The enthalpy change for a reaction does not depend upon:

Options

A. the physical states of reactants and products
B. use of different reactants for the same product
C. the number of intermediate reaction steps
D. the differences in initial or final temperature of involved substances

Explanation

To determine what the enthalpy change for a reaction does not depend upon, we can analyze the options given and apply Hess's Law, which states that the total enthalpy change for a reaction is the sum of the enthalpy changes for the individual steps, regardless of the pathway taken.

### Step-by-Step Solution:

1. **Understanding Enthalpy Change**:
Enthalpy change (ΔH) is a measure of the heat content of a system. It can be affected by various factors during a chemical reaction.

2. **Applying Hess's Law**:
According to Hess's Law, the total enthalpy change for a reaction is independent of the route taken from reactants to products. This means that ΔH is not affected by the number of steps or intermediates involved in the reaction.

3. **Analyzing the Options**:
- **Option 1: Physical state of the reactants and products**: ΔH does depend on the physical state (solid, liquid, gas) because the enthalpy of formation varies with state.
- **Option 2: Use of different reactants for the same product**: ΔH will vary if different reactants are used, as different substances have different enthalpies.
- **Option 3: Number of intermediate reaction steps**: ΔH does not depend on the number of intermediate steps because of Hess's Law.
- **Option 4: Differences in the initial or final temperature of the involved substances**: ΔH does depend on the temperature, as it can affect the energy levels of the reactants and products.

4. **Conclusion**:
The enthalpy change for a reaction does not depend on the number of intermediate reaction steps. Therefore, the correct answer is **Option 3**.