这关键区别在熔点和冰点之间melting point is the temperature at which a solid will go to the liquid state whereas freezing point is the point at which any liquid will change its state to a solid。
相变是涉及能量释放或能量增益的过程。熔点和冰点是发生相变的点。有了这些,材料的许多其他特性也可能会改变。从理论上讲,材料的冰点和熔点是相同的,但有时对于特定物质,两个值彼此不同。
CONTENTS
1。概述和关键差异
2。什么是熔点
3。什么是冰点
4。并排比较 - 熔点与表格形式的冰点
5。Summary
什么是熔点?
Melting point is the temperature at which a solid will change into its liquid state. It is a physical property we can use to identify a compound. When a solid converts into a liquid stage, a phase change occurs. It occurs at a characteristic temperature for a given pressure. For this, we need to supply the required energy.
从固体到液体时,相变为吸收能量/热(吸热)。大多数情况下,这种能量是以热的形式提供的。需要加热以将固体的温度提高到其熔点状态。此外,该物质需要能量融化。我们称这种融合的能量热;这是一种潜热。
潜热是在相变时从物质中吸收或释放的热量。这些热变化不会导致温度变化,因为它们被吸收或释放。因此,在熔点,该物质会吸收热量,但温度不会相应变化。在热力学上,在熔点变化Gibbs free energy为零。以下方程对于在熔点处的材料有效。它表明温度不会改变,但是焓and熵物质变化。
ΔS=ΔH/t
由于该物质吸收了能量,因此焓在熔点增加。在固态下,颗粒的排序良好,运动较少。但是在液态下,它们的随机性质增加。因此,在熔点,熵增加。根据压力,给定材料有一个特定的熔点。我们只能确定固体的熔点。
In the laboratory, we can use many techniques to determine the melting point. Using a melting point apparatus is very easy. We can put some finely powdered solid into a capillary in which one end is sealed. Then we should put the sealed end that contains the solid into the apparatus. Here, the end should touch the metal inside. Thereafter, we can observe the solid through the magnifying glass window of the apparatus. There is also a thermometer to record the temperature. When temperature gradually increases, the metal will heat and, the solid in the capillary will also heat. We can observe the point at which the melting starts and finishes. And, this range corresponds to the melting point. The melting point of water is 0 °C. Tungsten has the highest melting point, which is 3410 °C.
什么是冰点?
冰点是任何液体将其状态变为固体的温度。材料的熔点温度和冰点的温度或多或少是相同的值。例如,水在0°C下变成冰,其熔点也为0°C。更确切地说,冰点描述了物质相的变化。
此外,冻结物质的过程减少了熵。化学中有一个术语为“冰点抑郁症”,该术语解释了溶液中非易失性溶质的存在如何降低溶剂的冰点温度。
熔点和冰点有什么区别?
熔点和冰点是相同相变的相反方向。熔点和冰点之间的关键区别在于,熔点是固体进入液态的温度,而冰点是任何液体将其状态变为固体的点。此外,熔点和冰点之间的熵变化之间也有所不同。在熔化固体的同时,熵增加,但在冷冻中,熵减少。此外,尽管从理论上讲,给定材料的熔点和冰点温度相似,但实际上它们略有不同。
摘要 - 熔点与冰点
熔点和凝固点是两个物理properties of substances. The key difference between melting point and freezing point is that melting point is the temperature at which a solid will go to the liquid state whereas freezing point is the point where any liquid will change its state to a solid.
参考:
1. Helmenstine,Anne Marie博士“水的冰点是什么?”ThinkCo,2018年10月5日,在这里可用。
图片提供:
1. Albris的“元素的熔点(k)” - 自己的作品(CC BY-SA 4.0)通过下议院维基梅迪亚
2.“ 1550739”(CC0)通过pxhere
S DGsays
有用的信息