Define or give examples for the following terms using words and equations as nec

Question

Define or give examples for the following terms using words and equations as necessary. If a symbol exists, write it along with metric units (kg, m, s, J, N, kJ, kPa, C, K, kmol, etc.). a) system b) closed system c) open system d) isolated system e) property f) intensive property g) extensive property h) energy i) internal energy j) potential energy k) kinetic energy l) pressure m) atmospheric pressure n) absolute pressure o) gage pressure p) temperature scales q) absolute temperature r) relative temperature s) density t) specific volume u) ideal gas equation of state v) equation of state for solids and liquids w) equilibrium x) state of a system y) state postulate z) process aa) cycle bb) quasi-equilibrium or reversible process

Explanation / Answer

Bar is the unit of pressure equal to 105 pascal. Barometer is a device that measures the atmospheric pressure; thus, the atmospheric pressure is often referred to as the barometric pressure. Boundary is the real or imaginary surface that separates the system from its surroundings. The boundary of a system can be fixed or movable. Bourdon tube named after the French inventor Eugene Bourdon, is a type of commonly used mechanical pressure measurement device which consists of a hollow metal tube bent like a hook whose end is closed and connected to a dial indicator needle. British thermal unit (Btu) is the energy unit in the English system needed to raise the temperature of 1 lbm of water at 68 °F by 1°F. Calorie (cal) is the amount of energy in the metric system needed to raise the temperature of 1 g of water at 15 °C by 1°C. Celsius scale (formerly called the centigrade scale; in 1948 it was renamed after the Swedish astronomer A. Celsius, 1701-1744, who devised it) is the temperature scale used in the SI system. On the Celsius scale, the ice and steam points are assigned the values of 0 and 100 °C, respectively. Chemical energy is the internal energy associated with the atomic bonds in a molecule. Chemical equilibrium is established in a system when its chemical composition does not change with time. Classical thermodynamics is the macroscopic approach to the study of thermodynamics that does not require knowledge of the behavior of individual particles. Closed system (also known as a control mass) consists of a fixed amount of mass, and no mass can cross its boundary. But energy, in the form of heat or work, can cross the boundary. Continuum is a view of mass as continuous, homogeneous matter with no holes. Matter is made up of atoms that are widely spaced in the gas phase. Yet it is very convenient to disregard the atomic nature of a substance. The continuum idealization allows us to treat properties as point functions, and to assume the properties to vary continually in space with no jump discontinuities. This idealization is valid as long as the size of the system we deal with is large relative to the space between the molecules. This is the case practically in all problems, except some specialized ones. Control surface is the boundary of a control volume, and it can be real or imaginary. Control volume, or open system is any arbitrary region in space through which mass and energy can pass across the boundary. Most control volumes have fixed boundaries and thus do not involve any moving boundaries. A control volume may also involve heat and work interactions just as a closed system, in addition to mass interaction. Cycle is a process, or series of processes, that allows a system to undergo state changes and returns the system to the initial state at the end of the process. That is, for a cycle the initial and final states are identical. Density is defined as mass per unit volume. Dimensionally homogeneous means that every term in an equation must have the same unit. To make sure that all terms in an engineering equation have the same units is the simplest error check one can perform. Dimensions are any physical characterizations of a quantity. English system which is also known as the United States Customary System (USCS), has the respective units the pound-mass (lbm), foot (ft), and second (s). The pound symbol lb is actually the abbreviation of libra, which was the ancient Roman unit of weight. Equilibrium implies a state of balance. In an equilibrium state there are no unbalanced potentials (or driving forces) within the system. A system in equilibrium experiences no changes when it is isolated from its surroundings. Extensive properties are those whose values depend on the size-or extent-of the system. Mass m, volume V, and total energy E are some examples of extensive properties. Fahrenheit scale (named after the German instrument maker G. Fahrenheit, 1686-1736) is the temperature scale in the English system. On the Fahrenheit scale, the ice and steam points are assigned 32 and 212 °F. Gage pressure is the difference between the absolute pressure and the local atmospheric pressure. Gravitational acceleration g is 9.807 m/s2 at sea level and varies by less than 1 percent up to 30,000 m. Therefore, g can be assumed to be constant at 9.81 m/s2. Ideal gas temperature scale is a temperature scale that turns out to be identical to the Kelvin scale. The temperatures on this scale are measured using a constant-volume gas thermometer, which is basically a rigid vessel filled with a gas, usually hydrogen or helium, at low pressure. Incompressible substances such as liquids and solids, have densities that have negligible variation with pressure. Independent properties exist when one property can be varied while another property is held constant. Intensive properties are those that are independent of the size of a system, such as temperature, pressure, and density. Internal energy U of a system is the sum of all the microscopic forms of energy. Iso prefix is often used to designate a process for which a particular property remains constant. Isobaric process is a process during which the pressure P remains constant. Isochoric (or isometric) process is a process during which the specific volume v remains constant. Isolated system is a closed system in which energy is not allowed to cross the boundary. Isothermal process is a process during which the temperature T remains constant. Joule (J) is a unit of energy and has the unit "newton-meter (N·m)." Kelvin scale is the thermodynamic temperature scale in the SI and is named after Lord Kelvin (1824-1907). The temperature unit on this scale is the kelvin, which is designated by K (not °K; the degree symbol was officially dropped from kelvin in 1967). The lowest temperature on the Kelvin scale is 0 K. Kilojoule (1 kJ) is 1000 joules. Kilopascal (kPa) is the unit of pressure equal to 1000 pascal or 1000 N/m2. Kinetic energy KE is energy that a system possesses as a result of its motion relative to some reference frame. When all parts of a system move with the same velocity, the kinetic energy is expressed as KE = m V2/2. Latent energy is the internal energy associated with the phase of a system. Macroscopic forms of energy are those a system possesses as a whole with respect to some outside reference frame, such as kinetic and potential energies. Manometer is a device based on the principle that an elevation change of ? z of a fluid corresponds to a pressure change of ?P/ ?g, which suggests that a fluid column can be used to measure pressure differences. The manometer is commonly used to measure small and moderate pressure differences. Mechanical equilibrium is related to pressure, and a system is in mechanical equilibrium if there is no change in pressure at any point of the system with time. Megapascal (MPa) is the unit of pressure equal to 106 pascal. Metric SI (from Le System International d' Unit), which is also known as the International System, is based on six fundamental dimensions. Their units, adopted in 1954 at the Tenth General Conference of Weights and Measures, are: meter (m) for length, kilogram (kg) for mass, second (s) for time, ampere (A) for electric current, degree Kelvin (K) for temperature, candela (cd) for luminous intensity (amount of light), and mole (mol) for the amount of matter. Microscopic forms of energy are those related to the molecular structure of a system and the degree of the molecular activity, and they are independent of outside reference frames. Newton (N) in SI, is the force unit defined as the force required to accelerate a mass of 1 kg at a rate of 1 m/s2.

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