What factor makes it easier for a solid to absorb heat and ignite?

The surface-to-mass ratio significantly influences a solid's ability to absorb heat and kindle. A higher surface-to-mass ratio means that a larger area of the solid is exposed relative to its volume. This increased exposure facilitates more effective energy transfer, allowing heat to penetrate and raise the temperature of the solid material more quickly, ultimately making it easier for ignition to occur.

For example, consider a fine powder compared to a solid block of the same material. The powder has a much higher surface-to-mass ratio, enabling it to absorb heat rapidly and ignite faster. This characteristic is essential in fire behavior, as materials with a higher ratio ignite more readily under similar conditions than denser, more massive counterparts that have less surface area for heat absorption.

While size, shape, and temperature play roles in fire dynamics, it is the surface-to-mass ratio that directly affects the material's capacity to absorb heat efficiently and reach ignition temperature.