Which Of The Following Is Not An Intensive Property

Volume is the key to understanding intensive versus extensive properties in thermodynamics and material science. The distinction lies in how these properties change when the amount of substance changes. While intensive properties, like temperature and density, remain constant regardless of the quantity of the substance, extensive properties, like volume, directly depend on the amount of matter being considered. Therefore, the answer to "which of the following is not an intensive property?" will always point to an extensive property such as volume, mass, or energy.

Let's delve into a comprehensive exploration of intensive and extensive properties, providing a clear understanding of their differences, significance, and practical applications.

Understanding Intensive Properties

Intensive properties are characteristics of a substance that do not depend on the amount of matter present. These properties are inherent to the substance itself and remain constant regardless of how much of the substance you have. Think of it this way: whether you have a drop of water or a swimming pool full of water, the boiling point of water will still be 100°C (at standard atmospheric pressure).

Here are some key aspects of intensive properties:

• Independence from Quantity: The defining characteristic. Intensive properties are independent of the system's size or extent.
• Bulk Properties: Often referred to as bulk properties because they describe the overall nature of the substance, not just individual particles.
• Examples: Common examples include temperature, pressure, density, color, hardness, melting point, boiling point, specific heat, and refractive index.

Common Examples of Intensive Properties Explained

To solidify the understanding, let's examine some common intensive properties in detail:

• Temperature: This is a measure of the average kinetic energy of the molecules within a substance. Whether you have a cup of coffee or a bathtub full of coffee, if both are at 60°C, the average kinetic energy of the molecules is the same in both.

• Pressure: Defined as force per unit area, pressure remains constant regardless of the amount of substance. For example, the atmospheric pressure at sea level is approximately 101.3 kPa, whether you are measuring it in a small room or across an entire beach.

• Density: This is defined as mass per unit volume. Crucially, while mass and volume are extensive properties, their ratio (density) is an intensive property. A gold bar and a gold nugget have the same density, even though they have drastically different masses and volumes. Density helps identify materials; pure gold always has a density of 19.3 g/cm³.

• Color: The color of a substance is an intensive property as it does not change with the amount of the substance. A small piece of copper will have the same reddish-brown color as a large copper sheet.

• Hardness: This is the resistance of a material to localized plastic deformation, such as indentation or scratching. The hardness of a diamond remains the same whether it's a small gem or a large, uncut stone.

• Melting Point & Boiling Point: These are the temperatures at which a substance changes state (solid to liquid and liquid to gas, respectively). These temperatures are constant for a given substance under specific conditions (like pressure), regardless of the quantity.

• Specific Heat: The amount of heat required to raise the temperature of one gram of a substance by one degree Celsius (or one Kelvin). This value is specific to the substance and does not depend on the amount of the substance.

• Refractive Index: A measure of how much light bends when passing from one medium to another. It's a characteristic property of the substance and remains constant regardless of the amount.

Significance of Intensive Properties

Intensive properties are incredibly important in science and engineering for several reasons:

• Material Identification: Intensive properties like density, melting point, and refractive index are used to identify substances. These properties provide a "fingerprint" for a material.
• System Characterization: They help characterize the state of a system. Knowing the temperature and pressure of a gas, for example, helps determine its behavior.
• Predicting Behavior: Intensive properties are used in equations of state to predict how a substance will behave under different conditions.
• Quality Control: In manufacturing, intensive properties are monitored to ensure the quality and consistency of products.

Unveiling Extensive Properties

Extensive properties, in contrast to intensive properties, depend on the amount of matter present in the system. The value of an extensive property is directly proportional to the size or extent of the system. If you double the amount of substance, you double the value of its extensive properties.

Key characteristics of extensive properties:

• Dependence on Quantity: The defining feature. The value of the property changes proportionally with the amount of substance.
• Additive: Extensive properties are additive. If you combine two systems, the total value of the extensive property is the sum of the values for each individual system.
• Examples: Common examples include mass, volume, energy (internal energy, enthalpy, entropy), and electrical charge.

Common Examples of Extensive Properties Explained

Let's explore some common extensive properties in more detail:

• Mass: This is a measure of the amount of matter in an object. If you have two identical objects, the combined mass is simply the sum of their individual masses.

• Volume: This is the amount of space a substance occupies. Doubling the amount of water in a container doubles the volume of water.

• Energy: This is the capacity to do work. Different forms of energy (kinetic, potential, internal) are all extensive. For example, the internal energy of a system increases with the amount of substance present.

• Enthalpy: A thermodynamic property of a system, defined as the sum of its internal energy and the product of its pressure and volume (H = U + PV). Because it depends on internal energy and volume, enthalpy is an extensive property.

