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

Коллоиды и суспензии представляют собой гетерогенные смеси двух или более физически смешанных компонентов.
В коллоиде размер частиц растворенного вещества колеблется от 1 до 1000 нанометров, что достаточно мало, чтобы они были невидимы по отдельности. Однако эти растворенные частицы могут рассеивать свет, в результате чего коллоиды кажутся полупрозрачными или непрозрачными. Они остаются в растворе на неопределенный срок и не оседают.
Цитозоль, полужидкий материал внутри живых клеток, является коллоидом из-за многочисленных белков и метаболитов, диспергированных в нем.
В отличие от них, суспензии содержат крупные частицы, обычно более 10000 нанометров, часто видимые невооруженным глазом.
Если их не потревожить, эти частицы оседают в виде осадка.
Кровь является примером суспензии. Когда свежевзятую кровь оставляют в покое в течение некоторого времени, эритроциты оседают на дне контейнера. Верхняя часть жидкости, называемая плазмой крови, представляет собой раствор небольших растворенных веществ, а также коллоид, содержащий более крупные белки плазмы.

Коллоиды и cуспензии

Дети, играя, часто создают суспензии, такие как смеси грязи и воды, муки и воды или суспензию твёрдых пигментов в воде, известную как акварель. Эти суспензии являются гетерогенными смесями, состоящими из относительно больших частиц, видных невооружённым глазом или видимых при помощи увеличительного стекла. Они мутные, и взвешенные частицы оседают после смешивания. Взвешенные частицы в суспензии оседают после некоторого времени смешивания. Разделение частиц от суспензии называется осаждением. Кровеносный анализ для определения скорости осаждения измеряет, насколько быстро эритроциты в пробирке оседают из водяной составляющей крови (известной как плазма) за установленное время. Быстрое осаждение клеток крови обычно не происходит в здоровом организме. Однако некоторые аспекты определённых заболеваний могут приводить к слипанию клеток крови, и эти тяжелые сгустки клеток крови оседают на дно пробирки быстрее, чем обычные клетки крови.

Другой класс смесей, называемых коллоидами (или коллоидными дисперсиями), проявляет свойства, промежуточные между свойствами суспензий и растворов. Частицы в коллоиде больше, чем у большинства простых молекул; однако коллоидные частицы достаточно малы, чтобы не оседать. Частицы в коллоиде достаточно большие, чтобы рассеивать свет; это явление называется эффектом Тиндаля; поэтому коллоидные смеси выглядят мутными или непрозрачными, например, лучи прожекторов. Облака также являются коллоидными смесями. Они состоят из капель воды, гораздо больших, чем молекулы, но достаточно маленьких, чтобы не оседать. Некоторые коллоиды обладают свойством превращаться из жидкости в твёрдое состояние (гель) и обратно. Например, желатиновые продукты застывают, образуя гель, когда они охлаждаются, а затем могут снова стать жидкими при нагревании. Это свойство цитозоля, жидкости живых клеток, играет важную роль во многих клеточных процессах, таких как деление или изменение формы. Частицы, составляющие коллоидное решение, находящиеся в относительно незначительном объёме, называются диспергированной фазой. Вещество или раствор, в котором распределены частицы, называется дисперсионной средой.

Адаптированная версия текста <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>.

Коллоиды и Cуспензии

Дети во время игры часто делают суспензии, такие как смеси грязи и воды, муки и воды, или суспензию твердых пигментов в воде, известную как темпера...

Education

JoVE Core

Anatomy and Physiology

Анатомия и физиология

Unit 1

Раздел 1

Fundamentals of Chemistry

Основы химии

KEY TERMS AND CONCEPTS

ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

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.

Suspensions, Sedimentation, and Colloids

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states of matter

Solids, Liquids, Gases, and Plasma

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colloids and suspensions

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key terms and concepts

Learn how suspensions settle, how sedimentation works, and why colloids stay cloudy without settling. Explore real examples like blood, clouds, and gelatin.

Suspensions, Sedimentation, and Colloids | JoVE K12

anatomy and physiology

JoVE Core Anatomy and Physiology showcases the anatomical and physiological details of the human body in comprehensive, clear, and engaging video animations. This collection of lessons focuses on the structures, components, functions, and requirements of the human body. It is complemented by scientist-in-action videos that demonstrate the application of this knowledge in real-world medical and research settings.

Suspensions, Sedimentation, and Colloids

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