Name: why some substances dissolve in water
Uploaded: 2025-05-22T09:05:33.000Z
Duration: 3 min
Channel: JoVE

K12 Standards

Minnesota Academic Standards in Science

9-12

Chemistry

3.2.1 9C.3.1.1.3

Solubility

المحلول عبارة عن خليط متجانس من مادتين رئيسيتين: المذاب والمذيب. المذيب موجود بكمية أكبر من المذاب.
في المحلول المخفف ، تكون نسبة المذاب بالنسبة للمذيب صغيرة ، بينما بالنسبة للمحلول المركز ، تكون النسبة كبيرة.
عند تكوين محلول ، لا يتفاعل المذاب والمذيب كيميائيا. بدلا من ذلك ، تعيد الجزيئات التوزيع ، مع جزيئات المذيبات الفردية المحيطة بجزيئات المذاب وتتفاعل من خلال قوى الجاذبية. تسمى عملية الذوبان هذه بالذوبان.
لصالح الذوبان ، يجب أن تكون تفاعلات المذاب والمذيب أقوى من تفاعلات المذيب والمذيب والمذاب.
في المحلول ، يمكن أن يكون المذاب والمذيب أي حالة من حالات المادة. الحل نفسه هو "مرحلة" واحدة.
عكس الذوبان هو هطول الأمطار ، الناجم عن تفاعلات قوية من المذاب والمذاب. عندما يساوي معدل الذوبان معدل هطول الأمطار ، يتم إنشاء توازن الذوبان.
قابلية ذوبان المذاب هي أقصى تركيز ممكن عند توازن الذوبان في كمية معينة من المذيب. تتأثر الذوبان بدرجة الحرارة والظروف الفيزيائية الأخرى مثل القطبية الجزيئية.
تذوب المواد المذابة غير القطبية في مذيبات غير قطبية من خلال قوى تشتت لندن بين الجزيئات ، بينما تذوب المواد المذابة القطبية أو الأيونية في المذيبات القطبية من خلال تفاعلات الأيونات ثنائية القطب أو ثنائي القطب ثنائي القطب.
الماء مذيب قطبي. المركبات المحبة للماء ، أو المحبة للماء ، قابلة للذوبان في الماء بسبب الشحنات الأيونية أو المجموعات القطبية التي تتيح تفاعلات قوية بما فيه الكفاية بين الماء والمذاب. إنها أقل قابلية للذوبان في المذيبات غير القطبية لأن التفاعلات المذابة المذابة أقوى بكثير من أي تفاعل محتمل بين المذيبات غير القطبية والجزيئات المذائبة القطبية.
المركبات غير القطبية غير القابلة للذوبان في الماء والقابلة للذوبان في الدهون مثل الزيوت كارهة للماء أو تخاف من الماء ، لأنها لا تستطيع تكوين روابط هيدروجينية للتنافس مع تفاعلات المذيبات والمذيبات.
تحتوي المركبات البرمائية أو البرمائية على مجموعات قطبية وغير قطبية. على سبيل المثال ، الصابون عبارة عن أملاح معدنية للأحماض الدهنية. في الماء ، تتجمع جزيئات الصابون في كرات تسمى المذيلات. تشير ذيول الأحماض الدهنية الكارهة للماء غير القطبية إلى الداخل بينما تكون رؤوسها القطبية المحبة للماء في الخارج.
عند إزالة بقع الزيت باستخدام الصابون ، تحيط ذيول الزيت غير القطبي لتشكيل مذيلات قابلة للذوبان في الماء ، مما يسمح بغسل الزيت.

الذوبان

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<h4>المحلول والذوبانية وتوازن الذوبانية</h4>
المحلول هو خليط متجانس يتكون من مذيب، وهو المكون الرئيسي، ومذاب، وهو المكون الثانوي. الحالة الفيزيائية للمحلول – صلبة أو سائلة أو غازية – هي عادة نفس حالة المذيب. غالبًا ما يتم وصف التركيزات المذابة بمصطلحات نوعية مثل المخفف (بتركيز منخفض نسبيًا) والمركز (بتركيز مرتفع نسبيًا).
في المحلول، تكون الجسيمات المذابة (الجزيئات و/أو الذرات و/أو الأيونات) محاطة بشكل وثيق بأنواع المذيبات وتتفاعل من خلال قوى التجاذب. عملية التحلل هذه تسمى الذوبان. عندما يكون الماء هو المذيب، تُعرف العملية بالترطيب. بالنسبة للإذابة، يجب أن تكون تفاعلات المذاب والمذيب أقوى من تفاعلات المذاب – المذاب والمذيب – المذيب. الترسيب هو عكس الذوبان ويحدث نتيجة للتفاعلات القوية بين المذاب والمذاب.
الذوبانية هي مقياس لأقصى كمية من المذاب يمكن إذابتها في كمية معينة من المذيب. تعد درجة الحرارة والضغط والقطبية الجزيئية من العوامل المهمة التي تؤثر على الذوبانية. يتم الوصول إلى توازن الذوبانية عندما يحدث ذوبان وترسيب جزيئات المذاب بمعدلات متساوية.

<h4>المثيل يذيب المثيل</h4>
للتنبؤ بما إذا كان المذاب قابلاً للذوبان في مذيب معين، فإن القاعدة العامة هي "المثيل يذيب المثيل". تذوب المذابات القطبية أو الأيونية في المذيبات القطبية بسبب تفاعلات الأيون – ثنائي القطب أو ثنائي القطب – ثنائي القطب مع جزيئات المذيب. لن يكون مثل هذا التفاعل ممكنًا مع مذيب غير قطبي. تذوب المواد المذابة غير القطبية في المذيبات غير القطبية من خلال قوى التشتت بين الجزيئات.

