Name: suspensions, sedimentation, and colloids
Uploaded: 2023-06-23T15:38:43.000Z
Duration: 1 min 17 s
Channel: JoVE

胶体和悬浮液是由两种或多种物理混合组分组成的非均相混合物。
在胶体中，溶质粒子的尺寸范围为1至1000纳米，小到无法单独观察。然而，这些溶质粒子可以散射光线，使胶体呈现半透明或不透明状态。它们能无限期地保持在溶液中，不会发生沉降。
细胞质溶胶是活细胞内部的半流体物质，由于其中分散着大量蛋白质和代谢物，因而属于胶体。
相比之下，悬浊液含有较大的颗粒，通常超过10000纳米，常可凭肉眼观察到。
当静置时，这些颗粒会沉降形成沉淀物。
血液是悬浊液的一个实例。当新鲜抽取的血液静置一段时间后，红细胞会沉降到容器底部。上层的液体部分称为血浆，其中含有小分子溶质的溶液，同时也是一种含有较大血浆蛋白的胶体。

胶体和悬浮液

玩耍的孩子通常会制作悬浮液，如混合泥浆和水、面粉和水，或者是在水中悬浮的固体颜料所制成的调色剂。这些悬浮液是由相对较大的肉眼可见的或通过放大镜可见的颗粒组成的异相混合物。它们是浑浊的，悬浮的颗粒在搅拌后会沉淀下来。悬浮液中的悬浮颗粒在一段时间的搅拌后会沉淀下来。悬浮液中颗粒的分离被称为沉淀。用于确定沉降速率的血液检测是通过测量试管中红细胞在一定的时间内从血液中的水分（称为血浆）沉淀下来的速度。在健康的身体中通常不会出现血细胞的快速沉降。然而，某些疾病的特定方面则可能会导致血细胞聚集在一起，这些沉积较重的血细胞会比正常的血细胞更快地沉淀到试管底部。

另一类混合物称为胶体（或胶体分散体），其表现的性质介于悬浮液和溶液之间。胶体中的颗粒比大多数简单分子要大，然而，当胶体颗粒的大小足够小时，它们便不会在静止时沉淀。胶体中的颗粒在足够大时能够散射光线，这种现象称为泰纳效应，这也是为什么胶体混合物看起来浑浊或不透明的原因，如聚光灯束。云层也是胶体混合物。它们是由比分子大得多但足够小而不会沉淀的水滴组成。一些胶体具有溶胶-凝胶转变的特性，可以在液态和固态（凝胶）之间可逆地进行转变。例如，明胶制品在冷藏时会凝固形成凝胶，再通过加热则可以变回液体。细胞溶胶中的溶胶-凝胶性质对于许多细胞的活动非常重要，如细胞分裂或细胞形态的变化。胶体溶液中的颗粒成分，以相对较小的量存在着，并被称为分散相。颗粒所分布的物质或溶液被称为分散介质。





这段文字改编自 <a href="https://openstax.org/books/anatomy-and-physiology-2e/pages/2-4-inorganic-compounds-essential-to-human-functioning">Openstax, Anatomy and Physiology 2e, Section 2.4: Inorganic Compounds Essential to Human Functioning</a> and <a href="https://openstax.org/books/chemistry-2e/pages/11-5-colloids">Openstax, Chemistry 2e, Section 11.5: Colloids</a>.

玩耍中的儿童常常会制作悬浊液，例如泥水混合物、面粉与水的混合物，或一种由固体颜料分散在水中制成的水彩颜料（蛋彩画颜料）。

Education

教育

JoVE Core

Anatomy and Physiology

解剖学与生理学

Unit 1

第 1 单元

Fundamentals of Chemistry

化学基础

KEY TERMS AND CONCEPTS

关键术语与概念

Colloids and Suspensions

suspensions, sedimentation, and colloids

Suspensions and colloids are two common kinds of mixtures seen in everyday life. Mud and water, flour and water, and tempera paint are suspensions. These mixtures are heterogeneous, which means their particles are not spread out evenly. The particles are relatively large and can be seen with the naked eye or a magnifying glass.

Suspension particles make mixtures cloudy, and they settle out after mixing. The settling of particles in a suspension is called sedimentation. A blood test can measure the rate of sedimentation by showing how fast red blood cells settle out of plasma, the watery part of blood, in a test tube over time. Rapid sedimentation is not usual in a healthy body, but some diseases can cause blood cells to clump together and sink faster than normal cells.

Colloids, also called colloidal dispersions, sit between suspensions and solutions. Their particles are larger than most simple molecules, but they are small enough that they do not settle out when left standing. Colloidal particles are still large enough to scatter light. This is known as the Tyndall effect, and it makes colloids look cloudy or opaque, like a beam from a searchlight.

Clouds are another example of a colloid. They contain water droplets that are bigger than molecules, but still small enough to stay suspended in the air. Some colloids can also change from a fluid sol to a solid gel and back again. Gelatin is one example. It forms a gel when chilled and can become liquid again when heated. The sol-gel behavior of cytosol, the fluid inside living cells, is important for cell division and for changes in cell shape.

In a colloid, the dispersed phase is the particulate part present in smaller amount. The dispersion medium is the substance that carries the particles throughout the mixture. These terms help describe how colloids are organized and why they behave differently from suspensions and solutions.

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Suspensions, Sedimentation, and Colloids

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