Final answer:
Most substances expand with increasing temperature and contract with decreasing temperature. This thermal expansion is due to the increase in kinetic energy of particles. Unique design features like expansion joints accommodate these changes to prevent damage.
Step-by-step explanation:
Most substances do not become warmer purely due to contraction or expansion; instead, they typically expand when their temperature increases and contract when it cools. The growth in the kinetic energy of atoms and molecules causes this, leading to more significant movements and thus larger intermolecular spaces. This principle of thermal expansion is utilized in devices like thermometers, where the expansion and contraction of a fluid, such as mercury or colored alcohol, indicate temperature changes. Liquids and solids can exert tremendous pressure when forced to expand in a constrained environment, possibly leading to damage or deformation of their containers. An exceptional case is water which expands upon freezing, unlike most other substances.
Materials that are isotropic expand uniformly in all dimensions, maintaining their shape but increasing in size. However, when materials like metal or concrete are exposed to temperature fluctuations, they need design features such as expansion joints to accommodate changes in size and prevent structural damage.
Some materials, however, exhibit negative thermal expansion in certain temperature ranges or dimensions. These materials actually contract when heated due to their unique atomic or molecular structures, which is an unusual behavior not commonly found in most substances.