Properties intensive property

Some properties of a sample of a substance depend on the quantity of the sample. These properties are called extensive properties. For example, the weight of a solid sample depends on how much of the substance is present. Other properties, such as color and taste, do not depend on how much is present. These properties are known as intensive properties. Intensive properties are much more useful for identifying substances. 

Define or explain the following terms energy, system, closed system, nonflow system, open system, flow system, surroundings, property, extensive property, intensive property, state, heat, work, kinetic energy, potential energy, internal energy, enthalpy, initial state, final state, point (state) function, state variable, cyclical process, and path function. 

The balance equation cannot be applied to uncountable individuals (units) or to intensive properties. Intensive properties are independent of the amount of matter present. Some examples are temperature, pressure, viscosity, hardness, color, honesty, electric voltage, beauty, and density. An example of uncountable individuals is all the decimal fractions between 0 and 1. 

Some properties, such as temperature and melting point, are intensive properties. Intensive properties do not depend on the amount of sample being examined and are particularly useful in chemistry because many intensive properties can be used to identify substances. Extensive properties depend on the amount of sample, with two examples being mass and volume. Extensive properties relate to the amount of substance present. 

Some physical properties are extensive properties, properties that depend on the amount of matter present. Mass and volume are extensive properties. Intensive properties, however, don t depend on the amount of matter present. Color is an intensive property. A large chunk of gold, for example, is the same color as a small chunk of gold. The mass and volume of these two chunks are different (extensive properties), but the color is the same. Intensive properties are especially useful to chemists because they can use intensive properties to identify a substance. 

A characteristic of a system is called a property. Intensive properties do not directly depend on the amount of matter in the system (for example temperature and pressure). Extensive properties, for example mass and volume, do directly depend on the number of particles. The ratio of two extensive properties becomes intensive in nature. 

Equation (A2.1.23) can be mtegrated by the following trick One keeps T, p, and all the chemical potentials p. constant and increases the number of moles n. of each species by an amount n. d where d is the same fractional increment for each. Obviously one is increasing the size of the system by a factor (1 + dQ, increasing all the extensive properties U, S, V, nl) by this factor and leaving the relative compositions (as measured by the mole fractions) and all other intensive properties unchanged. Therefore, d.S =. S d, V=V d, dn. = n. d, etc, and... 

Determination of purity. The ultraviolet and visible absorption is often a fairly intensive property thus e values of high intensity bands may be of the order of 10 -10 . In infrared spectra e values rarely exceed 10 . It is therefore often easy to pick out a characteristic band of a substance present in small concentration in admixture with other materials. Thus small amounts of aromatic compounds can be detected in hexane or in cyclohexane. 

QSPR methods have yielded the most accurate results. Most often, they use large expansions of parameters obtainable from semiempirical calculations along with other less computationally intensive properties. This is often the method of choice for small molecules. 

In addition to total energy and gradient, HyperChem can use quantum mechanical methods to calculate several other properties. The properties include the dipole moment, total electron density, total spin density, electrostatic potential, heats of formation, orbital energy levels, vibrational normal modes and frequencies, infrared spectrum intensities, and ultraviolet-visible spectrum frequencies and intensities. The HyperChem log file includes energy, gradient, and dipole values, while HIN files store atomic charge values. 

Because the macroscopic-intensive properties of homogeneous fluids in equilibrium states ate functions of T, P, and composition, it follows that the total property of a phase fiM can be expressed functionally as in equation 113 ... 

The phase rule specifies the number of intensive properties of a system that must be set to estabUsh all other intensive properties at fixed values (3), without providing information about how to calculate values for these properties. The field of appHed engineering thermodynamics has grown out of the need to assign numerical values to thermodynamic properties within the constraints of the phase rule and fundamental laws. In the engineering disciplines there is a particular demand for physical properties, both for pure fluids and mixtures, and for phase equiUbrium data (4,5). 

The term ff denotes the number of independent phase variables that should be specified in order to establish all of the intensive properties of each phase present. The phase variables refer to the intensive properties of the system such as temperature (T), pressure (P), composition of the mixture (e.g., mole fractions, x ), etc. As an example, consider the triple point of water at which all three phases—ice, liquid water, and water vapor—coexist in equilibrium. According to the phase rule,... 

The origin of this rule lies in the expression for the specific volume of the wet vapor, V = qV + (1 - q)V,. The specific intensive properties of the wet vapor are obtained readily from the individual properties of its component phases by an analogous equation ... 

Properties of gold. The color of gold is an intensive property. The quantity of gold in a sample is an extensive property. The fact that gold can be stored in the air without undergoing any chemical reaction with oxygen in the air is a chemical property. The temperature at which gold melts (1063°C) is a physical property. 

