Problem 30 - A Complete Resource Book in Chemistry for JEE Main

Question

People add sodium chloride to water while boiling eggs. This is to (a) decrease the boiling point of water (b) increase the boiling point of water (c) prevent breaking of eggs (d) make eggs tasty

Step-by-Step Solution

Answer

(b) increase the boiling point of water

Step 1: Understanding the Question

The question asks why people add sodium chloride (salt) to water when boiling eggs, providing four options to choose from. We need to identify which of these options correctly explains a behavior observed in cooking.

Step 2: Analyzing Each Option

We will examine each given option: (a) Decrease the boiling point of water: Adding salt actually increases the boiling point, so this option is incorrect. (b) Increase the boiling point of water: Salt raises the boiling point, requiring more heat for water to boil. This is plausible. (c) Prevent breaking of eggs: Salt may prevent cracks by increasing water density or because eggs cook more slowly. This is possible. (d) Make eggs tasty: Salt can enhance taste in foods, so this can also be true.

Step 3: Considering Practical Effects

While increasing the boiling point of water and improving taste are scientifically supported effects of adding salt, preventing egg breakage is a practical effect people believe. These can overlap as reasons for adding salt.

Step 4: Concluding the Most Suitable Option

The key scientific function of salt in boiling, in this context, is to increase the boiling point of water, which contributes to a better cooking process; options c and d are supplementary reasons. Thus, the answer focuses on the primary scientific effect.

Key Concepts

Colligative Properties

When we discuss colligative properties, we refer to those properties of solutions that depend on the number of particles dissolved in the solvent, rather than the type of particles. In simple terms, it's the count that matters, not what the particles are made of.
These properties include:

• Boiling point elevation
• Freezing point depression
• Osmotic pressure
• Vapor pressure lowering

When salt, which is chemically sodium chloride (NaCl), is added to water, it dissolves into sodium (Na⁺) and chloride (Cl⁻) ions. The presence of these ions increases the number of solute particles in the solution. This causes a phenomenon known as boiling point elevation.
Here’s the key to remember: More particles mean a higher boiling point. This means that the water will need a higher temperature to reach boiling after salt is added, explaining why it's relevant in the context of cooking. Understanding colligative properties sheds light on why adding substances like salt can change how solutions behave.

Sodium Chloride

Sodium chloride, commonly known as table salt, plays vital roles in our everyday lives. Chemically, it consists of equal numbers of sodium and chloride ions. When dissolved in water, it creates an ionic solution more complex than pure water.
Why do we use salt in cooking? There are several reasons:

• Flavor Enhancement: Salt naturally enhances the flavors of various foods.
• Boiling Point Elevation: As mentioned in colligative properties, salt increases the boiling point of water, which can result in faster cooking at higher temperatures.
• Texture Alteration: It can change the texture of certain dishes, making them more appealing.

Overall, sodium chloride is more than just a seasoning. It plays a functional role in cooking processes, from making food tastier to subtly altering how ingredients behave under heat. It’s a staple in kitchens worldwide for good reason.

Cooking Chemistry

Cooking isn't just an art; it's also a science involving chemistry! Each ingredient you add to your dish plays a specific chemical role. Let's dive into how this works, particularly with the common practice of adding salt to boiling water.
Adding salt to water is a perfect example of kitchen chemistry at its best. When you add salt, you aren't just seasoning your food. You're participating in a chemical process that changes the way water boils and cooks your dish.
Here's how it works:

• Temperature Control: The addition of salt increases the temperature at which water boils, allowing food to cook at a slightly higher temperature than it would in unsalted water.
• Crack Reduction: While scientifically debated, many cooks believe salt helps prevent eggs from cracking by increasing water density or stabilizing temperature.
• Flavor Development: Salt can encourage the development of complex flavors in dishes, acting as a catalyst for reactions like Maillard browning, which enhances flavors and creates a delicious aroma.

Cooking chemistry helps you understand the science behind traditional cooking techniques and why certain practices, like salting water, continue to be kitchen classics.