• Entropy: A measure of the disorder or randomness of a system. The entropy of a system increases with the amount of substance and the number of possible arrangements of its molecules.

• Electrical Charge: The total electrical charge of an object depends on the number of charged particles it contains.

Significance of Extensive Properties

Extensive properties are essential for:

• Quantifying Systems: They allow us to quantify the size and composition of a system.
• Conservation Laws: Many fundamental laws of physics, such as the law of conservation of mass and the law of conservation of energy, are based on extensive properties.
• Scaling Systems: Extensive properties help us scale systems up or down. For example, knowing the mass of a reactant allows us to calculate the amount of product that will be formed in a chemical reaction.

Intensive vs. Extensive: A Direct Comparison

Ratios Can Change the Game

It is important to note that while individual properties can be classified as intensive or extensive, the ratio of two extensive properties can result in an intensive property. The most prominent example of this is density (ρ), which is defined as mass (m) divided by volume (V):

ρ = m/V

Both mass and volume are extensive properties. However, their ratio, density, is an intensive property. This is because if you double the mass, you also double the volume, and the ratio remains constant.

Examples and Applications

Let's consider some practical examples to illustrate the difference between intensive and extensive properties.

Example 1: Heating Water

• Scenario: You have a cup of water and a pot of water, both initially at room temperature (25°C). You heat both until they reach their boiling point (100°C).

• Analysis:

  • Temperature: The boiling point (100°C) is an intensive property. Both the cup of water and the pot of water will reach the same boiling point, regardless of the amount of water.
  • Heat Required: The amount of heat required to raise the temperature of the water to boiling point is an extensive property. The pot of water, having a larger mass, will require significantly more heat than the cup of water.
  • Mass and Volume: Both are extensive properties. The pot of water has a greater mass and volume than the cup of water.
  • Density: The density of the water is an intensive property. Both the cup and pot of water will have approximately the same density at a given temperature.

Example 2: Comparing Gold Samples

• Scenario: You have a small gold nugget and a large gold bar.

• Analysis:

  • Density: The density of gold is an intensive property. Both the nugget and the bar will have the same density (approximately 19.3 g/cm³). This is a key identifier of gold.
  • Mass and Volume: These are extensive properties. The gold bar has a significantly larger mass and volume than the gold nugget.
  • Melting Point: The melting point of gold is an intensive property. Both the nugget and the bar will melt at the same temperature (1064°C).
  • Internal Energy: The total internal energy of the gold is an extensive property. The gold bar has a greater internal energy due to its larger mass.

Example 3: Chemical Reactions

• Scenario: You are performing a chemical reaction in a lab.

• Analysis:

  • Temperature: The temperature at which the reaction is carried out is an intensive property.
  • Pressure: The pressure at which the reaction is carried out is an intensive property.
  • Volume of Reactants: The volume of reactants used is an extensive property.
  • Mass of Products: The mass of the products formed is an extensive property.
  • Concentration: The concentration of the reactants is an intensive property.

Importance Across Scientific Disciplines

The distinction between intensive and extensive properties is fundamental across various scientific disciplines:

• Thermodynamics: Essential for defining the state of a system and analyzing energy transfer.
• Chemistry: Used in stoichiometry, solution chemistry, and characterizing chemical reactions.
• Materials Science: Crucial for understanding material properties and behavior.
• Engineering: Important for designing and scaling processes and equipment.
• Physics: Relevant in various areas, including mechanics, electromagnetism, and statistical mechanics.

Common Misconceptions

• Confusing Density with Mass or Volume: Remember that density is the ratio of mass to volume and is therefore intensive, while mass and volume themselves are extensive.
• Assuming All Physical Properties Are Extensive: Many physical properties like temperature, color, and hardness are intensive.
• Neglecting the Importance of Ratios: The ratio of two extensive properties can be intensive and very useful for characterization.

Conclusion

Understanding the distinction between intensive and extensive properties is crucial for comprehending the behavior of matter and applying scientific principles effectively. Intensive properties are independent of the amount of substance, while extensive properties are directly proportional to the amount. The ability to identify and differentiate these properties is essential in various scientific and engineering disciplines, from thermodynamics to materials science. Knowing that volume is not an intensive property but an extensive one is a fundamental piece of this understanding. Recognizing the role of ratios, such as density, further refines this understanding, allowing for more accurate analysis and prediction of system behavior. With a firm grasp of these concepts, one can confidently approach scientific problems and make informed decisions based on the inherent characteristics of matter.