Specific heat, like density or melting point, is an intensive property that can be used to identify a substance or determine its purity. Water has an unusually large specific heat,... 

The driving force behind the spontaneous reaction in a voltaic cell is measured by the cell voltage, which is an intensive property, independent of the number of electrons passing through the cell. Cell voltage depends on the nature of the redox reaction and the concentrations of the species involved for the moment, we ll concentrate on the first of these factors. 

An alternative is to consider the value of the thermodynamic property per unit mass. Such quantities are called specific properties. Thus the specific volume is the volume per unit mass. It is the reciprocal of the density and is an intensive property. 

Properties are also classified according to their dependence on the mass of a sample. An intensive property is a property that is independent of the mass of the sample. For example, temperature is an intensive property, because we could take a sample of any size from a uniform bath of water and measure the same temperature (Fig. A.2). An extensive property is a property that does depend on the mass ( extent ) of the sample. Volume is an extensive property 2 kg of water occupies twice the volume of 1 kg of water. 

Some intensive properties are ratios of two extensive properties. For example, the property density, d, mentioned above, is a ratio of the mass, m, of a sample divided by its volume, V ... 

The density of a substance is independent of the size of the sample because doubling the volume also doubles the mass so the ratio of mass to volume remains the same. Density is therefore an intensive property. We distinguish different substances by their intensive properties. Thus, we might recognize a sample as water by noting its color, density (1.00 g-cm-3), melting point (0°C), boiling point (100°C), and the fact that it is a liquid. 

Physical properties are those that do not involve changing the identity of a substance. Chemical properties are those that involve changing the identity of a substance. Extensive properties depend on the mass of the sample intensive properties do not. The precision of a measurement controls the number of significant figures that are justified by the procedure the accuracy of a measurement is its closeness to the true value. 

Because the mass percentage composition is independent of the size of the sample— in the language of Section A, it is an intensive property—every sample of the substance has that same composition. A principal technique for determining the mass percentage composition of an unknown organic compound is combustion analysis. Chemists commonly send samples to a laboratory or agency for combustion analysis and receive the results as mass percentage composition (see Section M). 

The best way to determine the type of unit cell adopted by a metal is x-ray diffraction, which gives a characteristic diffraction pattern for each type of unit cell (see Major Technique 3 following his chapter). However, a simpler procedure that can be used to distinguish between close-packed and other structures is to measure the density of the metal we then calculate the densities of the candidate unit cells and decide which structure accounts for the observed density. Density is an intensive property, which means that it does not depend on the size of the sample (Section A). Therefore, it is the same for a unit cell and a bulk sample. Hexagonal and cubic close packing cannot be distinguished in this way, because they have the same coordination numbers and therefore the same densities (for a given element). 

The intensive property that determines the direction in which heat will flow between two objects in contact. 

Unlike mass and volume, density does not vary with the amount of a substance. Notice in Figure 1-20 that all the corks float, regardless of their sizes. Notice also that all the pieces of lead sink, regardless of their sizes. Dividing a sample into portions changes the mass and volume of each portion but leaves the density unchanged. A property that depends on amount is called extensive. Mass and volume are two examples of extensive properties. A property that is independent of amount is called intensive. Density and temperature are intensive properties. 

The state (or behaviour) of a system is described by variables or properties which may be classified as (a) extensive properties such as mass, volume, kinetic energy and (b) intensive properties which are independent of system size, e.g., pressure, temperature, concentration. An extensive property can be treated like an intensive property by specifying that it refers to a unit amount of the substance concerned. Thus, mass and volume are extensive properties, but density, which is mass per unit volume, and specific volume, which is volume per unit mass, are intensive properties. In a similar way, specific heat is an intensive property, whereas heat capacity is an extensive property. 

The chemical potentials sought are intensive properties of the system, in the usual thermodynamic language [26]. Furthermore, AUa is a quantity of molecular order of magnitude. Specifically, the AUa defined by (9.13) should be system-size independent for typical configurations of thermodynamically large systems. Because of... 

We can express the use of all the different units in evolution in the language of thermodynamics. While the genome is defined by a DNA sequence so that each base has a singular intensive property as in a computer code of symbols, by way of contrast, the protein content of a cell is an extensive property being concentration dependent and therefore varies under circumstances such as temperature and pressure although... 

This relationship is expressed in extensive properties that depend on the extent of the system, as opposed to intensive properties that describe conditions at a point in the system. For example, extensive properties are made intensive by expressing them on a per unit mass basis, e.g. s = S/m density, p 1 /v, v V/m. For a pure system (one species), Equation (1.2) in intensive form allows a definition of thermodynamic temperature and pressure in terms of the intensive properties as... 

The thermodynamic pressure is equal to the mechanical pressure due to force at equilibrium. While most problems of interest possess gradients in the intensive properties... 

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