When a blacksmith strikes a piece of metal with a hammer, the repeated impacts cause energy to be transferred to the metal, leading to changes in its properties. On a microscopic level, the following changes occur:
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The average speed of the particles increased: As the metal is hammered, energy is added to it in the form of kinetic energy from the hammer strikes. This energy increases the average speed of the particles, causing them to vibrate more intensely. As a result, the temperature of the metal rises, which can lead to a glow as it becomes hot.
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The potential energy of the particles decreased: As the particles gain kinetic energy from the applied force, their structure may change, and they can rearrange into more favorable configurations that lower their potential energy.
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The kinetic energy of the particles decreased: This statement is incorrect in the context of hammering the metal. In fact, the kinetic energy of the particles increases due to the energy transferred from the hammering process.
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The individual temperature of the particles increased: While this is true, it is a less accurate descriptor of the microscopic behavior compared to the first statement. The "temperature" of an object is related to the average kinetic energy of its particles.
Overall, the most accurate description of the changes that lead to the visible changes in the properties of the metal is "The average speed of the particles increased." This increase corresponds directly to an increase in temperature and contributes to the metal becoming more malleable.