What happens to a rod’s length when it is raised in temperature?

When a rod is raised in temperature, it experiences thermal expansion. This is a physical property of materials whereby they tend to expand in response to increases in temperature. As the temperature rises, the molecules within the material gain kinetic energy and move apart, which results in an increase in the length of the rod. This effect is generally uniform along most materials, meaning that the entire length of the rod expands uniformly rather than only in parts.

It's important to note that while some materials may expand unevenly under certain conditions or in complex geometries, the typical response to an increase in temperature for most rods is an overall increase in length. This is why the correct answer indicates that the length increases when the temperature is raised.