<h4>المركبات المحبة للماء، والكارهة للماء، والمحبّة للماء والدهون</h4>
الماء مذيب قطبي. تسمى المواد المذابة القابلة للذوبان في الماء "محبة للماء" أو "شره للماء". على سبيل المثال، عند إضافة كلوريد البوتاسيوم الصلب إلى الماء، تنجذب الأطراف الموجبة (الهيدروجين) لجزيئات الماء القطبية إلى أيونات الكلوريد السالبة، وتنجذب الأطراف السالبة (الأكسجين) للماء إلى أيونات البوتاسيوم الموجبة. تحيط جزيئات الماء بأيونات K- وCl+ الفردية، مما يقلل من القوى القوية التي تربط الأيونات معًا وتسمح لها بالانتقال إلى المحلول كأيونات مذابة.

يُطلق على المادة المذابة غير القابلة للذوبان في الماء اسم "كارهة للماء" أو " الخائفة من الماء". مثل هذه المواد المذابة، مثل الزيت، غير قادرة على تكوين روابط هيدروجينية مع جزيئات الماء المحيطة بها بسبب التفاعلات الأقوى بين المذاب – المذاب. ونتيجة لذلك، تتجمع جزيئات المذاب معًا وتبقى غير منحلة.

تسمى المركبات التي تحتوي على مجموعات قطبية وغير قطبية بـ " ثنائية الألفة" أو "المحبّة للماء والدهون". على سبيل المثال، الصابون، وهي أملاح الأحماض الدهنية. لديهم ذيل كاره للماء من الهيدروكربونات غير القطبية ورأس قطبي محب للماء. يمكن تفسير عملية التنظيف التي يقوم بها الصابون والمنظفات من خلال هياكل الجزيئات المعنية. يذوب الطرف الهيدروكربوني (غير القطبي) لجزيء الصابون أو المنظف في المواد غير القطبية أو ينجذب إليها، مثل الزيوت أو الشحوم أو جزيئات الأوساخ. ينجذب الطرف الأيوني للماء (القطبي). ونتيجة لذلك، تصبح جزيئات الصابون أو المنظفات موجهة نحو السطح البيني بين جزيئات الأوساخ والماء، بحيث تعمل كنوع من الجسر بين نوعين مختلفين من المادة، القطبية وغير القطبية. ونتيجة لذلك، تصبح جزيئات الأوساخ معلقة كجزيئات غروية ويتم غسلها بسهولة.

هذا النص مقتبس من <a href="https://openstax.org/books/chemistry-2e/pages/11-1-the-dissolution-process">OpenStax Chemistry 2e, Section 11.1: The Dissolution Process</a>, <a href="https://openstax.org/books/chemistry-2e/pages/11-3-solubility">Section 11.3: Solubility</a>, and <a href="https://openstax.org/books/chemistry-2e/pages/11-5-colloids">Section 11.5: Colloids</a>.
</div>

توازن الحل والذوبان والذوبان
المحلول عبارة عن خليط متجانس يتكون من مذيب ، المكون الرئيسي ، والمذاب ، ...

Education

JoVE Core

Organic Chemistry

الكيمياء العضوية

Unit 1

الوحدة الأولى

Covalent Bonding and Structure

الترابط التساهمي والبنية

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

why some substances dissolve in water

Solution formation depends on how solutes and solvents interact. A solution is a homogeneous mixture made of a solvent, which is the larger part, and a solute, which is the smaller part. The physical state of a solution is usually the same as the solvent. Concentration is often described as dilute for a low amount of solute or concentrated for a high amount of solute.

When a solute dissolves, its particles are surrounded by solvent species. This process is called solvation. If water is the solvent, it is called hydration. For solvation to happen, solute-solvent attractions must be stronger than the attractions within the solute and within the solvent. The opposite process is precipitation, which happens when solute particles are pulled together strongly enough to leave solution.

Solubility is the maximum amount of solute that can dissolve in a given amount of solvent. Temperature, pressure, and molecular polarity can all affect solubility. Solubility equilibrium occurs when dissolution and precipitation happen at the same rate. At that point, the amount dissolved stays constant.

A useful rule for predicting solubility is “like dissolves like.” Polar or ionic solutes usually dissolve in polar solvents because of ion-dipole or dipole-dipole attractions. These interactions do not work well with nonpolar solvents. Nonpolar solutes usually dissolve in nonpolar solvents through dispersion forces.

Water is a polar solvent, so substances that dissolve well in water are called hydrophilic, or water-loving. For example, when KCl is added to water, the hydrogen end of water is attracted to chloride ions, and the oxygen end is attracted to potassium ions. Water molecules surround the ions, weaken the forces holding them together, and allow them to move into solution as solvated ions. Substances that do not dissolve in water are called hydrophobic, or water-fearing. Oil is one example. It cannot form hydrogen bonds with water, so the particles cluster together and stay undissolved.

Some compounds contain both polar and nonpolar parts. These are called amphipathic, or amphiphilic. Soaps are an example because they are salts of fatty acids. They have a nonpolar hydrocarbon tail and a polar hydrophilic head. This structure helps soaps and detergents clean because the nonpolar end interacts with oil, grease, or dirt, while the ionic end interacts with water. The molecules line up at the boundary between the dirt and the water. They act like a bridge between polar and nonpolar matter, which helps suspend dirt as colloidal particles so it can be washed away.

Why Some Substances Dissolve in Water

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chemical bonds

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polar covalent bonds

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Arizona Science Standards

High School

Physical Science

HS+C.P1

HS+C.P1U1.4

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Temperature Dependence

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Reaction Rate

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9C.3.1.1.2

Solution Formation

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9C.3.2.1.2

3 Developing possible explanations of phenomena or designing solutions to engineering problems
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Why Some Substances Dissolve in Water

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