As a substance is heated, its ____ tends to increase.

When a substance is heated, its volume tends to increase due to the principles of thermal expansion. As the temperature of a material rises, the kinetic energy of its particles increases, causing them to move more vigorously and occupy more space. This phenomenon is observed in most substances, particularly in liquids and solids, where an increase in temperature generally leads to an increase in volume.

The concept of thermal expansion applies to gases as well, but in gases, the increase in volume can also result in changes in pressure if the gas is contained in a fixed volume. However, the primary focus here is on the general behavior of materials when they are heated, which consistently shows an increase in volume.

Resistance and conductance relate to electrical properties, where resistance usually increases with temperature in conductive materials while conductance decreases. These characteristics are not directly related to the concept of heating a substance in the context of its physical dimensions. Therefore, the correct assertion regarding the increase as a substance is heated is the increase in its volume.