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  • 超饱和溶液

    A person applies a thermal pack to another's back, showcasing its use for heat therapy.

    How does a hot or a cold pack work?
    ::热的还是冷的怎么用?

    In the picture above, a thermal pack is applied to the back. Small packs can be used either for heating or cooling, depending on the material used. A pack contains a supersaturated solution of material such as sodium acetate. The solution is clear until a small metal trigger is activated. The sodium acetate then crystallizes out of solution and generates heat in the process.
    ::在上图中,对背部应用了热包,小包可用作取暖或冷却,视所用材料而定。一个包含有乙酸钠等材料的超饱和溶液。溶液在小金属触发器启动前是清楚的。然后,乙酸钠在溶液中结晶,并在过程中产生热。

    Supersaturated Solutions
    ::超饱和溶液

    Some solutes, such as sodium acetate, do not recrystallize easily. Suppose an exactly saturated solution of sodium acetate is prepared at 50°C. As it cools back to room temperature , no crystals appear in the solution, even though the of sodium acetate is lower at room temperature. A supersaturated solution is a solution that contains more dissolved solute than the maximum amount of solute that is capable of being dissolved at a given temperature. The recrystallization of the excess dissolved solute in a supersaturated solution can be initiated by the addition of a tiny crystal of solute, called a seed crystal. The seed crystal provides a nucleation site on which the excess dissolved crystals can begin to grow. Recrystallization from a supersaturated solution is typically very fast. 
    ::一些溶液,如乙酸钠,不会轻易地内吸。假设在50°C时准备了完全饱和的乙酸钠溶液。当溶液冷却回到室温时,溶液中不会出现晶体,即使乙酸钠在室温下较低。超饱和溶液是一种溶液,溶液中溶解溶液的溶液含量大于在特定温度下溶解溶解溶液的最大量。在超饱和溶液中,超溶溶溶溶溶溶溶溶液溶解溶解溶液的内吸剂的硬化可以通过添加一种叫做种子晶的微溶液来启动。种子晶提供了一个核分离点,使超溶解晶能够开始生长。从超饱和溶液中再溶解溶解的溶液通常非常快。

    This video shows the rapid recrystallization that occurs when a supersaturated sodium acetate solution is poured on to a sodium acetate seed crystal:
    ::本视频显示当将超饱和乙酸钠溶液倒入乙酸钠种子晶体时发生的快速内晶反应:

     

    Supersaturated solutions can be used to make candy. See if you control certain variables to make the most candy in this simulation: 
    ::超饱和性溶液可用于制作糖果。 查看您是否控制某些变量来制作此模拟中最多的糖果 :

    Summary
    ::摘要

    • A supersaturated solution is a solution that contains more dissolved solute than the maximum amount of solute that is capable of being dissolved at a given temperature.
      ::超饱和溶液是一种溶液,溶液中溶解溶液的溶液含量大于在特定温度下溶解的溶液的最大溶液含量。
    • A supersaturated solution can recrystallize when a seed crystal is added to the solution.
      ::当将种子晶体添加到溶液中时,超饱和溶液可再次内吸。

    Review
    ::回顾

    1. How do we know a solution is supersaturated?
      ::我们怎么知道一个解决方案是超饱和的?
    2. How can we cause recrystallization of a supersaturated solution?
      ::我们怎样才能造成超饱和溶液的内晶化?
    3. What does the seed crystal do?
      ::种子晶是做什么的?