Question

Detergents are compounds that are dissolved in water. However, they are also able to dissolve hydrophobic stains, such as oil and grease in clothing and other fabrics. How are these compounds able to fulfill both hydrophilic and hydrophobic functions? A. They contain a hydrophobic core molecule encased in a hydrophilic shell. B. They can ionize into two parts; one part is ionic, and the other part is hydrophobic. C. They have two states; in water they are ionic, and in hydrophobic solvents they form nonpolar ring structures. D. They have two functionally distinct parts; one side is a hydrophobic chain, and the other end is polar and ionic.

Short answer

D

Step-by-step solution

Understanding the Problem

Identify that the problem is asking about how detergents can dissolve both water-soluble and hydrophobic substances.

Analyzing the Options

Review the given options (A, B, C, and D) and evaluate what each one suggests about the structure of detergent molecules.

Applying Knowledge of Detergent Structure

Recall that detergents have molecules with both hydrophilic (water-loving) and hydrophobic (oil-loving) parts. This structure allows them to interact with both water and oil.

Eliminating Incorrect Options

Option A suggests a hydrophobic core encased in a hydrophilic shell, which does not accurately describe detergent molecules. Option B suggests ionization into two parts, which is not consistent with typical detergent behavior. Option C implies that detergents change states between ionic and nonpolar ring structures, which is not correct.

Identifying the Correct Option

Option D correctly describes that detergents have two functionally distinct parts: a hydrophobic chain and a polar, ionic end. This allows them to interact with both hydrophilic and hydrophobic substances.

Key concepts

hydrophilic

A hydrophilic substance loves water. The word 'hydrophilic' itself means 'water-loving.' These molecules easily dissolve or interact well with water. In detergents, the hydrophilic part is typically a polar, ionic end. This end is designed to interact with water, ensuring that the detergent can mix and dissolve in it. This is crucial for the cleaning process because it enables the detergent to interact with water and wash away water-soluble dirt and residues. Some key features of hydrophilic substances include:

• High solubility in water
• Attraction to water molecules
• Ability to form hydrogen bonds with water

Understanding the hydrophilic property in detergents helps in realizing how they can be washed away with water, taking the grime along with them.

hydrophobic

Hydrophobic substances repel water. The term 'hydrophobic' means 'water-fearing.' These molecules do not dissolve in water. Instead, they tend to clump together to avoid water. In detergents, the hydrophobic part is usually a non-polar chain. This end is designed to interact with oils, grease, and other hydrophobic substances, making it easy to trap and lift these stains from fabrics. Essential traits of hydrophobic substances include:

• Poor solubility in water
• Tendency to merge with oils and fats
• Formation of micelles in the presence of detergents

Recognizing the hydrophobic component in detergents elucidates why they can effectively clean greasy and oily stains.

amphiphilic molecules

Detergents are amphiphilic molecules. The term 'amphiphilic' means that a molecule has both hydrophilic (water-loving) and hydrophobic (water-fearing) parts. This dual nature allows the molecule to interact with both water and oil. In practical terms, an amphiphilic detergent molecule has a hydrophilic head and a hydrophobic tail. This structure makes detergents incredibly versatile in breaking down and washing away different kinds of stains. Advantages of amphiphilic molecules include:

• Ability to form micelles
• Versatility in both aqueous and oily environments
• Efficiently trapping and removing diverse stains

Understanding amphiphilic properties helps in comprehending how detergents can simultaneously attract water and oil, aiding in effective cleaning.

surfactants

Surfactants are the active cleaning agents in detergents. The term 'surfactant' stands for 'surface-active agent.' These molecules reduce surface tension between different substances, such as water and oil. By lowering the surface tension, surfactants allow water and oil to mix more easily, thereby aiding in the removal of stains. Detergents are composed of surfactants that include both hydrophilic and hydrophobic parts. The primary functions of surfactants include:

• Reducing surface tension
• Promoting the mixing of oil and water
• Forming micelles to trap dirt and oil

Recognizing the role of surfactants illuminates the process of how detergents can clean effectively by making water and oil interact, leading to the emulsification and removal of stains.