When a glass rod is placed in steam, its length increases due to the thermal expansion of the material. However, the effect of thermal expansion on the width or diameter of the glass rod depends on the specific properties of the glass.
In general, the width or diameter of a solid object may also experience thermal expansion, although it might be less noticeable compared to the length changes. The expansion in width is typically related to the coefficient of linear expansion and the coefficient of volumetric expansion of the material.
Different materials have different coefficients of thermal expansion, which quantify how much a material expands or contracts in response to temperature changes. For most common types of glass, the coefficient of linear expansion is relatively small, meaning that the change in width due to thermal expansion is usually less significant compared to the change in length.
However, it's worth noting that the specific behavior of glass can vary depending on its composition and the manufacturing process. Some specialized glasses, such as borosilicate glass (e.g., Pyrex), have a lower coefficient of thermal expansion and exhibit less expansion in both length and width compared to ordinary glass.
In summary, while the length of a glass rod generally increases when exposed to steam due to thermal expansion, the change in width will also occur but might be relatively smaller and less noticeable, especially in common types of glass.