Of the following types of glass, the one with the smallest coefficient of thermal expansion is :

Options

A. safety glass
B. pyrex glass
C. soft glass
D. soda lime glass

Explanation

To determine which type of glass has the smallest coefficient of thermal expansion among the given options (safety glass, Pyrex glass, soft glass, or soda lime glass), we can follow these steps:

### Step-by-Step Solution:

1. **Understand Coefficient of Thermal Expansion**:
- The coefficient of thermal expansion quantifies how much a material expands when heated. A lower coefficient indicates that the material expands less with temperature changes.

2. **Identify the Types of Glass**:
- The options provided are:
- Safety glass
- Pyrex glass
- Soft glass
- Soda lime glass

3. **Research Each Type of Glass**:
- **Safety Glass**: Typically made by laminating or tempering regular glass, it has a moderate thermal expansion.
- **Pyrex Glass**: A borosilicate glass known for its low thermal expansion and high resistance to thermal shock. It is designed for laboratory and kitchen use.
- **Soft Glass**: Common glass with a higher thermal expansion coefficient, often used in decorative items.
- **Soda Lime Glass**: The most common type of glass, which has a relatively high coefficient of thermal expansion.

4. **Compare the Coefficients**:
- Pyrex glass is specifically engineered to have a low coefficient of thermal expansion, making it ideal for applications where thermal stability is crucial.
- The other types of glass (safety glass, soft glass, and soda lime glass) generally have higher coefficients of thermal expansion compared to Pyrex.

5. **Conclusion**:
- Based on the properties and applications of each type of glass, **Pyrex glass** has the smallest coefficient of thermal expansion among the options provided.

### Final Answer:
The type of glass with the smallest coefficient of thermal expansion is **Pyrex glass** (Option B).