Question

You are looking at two bars made of solid aluminum. The first one has a temperature of 20 °C, while the second one has a temperature of 80 °C. Aluminum has a melting point of 1221 °C. Which of the following statements are correct? I. The particles in the 80 °C bar are moving around more freely in the sample.II. The particles in both bars are vibrating in place.III. The particles in the 80 °C bar have a higher average kinetic energy.I onlyII and IIIII onlyI, II, and III

Answer 1

According to the Kinetic Molecular Theory, the temperature of a sample is the average kinetic energy of particles in a substance.

This also expains the relationship between the temperature and the states of matter. Molecules in a solid are held close to each other, being able to vibrate but staying in place. If the molecules are able to move more freely, the sample is a liquid or a gas.

Since both bars have a temperature below their melting point, they are both solid. One bar has a greater temperature: 80ºC, while the other bar has a temperature of 20ºC. Since the temperature is related to the average kinetic energy of the sample, then the molecules in the 80ºC have a greater average kinetic energy.

Then, the statement I is incorrect because both bars are solid, so their molecules move around equally freely. The statements II and III are correct.

Therefore, the correct choice is: II and III.