The diagram shows four states of a system, each with different internal energy, E. (c) Write an expression for the difference in energy between State C and State D.

Verified step by step guidance

1. Identify the internal energies of State C and State D, denoted as E_C and E_D respectively.
2. Understand that the difference in energy between two states is calculated by subtracting the internal energy of one state from the other.
3. Write the expression for the difference in energy between State C and State D as \( \Delta E = E_C - E_D \).
4. Ensure that the signs are correct: if E_C is greater than E_D, \( \Delta E \) will be positive, indicating energy is released when moving from C to D.
5. If E_C is less than E_D, \( \Delta E \) will be negative, indicating energy is absorbed when moving from C to D.

Key Concepts

Internal Energy

Internal energy is the total energy contained within a system, encompassing both kinetic and potential energy of the particles. It is a state function, meaning it depends only on the current state of the system, not on how it reached that state. Understanding internal energy is crucial for analyzing thermodynamic processes and energy changes in a system.

State Function

A state function is a property of a system that depends only on its current state, not on the path taken to reach that state. Examples include internal energy, enthalpy, and pressure. In the context of the question, the difference in internal energy between two states (C and D) can be calculated directly from their respective energy values, illustrating the concept of state functions.

Energy Difference Calculation

Calculating the energy difference between two states involves subtracting the internal energy of one state from that of another. In this case, the expression for the difference in energy between State C and State D can be represented as ΔE = E_C - E_D. This calculation is fundamental in thermodynamics, allowing for the analysis of energy transfers and transformations within a system.