Question

If the function \(p=p(T, v)\) is an equation of state, is \((\partial p / \partial T)_{v}\) a property? What are the independent variables of \((\partial p / \partial T)_{v} ?\)

Short answer

Yes, it is a property. The independent variables are T and v.

Step-by-step solution

- Understand the Partial Derivative

Identify that \(\frac{\partial p}{\partial T}\) means the rate of change of pressure \(p\) with respect to temperature \(T\) while keeping specific volume \(v\) constant.

- Analyze the Function

Determine that \(p = p(T, v)\) indicates pressure \(p\) is a function of temperature \(T\) and specific volume \(v\).

- Determine if it is a Property

Identify that a property is a characteristic or parameter that helps describe the state of a system. Since \(\frac{\partial p}{\partial T}\) at constant \(v\) describes how pressure changes with temperature at a constant volume, it is considered a property.

- Identify the Independent Variables

State that the independent variables for \(\frac{\partial p}{\partial T}\) at constant \(v\) are temperature (T) and specific volume (v).

Key concepts

Partial Derivatives

Partial derivatives play a vital role in understanding thermodynamic properties. The partial derivative \(\frac{\text{∂} p}{\text{∂} T}\text{ at constant } v \) gives us insight into how pressure \(p\) changes with temperature \(T\), while keeping the specific volume \(v\) constant. This type of derivative is essential because it helps us see how one variable influences another in isolation. For example, in the equation \(p = p(T, v)\), \(\frac{\text{∂} p}{\text{∂} T}|_{v}\) tells us the rate of change of pressure concerning temperature when the specific volume does not change. Understanding partial derivatives allows us to delve deeper into the characteristics and behaviors of various thermodynamic systems.

Equation of State

An equation of state is a mathematical model that expresses the relationship between different thermodynamic properties of a system. For instance, in the equation \(p(T, v)\), the pressure \(p\) is expressed as a function of temperature \(T\) and specific volume \(v\). Equations of state help us understand how these properties are interconnected. These equations often relate variables like pressure, temperature, and volume, helping predict the behavior of a system under different conditions. Familiar examples include the ideal gas law: \[ pV = nRT \] where \(p\) is pressure, \(V\) is volume, \(n\) is the number of moles, \(R\) is the gas constant, and \(T\) is the temperature. Using state equations, we can understand, predict, and manipulate the properties of gases and other substances.

Independent Variables

Independent variables are the inputs or predictors that we manipulate to see how they affect other variables in a system. In the context of thermodynamics, these are the variables we control or set while observing changes in other properties. For the partial derivative \(\frac{\text{∂} p}{\text{∂} T}|_{v}\) in our example, the independent variables are temperature \(T\) and specific volume \(v\). This means we are examining how pressure \(p\) changes as we vary the temperature, while keeping \(v\) constant. Understanding and identifying independent variables is crucial because they determine the scope and limits of our analysis. In experiments and calculations, correctly noting the independent variables ensures accurate and meaningful results.