density (redirected from density sampling)

density, ratio of the mass of a substance to its volume, expressed, for example, in units of grams per cubic centimeter or pounds per cubic foot. The density of a pure substance varies little from sample to sample and is often considered a characteristic property of the substance. Most substances undergo expansion when heated and therefore have lower densities at higher temperatures. Many substances, especially gases, can be compressed into a smaller volume by increasing the pressure acting on them. For these reasons, the temperature and pressure at which the density of a substance is measured are usually specified. The density of a gas is often converted mathematically to what it would be at a standard temperature and pressure (see STP). Water is unusual in that it expands, and thus decreases in density, as it is cooled below 3.98°C; (its temperature of maximum density). Density often is taken as an indication of how "heavy" a substance is. Iron is denser than cork, since a given volume of iron is more massive (and weighs more) than the same volume of cork. It is often said that iron is "heavier" than cork, although a large volume of cork obviously can be more massive and thus be heavier (i.e., weigh more) than a small volume of iron. See specific gravity.

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density

Mass of a unit volume of a material substance. It is calculated by dividing an object's mass by its volume. In the International System of Units, and depending on the units of measurement used, density can be expressed in grams per cubic centimetre (g/cm³) or kilograms per cubic metre (kg/m³). The expression “particle density” refers to the number of particles per unit volume, not to the density of a single particle. See also specific gravity.

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density

See packing density and bit density.

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density

1. a measure of the compactness of a substance, expressed as its mass per unit volume. It is measured in kilograms per cubic metre or pounds per cubic foot.

2. a measure of a physical quantity per unit of length, area, or volume

3. Physics Photog See transmission density reflection density

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density [′den· səd·ē]

(materials)

Closeness of texture or consistency.

(mathematics)

For an increasing sequence of integers, the greatest lower bound of the quantityF(n)/n,whereF(n) is the number of integers in the sequence (other than zero) equal to or less thann.

(mechanics)

The mass of a given substance per unit volume.

(optics)

The degree of opacity of a translucent material.

The common logarithm of opacity.

(physics)

The total amount of a quantity, such as energy, per unit of space.

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Density

The mass per unit volume of a material. The term is applicable to mixtures and pure substances and to matter in the solid, liquid, gaseous, or plasma state. Density of all matter depends on temperature; the density of a mixture may depend on its composition, and the density of a gas on its pressure. Common units of density are grams per cubic centimeter, and slugs or pounds per cubic foot. The specific gravity of a material is defined as the ratio of its density to the density of some standard material, such as water at a specified temperature, for example, 60°F (15.6°C), or, for gases the basis may be air at standard temperature and pressure. Another related concept is weight density, which is defined as the weight of a unit volume of the material. See Mass, Weight