Temperature, Kinetic Energy and particle mass

Temperature is a measure of the average ​​ (a)   of the particles in a system.

• kinetic energy
• speed
• velocity
• potential energy

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Which of the following has the fastest particles on average?

• Xenon gas at 75 ^oC.

  Each xenon particle has a mass of 131.29 amu.

• Oxygen gas at 75 ^oC.

  Each oxygen particle has a mass of 32.00 amu.

• Solid aluminum at 75 ^oC.

  Each aluminum particle has a mass of 27.00 amu.

• All the particles have the same average speed because the temperature is the same.

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Which of the following has particles with the highest average kinetic energy?

• Xenon gas at 75 ^oC.

  Each xenon particle has a mass of 131.29 amu.

• Oxygen gas at 75 ^oC.

  Each oxygen particle has a mass of 32.00 amu.

• Solid aluminum at 75 ^oC.

  Each aluminum particle has a mass of 27.00 amu.

• All the particles have the same average kinetic energy because the temperature is the same.

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When comparing a small sample of neon gas at 35 ^oC and a large sample of helium gas at 55 ^oC, which of the following is true? A particle of neon is heavier than a particle of helium. Choose all that apply.

• Both samples have the same average kinetic energy

• The average speed of the particles in both samples are the same.

• The helium particles have a higher average kinetic energy

• The neon particles have a higher average kinetic energy.

Answer explanation

Remember that temperature is a measure of the average kinetic energy of the particles in a system. Therefore substance with the higher temperature has particles with a higher average kinetic energy - the size of the sample doesn't matter, nor does the mass of the particles.

(side note) In this case the helium particles are definitely moving faster. Were the two samples at the same temperature (and therefore the same average KE), the helium particles would have a faster average speed - and since the helium is at a higher temperature, speeding them up even more, they would still be faster than the heavier neon particles.

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When comparing a small sample of helium gas at 35 ^oC and a large sample of helium gas at 35 ^oC, which of the following is true? Choose all that apply

• Both samples have the same average kinetic energy

• The average speed of the particles in both samples are the same.

• The smaller sample of helium gas has particles that are moving faster because the mass of the sample is smaller.

• The larger sample of helium gas has a higher kinetic energy because the mass of the sample is larger.

Answer explanation

Remember that temperature is a measure of the average kinetic energy of the particles in a system. Since both samples have the same temperature, they both have the same average kinetic energy - the size of the sample doesn't matter.

Since the particles of each are of the same substance AND at the same temperature, the particles are moving at the same average speed.

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If two substances have the same Temperature, their particles always have the same average Kinetic Energy.

• True

• False

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If two substances have the same Temperature, their particles always have the same average particle speed.

• True

• False

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If substance A has a higher temperature than substance B, the particles of substance A are always faster on average than the particles in substance B.

• True

• False

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If substance A has a higher temperature than substance B, the particles of substance A always have a higher average kinetic energy than the particles in substance B.

• True

• False

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Raising the temperature of an object always increases the average speed of the particles of that object.

• True

• False

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