If the components of the substance can be separated by a chemical change only then it is a/ an

Explanation

To solve the question, "If the components of the substance can be separated by a chemical change only then it is a/an," we will analyze the options provided: Element, Compound, Mixture, and None of these.

### Step-by-Step Solution:

1. **Understanding the Terms**:
- **Element**: A pure substance made up of only one kind of atom. Elements cannot be broken down into simpler substances by chemical means.
- **Compound**: A substance formed when two or more elements are chemically combined in a fixed proportion. Compounds can only be separated into their components through chemical changes.
- **Mixture**: A combination of two or more substances that are not chemically bonded. Mixtures can be separated by physical means (like filtration or distillation).

2. **Analyzing the Question**:
- The question states that the components of the substance can only be separated by a chemical change. This indicates that we are looking for a substance that requires a chemical reaction to break it down into its individual components.

3. **Evaluating the Options**:
- **Element**: Cannot be separated into simpler substances by any means (chemical or physical). So, this option is incorrect.
- **Compound**: Requires a chemical change to separate into its constituent elements. This matches the condition given in the question.
- **Mixture**: Can be separated by physical means, which does not fit the requirement of the question. Thus, this option is incorrect.
- **None of these**: Since we have identified the correct answer, this option is also incorrect.

4. **Conclusion**:
- The only option that fits the criteria of being separable only by a chemical change is **Compound**.

### Final Answer:
The answer is **Compound**.