| 释义 |
melting point
melt·ing point (mĕl′tĭng)n. Abbr. mp1. The temperature at which a solid becomes a liquid at a fixed pressure, usually standard pressure.2. The temperature at which a solid and its liquid are in equilibrium, at any fixed pressure.melting point n (Chemistry) the temperature at which a solid turns into a liquid. It is equal to the freezing point melt′ing point`
n. the temperature at which a solid substance melts or fuses. [1835–45] melt·ing point (mĕl′tĭng) The temperature at which a solid becomes a liquid. For a given substance, the melting point of its solid form is the same as the freezing point of its liquid form. The melting point of ice is 32°F (0°C); that of iron is 2,797°F (1,535°C).Thesaurus| Noun | 1. |  melting point - the temperature below which a liquid turns into a solidfreezing pointtemperature - the degree of hotness or coldness of a body or environment (corresponding to its molecular activity) |
Translationspunto di fusionesmeltepunktmelting point
melting point, temperaturetemperature,
measure of the relative warmth or coolness of an object. Temperature is measured by means of a thermometer or other instrument having a scale calibrated in units called degrees. The size of a degree depends on the particular temperature scale being used.
..... Click the link for more information. at which a substance changes its state from solid to liquid. Under standard atmospheric pressure different pure crystalline solids will each melt at a different specific temperature; thus melting point is a characteristic of a substance and can be used to identify it. When heat is applied continuously and in sufficient quantity to such solids, the temperature rises steadily until it reaches the point at which liquefaction occurs. Here the rise ceases and no further change in temperature is observed until all of the substance has been converted to liquid. The heat being applied to the substance at that temperature is consumed in bringing about the change of state, and none is available to raise the temperature of that part of the substance already liquefied until all of it has changed to the liquid. If heat is still applied when liquefaction is complete, the temperature will begin to rise again. The quantity of heat necessary to change one gram of any substance from solid to liquid at its melting point is known as its latent heatlatent heat,
heat change associated with a change of state or phase (see states of matter). Latent heat, also called heat of transformation, is the heat given up or absorbed by a unit mass of a substance as it changes from a solid to a liquid, from a liquid to a gas, or the
..... Click the link for more information. of fusion and differs for different substances. Ice, for example, requires approximately 80 calories of heat to change each gram to water at its melting point. Because its heat of fusion is relatively high, ice is used in refrigeration. In freezing (the reverse process, i.e., the change from liquid to solid), heat is given off by the substance undergoing the change, and the amount given off is the same as that absorbed in melting.Melting Point (mp), the temperature of the equilibrium phase transition of a crystalline (solid) body to liquid at a constant external pressure. The melting point is a particular case of the temperature of the first-order phase transition. The melting points of several substances at standard pressure (760 mm Hg, or 101,325 newtons per m2) are shown in Table 1. | Table 1 |
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| Substance | mp (°C) |
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| Hydrogen ............... | –259.14 | | Oxygen ............... | –218.4 | | Nitrogen ............... | – 209.86 | | Argon ............... | –189.2 | | Ethyl alcohol ............... | –112.0 | | Methyl alcohol ............... | –97.8 | | Acetone ............... | –94.6 | | Mercury ............... | –38.9 | | Ethylone glycol ............... | –15.6 | | Nitrobenzene ............... | 5.7 | | Acetic acid ............... | 16.7 | | Glycerine ............... | 17.9 | | Cesium ............... | 28.5 | | Naphthalene ............... | 80.2 | | Sodium ............... | 97.8 | | Iodine ............... | 112.9 | | D-Camphor ............... | 178.5 | | Aluminum ............... | 660.37 | | Copper ............... | 1083.4 | | Iron ............... | 1539.0 | | Tungsten ............... | 3410.0 |
melting point[′melt·iŋ ‚pȯint] (thermodynamics) The temperature at which a solid of a pure substance changes to a liquid. Abbreviated mp. For a solution of two or more components, the temperature at which the first trace of liquid appears as the solution is heated. melting point the temperature at which a solid turns into a liquid. It is equal to the freezing point melting point
