أكاديميا - كولنز - معاجم الجيب العلمية - الفيزياء - انكليزي - فرنسي - عربي الحرف ٦_ s

Academia - Collins - Pocket Scientific Dictionaries - Physics - English - French - Arabic Letter 6_ S


standard temperature and pressure (STP)
Normal temperature and pressure

Standard temperature and pressure. Many values ​​of physical measurements depend on the temperature and pressure of the sample. Therefore, it is useful to state the value in terms of a clear set of conditions that should be easy to find anywhere in the world. The standard temperature and pressure are one of these groups: 0°C (the melting temperature of pure ice) and 101,325 Pascals (the standard air pressure).


standing waves
ondes fpl stationnaires

Stopped waves. Such a wave results from the interference of two similar waves of the same length in opposite directions in the same space. Stopped waves often appear when a progressive wave reverses back along its same path.
Adjacent points in a progressive wave have the same amplitude but differ in phase, and the opposite is true in the case of stopped waves.

All electromagnetic waves can generate standing waves, just as waves on the surface of water can. This relates to the action of all sound sources. Thus, when a person plucks a tight string, the string vibrates. A wave passes back and forth between the two ends of the string, and a stopped wave appears. The figure below shows the waves of a third overtone.
Also called stationary wave.


state
état mi

condition. Matter can exist in one of three states: solid, liquid, and gas. They vary greatly in their behavior. Using the kinetic model, we can describe the three states as different arrangements of matter particles. The pattern at a given moment depends on the material of the sample, its temperature and pressure. In a solid, Figure A below, the particles stick together in a fairly strong pattern. These particles have little energy, and their temperature is low. The particles vibrate about their average positions. Due to the low temperature, the evaporation rate is also low.

Figure (b) shows particles of a liquid sample. Particles are not fixed in place, but rather move around. This is what makes the liquid flowable. However, the forces between the particles remain strong, allowing only a few particles to escape from the surface. There is surface tension and little evaporation.

The gas or vapor particles, Figure (C) below, are almost completely free. It moves very quickly throughout the entire available space.

The state change includes latent energy because the transfer of energy is required to overcome the bonding forces between particles. See also plasma.

state change
change m d'état

Status change. Rearrangement of matter particles is necessary
To switch from one state to another. The table below shows the names of the state changes that can occur:

Solid -> Liquid: melting, melting.

Solid -> gaseous: sublimation, volatilization, (evaporation).

Liquid -> gaseous: boiling, volatilization, (evaporation).

Gaseous -> liquid: condensation, liquefaction.

Gaseous -> solid: sublimation, freezing.

Liquid -> solid: freezing, solidifying.

The change of state occurs for a pure substance with a specific pressure, always at the same temperature. This is not the case with evaporation, which is why this nomenclature is placed in parentheses above.) Impurities, as well as external pressure, affect the state change temperature. Thus, the liquid boils at a higher temperature if there is a substance dissolved in it, and if the pressure is higher than normal.
(See pressure cooker)
At most temperature/pressure states a substance can only exist in one state. The graph below shows the cases in which a state change can occur.
P (shown in the drawing) represents the triple point, that is, the only combination of temperature/pressure in which a solid, liquid, or gaseous substance can exist in a state of equilibrium, and the triple point of water is equal to 0.01°C.