Which of the following is not a chemical change?

Options

A. rusting of iron
B. converting water into steam
C. making curd from milk
D. heating coal

Explanation

To determine which of the following options is not a chemical change, we need to understand the definition of a chemical change. A chemical change involves a chemical reaction where the original substances (reactants) transform into new substances (products) with different properties.

### Step-by-Step Solution:

1. **Identify the Options**: First, we need to look at the options provided in the question. While they are not listed here, we will analyze common examples that are often considered.

2. **Understand Chemical Changes**: A chemical change occurs when:
- New substances are formed.
- The properties of the original substances differ from the new substances.
- Examples include rusting of iron, burning of wood, and fermentation of sugar.

3. **Identify Physical Changes**: A physical change occurs when:
- The form or appearance of a substance changes, but its chemical composition remains the same.
- Examples include melting ice, boiling water, and dissolving sugar in water.

4. **Analyze Each Option**:
- **Rusting of Iron**: This is a chemical change as it produces iron oxide, which has different properties from iron.
- **Making Curd from Milk**: This is a chemical change because curd has different properties from milk.
- **Heating Coal**: This is a chemical change as it produces gases like CO2 and CO, which are different from coal.
- **Converting Water into Steam**: This is a physical change, as water changes from liquid to gas but remains H2O.

5. **Conclusion**: Based on the analysis, the option that is not a chemical change is **Converting Water into Steam**.

### Final Answer:
The process that is not a chemical change is **Converting Water into Steam**.