Which statement concerning heat and/or temperature is true?

Temperature is defined as a measure of the average kinetic energy of the molecules in a substance. When the temperature of a substance increases, it indicates that the molecules are moving faster, which in turn means that the kinetic energy is higher. This relationship between temperature and kinetic energy is fundamental in thermodynamics and helps explain various physical processes, such as phase changes (e.g., solid to liquid) and reactions that depend on thermal energy.

The other statements presented do not accurately describe the concept of temperature. For instance, referring to temperature as a measure of sound waves misrepresents its true definition since sound is a separate phenomenon reliant on pressure waves in a medium and not directly tied to temperature. Additionally, temperature does not remain constant during all chemical reactions; it can change depending on the reaction conditions and whether the reaction is exothermic or endothermic. Finally, temperature plays a critical role in physical state changes, such as melting and boiling, underscoring its importance in understanding the behavior of matter.