulate matter per unit volume, in units such as μg/m 3. There are several measures of aerosol concentration. ![]() Various types of aerosol, classified according to physical form and how they were generated, include dust, fume, mist, smoke and fog. Key aerosol groups include sulfates, organic carbon, black carbon, nitrates, mineral dust, and sea salt, they usually clump together to form a complex mixture. Primary aerosols contain particles introduced directly into the gas secondary aerosols form through gas-to-particle conversion. This term developed analogously to the term hydrosol, a colloid system with water as the dispersed medium. Donnan presumably first used the term aerosol during World War I to describe an aero- solution, clouds of microscopic particles in air. Meteorologists usually refer them as particle matter - PM2.5 or PM10, depending on their size. An aerosol includes both the particles and the suspending gas, which is usually air. Most of the particles in this aerosol are nearly spherical.Īerosol is defined as a suspension system of solid or liquid particles in a gas. Fill in the Blanks:The air is a _ of gases, dust particles, and water vapour.Photomicrograph made with a Scanning Electron Microscope (SEM): Fly ash particles at 2,000× magnification.The process of breakdown of food particles into small pieces is called (a) Mastication(b) Digestion(c) Peristalsis(d) Diffusion.Describe one example each of expansion in solids, liquids and gases.Out of solids, liquids, and gases, which one has :(a) maximum movement of particles?(b) maximum interparticle attractions?(c) minimum spaces between particles?.Name one property of liquids and gases which tells us that their molecules are moving constantly.When a beam of sunlight enters a room through a window, we can see tiny particles X suspended in a gas (or rather a mixture of gases) Y which are moving rapidly in a very haphazard manner.(a) What could particles X be?(b) Name the gas (or mixture of gases) Y.(c) What is the phenomenon exhibited by particles X known as?(d) What is causing the movement of particles X?(e) What conclusion does the existence of this phenomenon give us about the nature of matter?.Give one example of gas in a liquid solution.Give examples of osmosis and diffusion. ![]() This organism is:(a) Amoeba (b) Prawn (c) Planaria (d) Bryophyllum One of the following organism does not depend on simple diffusion of gases for breathing and respiration.All the gases from cathode rays and anode rays when electricity is passed through them :(i) What does the formation of cathode rays tell us about the atoms?(ii) What does the formation of anode rays tell us about the atoms?.Name an animal which depends on simple diffusion of gases for breathing.With the help of an example, explain how diffusion of gases in water is essential?.Give one example of the diffusion of a solid in another solid.Which one of the following sets of phenomena would increase on raising the temperature?(a) Diffusion, evaporation, compression of gases(b) Evaporation, compression of gases, solubility(c) Evaporation, diffusion, expansion of gases(d) Evaporation, solubility, diffusion, compression of gases. ![]()
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