The temperature, defined as 0K on the Kelvin scale, at which the motion of molecules in a solid virtually ceases. Absolute zero is equal to −459.67°F (−273.15°C).
The smallest particle of a chemical element. An atom can exist either alone or in combination with other atoms in a molecule.
The constant but irregular zigzagging of colloidal particles, which can be seen clearly through amicroscope. The phenomenon is Named after Scottish botanist Robert Brown (1773-1858), who first witnessed it but was not able to explain it. The behavior exhibited in Brownian motion provides evidence for the kinetic theory of matter.
The transition from one phase of matter to another.
A substance made up of atoms of more than one chemical element. These atoms are usually joined in molecules.
A substance made up of only one kind of atom.
A pattern that occurs when particles of one substance are dispersed—but not dissolved—in another substance. A puff of smoke in the air is an example of acolloid, whose behavior is typically characterized by Brownian motion.
A coordinate, plotted on a phase diagram, above which a substance cannot exist in anything other than the gaseous state. Located at a position of very high temperature and pressure, the critical point marks the termination of the vaporization curve.
The study of why objects move as they do. Dynamics is an element of mechanics.
Any substance, whether gas or liquid, which tends to flow, and which conforms to the shape of its container. Unlike solids, fluids are typically uniform in molecular structure: for instance, one molecule of water is the same as another water molecule.
The boundary between solid and liquid for any given substance, as plotted on a phase diagram.
A phase of matter in which molecules exert little or no attraction toward one another, and, therefore, move at high speeds.
Internal thermal energy that flows from one body of matter to another.
Established by William Thomson, Lord Kelvin (1824-1907), the Kelvin scale measures temperature in relation to absolute zero, or 0K.(Units in the Kelvin system, known as Kelvins, do not include the word or symbol for degree.) The Kelvin and Celsius scales are directly related; hence, Celsius temperatures can be converted to Kelvins by adding 273.15.
The energy that an object possesses by virtue of its motion.
The idea that a gas consists of numerous molecules, relatively far apart in space, which interact by colliding. These collisions are responsible for the production of thermal energy, because when the velocity of the molecules increases—as it does after collision—the temperature increases as well.
The application of the kinetic theory of gases to all forms of matter. Since particles of liquids and solids move much more slowly than do gas particles, kinetic theory is not as successful in this regard; however, the proposition that the internal energy of any substance is at least partly related to the kinetic energies of its molecules helps explain much about the behavior of matter.
A phase of matter in which molecules exert moderate attractions toward one another, and, therefore, move at moderate speeds.
Physical substance that has mass; occupies space; is composed of atoms; and is ultimately convertible to energy. There are several phases of matter, including solids, liquids, and gases.
The study of bodies in motion.
A unit equal to 6.022137 × 10 23 (more than 600 billion trillion) molecules. Since their size makes it impossible to weigh molecules in relatively small quantities; hence, the mole, devised by Italian physicist Amedeo Avogadro (1776-1856), facilitates comparisons of mass betweensubstances.
The study and simulation of molecular motion.
A group of atoms, usually of more than one chemical element, joined in a structure.
A chart, plotted for any particular substance, identifying the particular phase of matter for that substance at a given temperature and pressure level. A phase diagram usually shows temperature along the x-axis, and pressure along the y-axis.
The various forms of material substance (matter), which are defined primarily in terms of the behavior exhibited by their atomic or molecular structures. On Earth, three principal phases of matter exist, namely solid, liquid, and gas.
The energy an object possesses by virtue of its position.
A phase of matter in which molecules exert strong attractions toward one another, and, therefore, move slowly.
A realm of the physical sciences devoted to the study of large systems by examining the behavior of their smallest parts.
The boundary between solid and gas for any given substance, as plotted on a phase diagram.
In physics, the term "system" usually refers to any set of physical interactions isolated from the rest of the universe. Anything outside of the system, including all factors and forces irrelevant to a discussion of that system, is known as the environment.
A measure of the average kinetic energy—or molecular translational energy in a system. Differences in temperature determine the direction of internal energy flow between two systems when heat is being transferred.
Heat energy, a form of kinetic energy produced by the movement of atomic or molecular particles. The greater the movement of the separticles, the greater the thermal energy.
The study of the relationships between heat, work, and energy.
The boundary between liquid and gas for any given substance as plotted on a phase diagram.
Comment about this article, ask questions, or add new information about this topic: