A solid block is warmed from 15 degrees Celsius to 45 degrees Celsius. In a solid, particles stay in place but vibrate. What happens to the particle vibrations when the temperature increases?
- They vibrate with smaller amplitude because higher temperature reduces motion in solids.
- They vibrate more vigorously (greater average kinetic energy). (correct answer)
- They stop vibrating because solids cannot gain kinetic energy.
- Their vibration depends only on the block's mass, not on temperature.
Explanation: This question tests understanding that temperature is a measure of the average kinetic energy of particles—how fast particles are moving on average. Temperature measures the average kinetic energy (energy of motion) of particles in a substance, not the total energy or the energy of just one particle but the average across all the particles—when temperature is high, particles move rapidly on average with high kinetic energy, and when temperature is low, particles move slowly on average with low kinetic energy, which is why a thermometer reading tells us about particle motion. When thermal energy is added to the solid block (heating from 15°C to 45°C), particles absorb this energy and their kinetic energy increases, making them vibrate more vigorously—in solids, particles stay in fixed positions but vibrate around those positions, and higher temperature means larger amplitude vibrations with greater average kinetic energy. Choice B is correct because it accurately states that particles vibrate more vigorously with greater average kinetic energy when temperature increases. Choice A reverses the relationship, claiming higher temperature reduces motion in solids, when actually temperature and particle motion are directly proportional: higher temperature always means more vigorous particle vibration in solids. To understand temperature and particle motion in solids: (1) temperature measures average particle kinetic energy, (2) in solids this energy appears as vibration amplitude, (3) heating increases vibration vigor, cooling decreases it. Real-world connection: this is why railroad tracks have gaps between sections—on hot days, the metal particles vibrate more vigorously and take up more space (thermal expansion), so without gaps the tracks would buckle; on cold days, particles vibrate less and the metal contracts.