Skip to main content
Ch 18: A Macroscopic Description of Matter
Knight Calc - Physics for Scientists and Engineers 5th Edition
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Not the one you use?Change textbook
Chapter 18, Problem 28a

A gas with initial state variables p1, V1, and T1 expands isothermally until V2 = 2V1. What are T1?

Verified step by step guidance
1
Step 1: Recognize that the process is isothermal, meaning the temperature remains constant throughout the expansion. Therefore, T₁ = T₂.
Step 2: Recall the ideal gas law, which is expressed as PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the gas constant, and T is temperature.
Step 3: Since the temperature is constant (T₁ = T₂), the product of pressure and volume remains constant during the expansion. This is expressed as p₁V₁ = p₂V₂.
Step 4: Substitute the given relationship for the final volume, V₂ = 2V₁, into the equation p₁V₁ = p₂V₂ to find the relationship between p₁ and p₂.
Step 5: Conclude that since the temperature remains constant, T₂ = T₁. No further calculation is needed for T₂.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
2m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Isothermal Process

An isothermal process is a thermodynamic process in which the temperature of the system remains constant. For an ideal gas, this means that any heat added to the system is used to do work, rather than increasing the internal energy. In this scenario, since the gas expands isothermally, the temperature T₂ will equal the initial temperature T₁.
Recommended video:
Guided course
06:13
Entropy & Ideal Gas Processes

Ideal Gas Law

The Ideal Gas Law is a fundamental equation in thermodynamics that relates the pressure, volume, temperature, and number of moles of an ideal gas. It is expressed as PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the ideal gas constant, and T is temperature. This law helps in understanding how changes in volume and temperature affect the state of the gas during the isothermal expansion.
Recommended video:
Guided course
07:21
Ideal Gases and the Ideal Gas Law

Charles's Law

Charles's Law states that the volume of a gas is directly proportional to its temperature when pressure is held constant. This relationship implies that if the volume of a gas increases, its temperature must also increase, provided the pressure does not change. In the context of the isothermal expansion, while the volume doubles, the temperature remains constant, reinforcing the concept that T₂ = T₁.
Recommended video: