Final answer:
Temperature measures how hot or cold an object is and is indicated by a thermometer's reading. It reflects the average kinetic energy of particles within a substance, affecting chemical reactions and state changes.
Step-by-step explanation:
Temperature is a fundamental concept in physics that measures how hot or cold an object is. It is operationally defined by the reading we get from a thermometer, a device designed to measure the temperature. Unlike the subjective sensations of hot and cold, which can vary based on different circumstances, the temperature given by a thermometer is a consistent and reliable measure. Temperature should not be confused with heat, which is the transfer of thermal energy due to a temperature difference.
Temperature is also related to the kinetic energy of particles: it represents the average kinetic energy of particles in a substance. In a hot substance, the particles move faster, and thus, the temperature is higher. When we talk about chemical reactions or state changes such as melting or boiling, an increase in temperature usually speeds up these processes and can cause substances to change from solid to liquid or liquid to gas.