Problem 122 - A Complete Resource Book in Chemistry for JEE Main

Question

Which are the intensive properties? (a) Volume (b) Enthalpy (c) Temperature (d) Refractive index

Step-by-Step Solution

Answer

The intensive properties are (c) Temperature and (d) Refractive index.

Step 1: Understand Intensive vs Extensive Properties

Intensive properties are properties of matter that do not change with the amount of substance present. In contrast, extensive properties depend on the amount of matter. Examples of intensive properties include temperature and refractive index, while volume and enthalpy are extensive.

Step 2: Analyze Each Property

Let's review each given property: (a) Volume: It changes with the amount of substance, thus it is an extensive property. (b) Enthalpy: It depends on the mass of the substance, so it is also extensive. (c) Temperature: This property remains the same regardless of the amount of matter present, so it is intensive. (d) Refractive Index: It remains unchanged regardless of quantity, making it intensive.

Step 3: Identify Which Properties Are Intensive

Based on our analysis, the intensive properties from the given options are temperature and refractive index, as they do not depend on the quantity of matter.

Key Concepts

Intensive vs Extensive Properties

Understanding the difference between intensive and extensive properties is crucial for comprehending the characteristics of materials. Intensive properties are those characteristics that do not depend on the quantity of the substance. This means that no matter how much material you have, these properties remain constant. They help in identifying substances because they are unique to the type of material rather than its amount. On the other hand, extensive properties are affected by the size or extent of the system. These properties change when you alter the amount of substance. For example:

• Adding more substance increases volume, which makes volume an extensive property.
• Increasing the mass of a substance raises its enthalpy, which makes enthalpy extensive as well.

Recognizing the nature of these properties helps in studying and identifying materials effectively.

Examples of Intensive Properties

Intensive properties are often used to characterize and identify a substance because they remain unchanged even when the amount of the substance varies. Some common examples include:

• Temperature: No matter how large or small your sample is, the temperature remains the same for that material.
• Refractive Index: This is a measure of how light propagates through a medium, and it remains constant regardless of how much of the material there is.

These properties do not give information about the amount of matter present but can reveal much about the nature and identity of the substance.

Properties of Matter

Properties of matter are characteristics that define the behavior and qualities of substance. These can be categorized broadly into physical and chemical properties. Physical properties are observed without changing the composition of the substance. They include both intensive and extensive properties:

• Intensive properties: Discussed above, they are independent of the amount like density and melting point.
• Extensive properties: Depend on the amount such as mass and volume.

Chemical properties, on the other hand, involve the reactivity of a substance and how it changes into different substances. Understanding these properties, whether physical or chemical, intensive or extensive, helps in the detailed study and application of materials.