Question

a blacksmith strikes a piece of metal with a hammer repeatedly. the metal slowly begins to glow as the temperature increases, and the metal becomes more malleable. which changes on a microscopic level led to the visible changes in the properties of the metal? (1 point)
the kinetic energy of the particles decreased.
the potential energy of the particles decreased.
the individual temperature of the particles increased.
the average speed of the particles increased.

Explanation:

When the blacksmith strikes the metal, work is done on it. According to the kinetic - molecular theory, temperature is a measure of the average kinetic energy of the particles. As the temperature of the metal increases (it glows), the average kinetic energy of the particles increases. Since kinetic energy \(K = \frac{1}{2}mv^{2}\) (where \(m\) is the mass of the particle and \(v\) is the speed), an increase in kinetic energy (assuming the mass of the particles remains constant) means an increase in the average speed of the particles.

• The first option is wrong because if the kinetic energy of the particles decreased, the temperature would decrease.
• The second option: Potential energy is related to the position of particles (e.g., in a gravitational or electric field, or in terms of inter - particle forces like in a spring - like model for solids). Striking the metal mainly affects kinetic energy, not potential energy in the context of the given macroscopic changes (glowing and malleability due to temperature).
• The third option: Temperature is a measure of the average kinetic energy of a group of particles, not the "individual temperature" of particles (temperature is a macroscopic property related to the collective motion of particles).

Answer:

The average speed of the particles increased.