Which Of These Is An Extensive Property

Which of These is an Extensive Property? Understanding Extensive vs. Intensive Properties

Determining whether a property is extensive or intensive is fundamental to understanding the behavior of matter and systems in chemistry and physics. This article will delve deep into the differences between extensive and intensive properties, providing clear definitions, examples, and explanations to help you confidently identify which property falls into which category. We will explore various scenarios, using practical examples to solidify your understanding.

Extensive Properties: Defined

An extensive property is a physical property of a system that depends on the size or amount of matter in the system. This means that the value of the extensive property changes proportionally with the size of the system. If you double the amount of matter, you double the value of the extensive property. Think of it as a property that is additive.

Key Characteristics of Extensive Properties:

• Dependent on System Size: The defining feature is its direct relationship to the amount of matter present.
• Additive: The value for the combined system is simply the sum of the values for the individual parts.
• Examples: Mass, volume, length, weight, energy, enthalpy, entropy, heat capacity, and the number of moles are all classic examples.

Intensive Properties: Defined

In contrast, an intensive property is a physical property of a system that is independent of the amount of matter present. The value of an intensive property remains the same regardless of the size of the system. Whether you have a small sample or a large quantity, the intensive property will remain constant.

Key Characteristics of Intensive Properties:

• Independent of System Size: The core characteristic is its lack of dependence on the quantity of matter.
• Non-Additive: Combining systems doesn't simply add the intensive properties together; the resulting system will have the same intensive property as the individual components.
• Examples: Temperature, pressure, density, boiling point, melting point, refractive index, concentration, and specific heat are common examples.

Differentiating Extensive and Intensive Properties: A Detailed Comparison

The following table provides a side-by-side comparison of extensive and intensive properties to highlight their key differences:

Examples Illustrating the Difference

Let's examine some practical examples to solidify our understanding:

Scenario 1: Water

• Extensive: Consider two beakers. One contains 100ml of water, and the other contains 200ml. The volume of water is an extensive property. The total volume of water in both beakers is 300ml (100ml + 200ml). The mass of the water also follows this additive property.
• Intensive: The temperature of the water in both beakers is an intensive property. If both beakers are at 25°C, the combined system will also be at 25°C, not 50°C. Similarly, the density of water (approximately 1 g/ml at room temperature) remains the same regardless of the volume.

Scenario 2: A Collection of Identical Metal Blocks

• Extensive: The total mass of a collection of five identical metal blocks is five times the mass of a single block. The total volume follows the same principle.
• Intensive: The density of each block, and therefore the collection, remains the same. The melting point of the metal is another example of an intensive property; it will not change depending on the number of blocks.

Scenario 3: Mixing Solutions

• Extensive: When mixing two solutions, the total volume is the sum of the individual volumes (although this isn't always strictly true due to intermolecular interactions that can cause slight volume changes). The total number of moles of solute is also extensive.
• Intensive: The concentration of the resulting solution is not simply the sum of the individual concentrations. It depends on the total moles of solute and the total volume of the solution. The pH of the resulting solution depends on the relative amounts of acid and base but remains an intensive property.

Specific Heat Capacity: A Detailed Look at an Extensive Property

Specific heat capacity is an important concept often misinterpreted. While heat capacity is an extensive property, specific heat capacity is intensive.

• Heat capacity: This is the amount of heat required to raise the temperature of a substance by one degree Celsius (or one Kelvin). It's extensive because it depends on the mass of the substance. A larger mass requires more heat to change its temperature.

• Specific heat capacity: This is the amount of heat required to raise the temperature of one gram (or one mole) of a substance by one degree Celsius. It's intensive because it's normalized to a specific mass or amount of substance. The specific heat capacity of water is always approximately 4.18 J/g°C, regardless of the amount of water.

Practical Applications and Importance

Understanding the distinction between extensive and intensive properties is crucial in various fields:

• Chemistry: In stoichiometry, extensive properties like mass and moles are used for calculating quantities in chemical reactions. Intensive properties like density and concentration are crucial for determining the composition of solutions.

• Physics: In thermodynamics, extensive properties like internal energy and entropy are important for understanding the state of a system. Intensive properties such as temperature and pressure are used to define thermodynamic equilibrium.

• Engineering: In material science, intensive properties like strength, hardness, and conductivity are essential for material selection and design. Extensive properties, like the overall mass and volume of a structure, influence its structural integrity and stability.

Conclusion: Mastering the Difference

The ability to correctly classify properties as extensive or intensive is paramount for effective problem-solving in various scientific disciplines and engineering applications. By understanding the fundamental differences—dependence on the amount of matter and additivity—you can confidently analyze systems and make accurate predictions about their behavior. Remember that many properties can be transformed from extensive to intensive by normalizing them to a specific quantity (like specific heat capacity). This article has provided a comprehensive exploration of the topic, offering a clear framework for understanding and applying this crucial distinction in your work. Practicing with various examples will further solidify your grasp of this vital concept in physical science.