point [point] 1. a small area or spot; the sharp end of an object.2. to approach the surface, like the pus of an abscess, at a definite spot or place.3. a tapered, pointed endodontic instrument used for exploring the depth of the root canal in therapy" >root canal therapy; called also root canal point.point A a radiographic, cephalometric landmark, determined on the lateral head film; it is the most retruded part of the curved bony outline from the anterior nasal spine to the crest of the maxillary alveolar process.absorbent point in root canal therapy, a cone of variable width and taper, usually made of paper or a paper product, used to dry or maintain a liquid disinfectant in the canal. Called also paper point.point B a radiographic, cephalometric landmark, determined on the lateral head film; it is the most posterior midline point in the concavity between the infradentale and pogonion.boiling point the temperature at which a liquid will boil; at sea level the boiling point of water is 100°C (212°F).cardinal p's 1. the points on the different refracting media of the eye that determine the direction of the entering or emerging light rays.2. four points within the pelvic inlet— the two sacroiliac articulations and the two iliopectineal eminences.craniometric p's the established points of reference for measurement of the skull.dew point the temperature at which moisture in the atmosphere is deposited as dew.far point the most remote point at which an object is clearly seen when the eye is at rest.point of fixation 1. the point or object on which one's sight is fixed and through which the axis opticus passes.2. the point on the retina, usually the fovea, on which are focused the rays coming from an object directly regarded.freezing point the temperature at which a liquid begins to freeze, for water, 0°C (32°F); it is often used interchangeably with point" >melting point, but should be used for substances being cooled while melting point is reserved for substances being heated.gutta-percha point gutta-percha cone.ice point the true melting point of ice, being the temperature of equilibrium between ice and air-saturated water under one atmosphere pressure.isoelectric point (pI) the pH of a solution in which molecules of a specific substance, such as a protein, have equal numbers of positively and negatively charged groups and therefore do not migrate in an electric field.J point on an electrocardiogram, the junction between the end of the QRS segment and the beginning of the ST segment.jugal point the point at the angle formed by the masseteric and maxillary edges of the zygomatic bone; called also jugale.lacrimal point a small aperture on a slight elevation at the medial end of the eyelid margin, through which tears from the lacrimal lake enter the lacrimal canaliculi. See also lacrimal apparatus.point of maximal impulse the point on the chest where the impulse of the left ventricle is sometimes felt or seen most strongly, normally in the fifth costal interspace inside the mammillary line.McBurney point a point of special tenderness in appendicitis, about 4 to 5 cm from the right anterior iliac spine on a line between the spine and the navel; it corresponds to the normal position of the appendix.  McBurney's point is located midway between the anterior iliac crest and the umbilicus in the right lower quadrant. From Ignatavicius and Workman, 2002.melting point (mp) the minimum temperature at which a solid begins to liquefy; see also point" >freezing point.near point the nearest point of clear vision, the absolute near point being that for either eye alone with accommodation relaxed, and the relative near point being that for the two eyes together with employment of accommodation.nodal p's two points on the axis of an optical system situated so that a ray falling on one will produce a parallel ray emerging through the other.paper point absorbent point.pressure point 1. a point of extreme sensitivity to pressure.2. one of various locations on the body at which digital pressure may be applied for the control of hemorrhage.  Locations of pressure points. Shaded areas show the regions in which hemorrhage may be controlled by pressure at the points indicated.root canal point point (def. 3).silver point in therapy" >root canal therapy, a tapered and elongated silver plug that is cemented into the canal as a filling. Called also silver cone.trigger point a spot on the body at which pressure or other stimulus gives rise to specific sensations or symptoms.triple point the temperature and pressure at which the solid, liquid, and gas phases of a substance are in equilibrium.melt·ing point (m.p., Tm), 1. the temperature at which a solid becomes a liquid; 2. the temperature at which 50% of a macromolecule becomes denatured. melt·ing point (melt'ing poynt) 1. The temperature at which a solid becomes a liquid. 2. The temperature at which 50% of a macromolecule becomes denatured. melting point the temperature at which a solid liquefies.FinancialSeePointSee MP
See MLTmelting point
Synonyms for melting pointnoun the temperature below which a liquid turns into a solidSynonymsRelated Words |