Is there a substance that does not expand when heated and contract when cooled?

The assertion that all substances expand when heated and contract when cooled is grounded in the principles of thermal expansion, which describes how most materials behave when their temperature changes. When a substance is heated, the kinetic energy of its particles increases, resulting in greater movement and a tendency to occupy more space. This principle applies across various states of matter, including solids, liquids, and gases.

Although there are anomalies in behavior (for instance, water expands when it freezes), the general rule holds true for the majority of materials. This means that for metals, gases, and other common substances, heating them typically leads to expansion, while cooling leads to contraction.

Consequently, the assertion that certain substances do not follow this rule does not align with the fundamental understanding of thermal dynamics. Hence, the statement that all substances expand when heated and contract when cooled stands correct.