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

Koloidy i zawiesiny są niejednorodnymi mieszaninami dwóch lub więcej fizycznie zmieszanych składników.
W koloidzie wielkość cząstek substancji rozpuszczonej waha się od 1 do 1000 nanometrów, na tyle małych, że są one niewidoczne pojedynczo. Jednak te cząsteczki substancji rozpuszczonej mogą rozpraszać światło, sprawiając, że koloidy wydają się półprzezroczyste lub nieprzezroczyste. Pozostają w roztworze na czas nieokreślony i nie osiadają.
Cytozol, półpłynny materiał wewnątrz żywych komórek, jest koloidem ze względu na liczne rozproszone w nim białka i metabolity.
Natomiast zawiesiny zawierają duże cząstki, zwykle powyżej 10000 nanometrów, często widoczne gołym okiem.
Pozostawione w spokoju cząstki te osiadają w postaci osadów.
Krew jest przykładem zawieszenia. Gdy świeżo pobrana krew pozostaje nienaruszona przez pewien czas, czerwone krwinki osiadają na dnie pojemnika. Górna płynna część, zwana osoczem krwi, jest roztworem małych substancji rozpuszczonych, a także koloidem zawierającym większe białka osocza.

koleoidy i zawiesiny

Podczas zabawy dzieci często tworzą zawiesiny, takie jak mieszanki błota i wody, mąki i wody, lub zawiesiny stałych barwników w wodzie, znane jako farby temperowe. Zawiesiny te to mieszaniny heterogeniczne składające się z relatywnie dużych cząstek widocznych gołym okiem lub przez szkło powiększające. Są mętne, a zawieszone cząstki osadzają się po wymieszaniu. Oddzielenie cząstek od zawiesiny nazywa się sedymentacją. Test krwi, mający na celu ustalenie tempa sedymentacji, mierzy, jak szybko czerwone krwinki w probówce opadają z wodnej części krwi (zwanej plazmą) w określonym czasie. Szybka sedymentacja krwinek zwykle nie występuje w zdrowym organizmie. Niemniej jednak, aspekty niektórych chorób mogą powodować sklejanie się krwinek, a te ciężkie skupiska krwinek opadają na dno probówki szybciej niż normalne krwinki.

Inna klasa mieszanin, zwana koloidami (lub dyspersjami koloidalnymi), wykazuje właściwości pośrednie między zawiesinami a roztworami. Cząstki w kolidzie są większe od większości prostych cząsteczek, jednak na tyle małe, że nie osadzają się po pozostawieniu na stojąco. Cząstki koloidalne są na tyle duże, że rozpraszają światło; zjawisko to nazywa się efektem Tyndalla; dlatego koloidalne mieszaniny wydają się mętne lub nieprzezroczyste, tak jak wiązki światła reflektorów. Chmury są również mieszaninami koloidalnymi. Składają się z kropelek wody znacznie większych od cząsteczek, ale na tyle małych, że nie opadają. Niektóre koloidy mają zdolność do przemiany sol-gel, która może przekształcać się odwracalnie z postaci płynnej do stałej (żelu). Na przykład, produkty żelatynowe stwardniają, tworząc żel, gdy są przechowywane w lodówce, a mogą się ponownie stać ciekłe w stanie podgrzanym. Właściwość sol-gel cytozolu, płynu komórkowego, jest niezbędna dla wielu procesów komórkowych, takich jak podział komórkowy czy zmiana kształtu komórki. Składnik cząstkowy roztworu koloidalnego, obecny w stosunkowo małej ilości, nazywa się fazą rozproszoną. Substancja lub roztwór, w którym jest rozproszona cząstka, nazywa się ośrodkiem dyspersyjnym.

Ten tekst jest adaptacją z <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>.

Koleoidy i zawiesiny

Bawiące się dzieci często tworzą zawiesiny, takie jak mieszaniny błota i wody, mąki i wody lub zawiesinę stałych pigmentów w wodzie znaną jako tempera ...

Education

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Kluczowe terminy i pojęcia

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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