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

קולואידים ומתלים הם תערובות הטרוגניות של שני רכיבים מעורבים פיזית או יותר.
בקולואיד, גודל החלקיקים המומסים נע בין 1 ל -1000 ננומטר, קטן מספיק כדי שהם יהיו בלתי נראים בנפרד. עם זאת, חלקיקים מומסים אלה יכולים לפזר אור, מה שהופך קולואידים להיראות שקופים או אטומים. הם נשארים בפתרון ללא הגבלת זמן ולא מתיישבים.
ציטוזול, החומר הנוזלי-למחצה בתוך תאים חיים, הוא קולואיד בגלל החלבונים והמטבוליטים הרבים המפוזרים בו.
לעומת זאת, מתלים מכילים חלקיקים גדולים, בדרך כלל מעל 10000 ננומטר, לעתים קרובות גלויים לעין בלתי.
כאשר הם נותרים ללא הפרעה, חלקיקים אלה שוקעים כמשקעים.
דם הוא דוגמה להשעיה. כאשר דם טרי נמשך נשאר ללא הפרעה במשך זמן מה, תאי הדם האדומים להתיישב בתחתית המיכל. החלק הנוזלי העליון, הנקרא פלסמה בדם, הוא תמיסה של מומסים קטנים וכן קולואיד המכיל חלבוני פלזמה גדולים יותר.

קולואידים ותרחיפים

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ילדים שמשחקים עושים לעתים קרובות תרחיפים כמו תערובות של בוץ ומים, קמח ומים, או תרחיף של פיגמנטים מוצקים במים המכונה צבע טמפרה. תרחיפים אלו הם תערובות הטרוגניות המורכבות מחלקיקים גדולים יחסית הנראים לעין בלתי מזוינת או נראים בזכוכית מגדלת. הם עכורים, והחלקיקים המרחפים מתיישבים לאחר הערבוב. החלקיקים המרחפים בתרחיף מתייצבים לאחר זמן מה של ערבוב. הפרדת חלקיקים מתרחיף נקראת שקיעה. בדיקת דם לקביעת קצב השקיעה מודדת באיזו מהירות כדוריות דם אדומות במבחנה מתייצבות מהחלק המימי של הדם (המכונה פלזמה) במשך זמן מוגדר. שקיעה מהירה של תאי דם אינה מתרחשת בדרך כלל בגוף בריא. ובכל זאת, היבטים של מחלות מסוימות עלולים לגרום לתאי דם להתקבץ יחד, וגושים כבדים אלה של תאי דם מתיישבים בתחתית המבחנה מהר יותר מאשר תאי דם רגילים.

מחלקה נוספת של תערובות הנקראות קולואידים (או פיזור קולואידיאלי) מציגות תכונות ביניים בין אלו של תרחיפים ותמיסות. החלקיקים בקולואיד גדולים יותר מרוב המולקולות הפשוטות; עם זאת, חלקיקים קולואידים קטנים מספיק כדי שהם לא מתיישבים עם עמידה. החלקיקים בקולואיד גדולים מספיק כדי לפזר אור; תופעה הנקראת אפקט טינדל וזו הסיבה שתערובות קולואידיות נראות עכורות או אטומות, כמו קרני זרקור. עננים הם גם תערובות קולואידיות. הם מורכבים מטיפות מים גדולות בהרבה ממולקולות אך קטנות מספיק כדי לא להתמקם. לחלק מהקולואידים יש את התכונה לעבור טרנספורמציות סול-ג'ל, שיכולות להפוך בצורה הפיכה ממצב נוזלי למצב מוצק (ג'ל). לדוגמה, מוצרי ג'לטין מתמצקים ויוצרים ג'ל בקירור, אשר יכול להיות נוזלי שוב בחימום. תכונת הסול-ג'ל של ציטוזול, הנוזל של תאים חיים, חיונית לפעילויות תאיות רבות, כגון חלוקת תאים או שינוי בצורת התא. המרכיב החלקיקי של תמיסה קולואידית, הקיים בכמות מינורית יחסית, נקרא הפאזה המפוזרת. החומר או התמיסה שלאורכו מופצים החלקיקים נקראים מדיום פיזור.

טקסט זה מותאם מ- <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>.
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ילדים במשחק לעתים קרובות לעשות תרחיפים כגון תערובות של בוץ ומים, קמח ומים, או תרחיף של פיגמנטים מוצקים במים המכונה טמפרה ...

Education

JoVE Core

Anatomy and Physiology

אנטומיה ופיזיולוגיה

Unit 1

יחידה 1

Fundamentals of Chemistry

יסודות הכימיה

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

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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the periodic table and organismal elements

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Chemical Symbols and Element Names

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Atomic Identity, Mass, and Isotopes

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atomic weight

Atomic Mass and Mole Calculations

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isotopes and radioisotopes

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electron behavior

Electron Shells and Discovery

Electrons are negatively charged subatomic particles that stay near the positively charged nucleus of an atom. They occupy spaces linked to energy levels called shells. They are also arranged into subshells and orbitals within each shell. An electron’s shell shows its general energy level. Electrons closer to the nucleus have less energy, while electrons farther away have more energy. The outer shells have more space, so they can hold more electrons than the inner shells. Subshells describe...

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How Atoms Bond to Reach Stability

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Ionic Bonds and Charge Transfer

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Polar and Nonpolar Covalent Bonds

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hydrogen bonds

Hydrogen Bonding and DNA Stability

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Atomic Charges, Bonds, and Compounds

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Solids, Liquids, Gases, and Plasma

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colloids and suspensions

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...

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Chemical Reaction Basics and Equilibrium

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Anabolism, Catabolism, and ATP Use

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Electron Transfer and Chemical Equilibrium

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Chemical Energy and Reaction Types

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Chemical Reaction Rates and Catalysts

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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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