Student Exploration: Temperature and Particle Motion
Vocabulary: absolute zero, Kelvin scale, kinetic energy, Maxwell-Boltzmann distribution, molar mass, molecule, temperature, universal gas constant
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
Why is hot air hot?
Why is cold air cold?
Air consists of tiny particles called molecules. How do you think the molecules move in hot and in cold air?
The Temperature and Particle Motion Gizmo™ illustrates how the molecules of gas move at different temperatures. In this Gizmo, temperature is measured on the Kelvin scale, which measures temperature from absolute zero, the coldest possible temperature (-273.15 °C). Each unit on the Kelvin scale is equivalent to 1 °C: 273.15 K = 0 °C, and 373.15 K = 100 °C.
Check that the selected gas is Hydrogen and the Temperature is 300 K.
Describe the motion of the hydrogen molecules:
Are all of the molecules moving at the same speed?
Get the Gizmo ready:
Check that the selected gas is Hydrogenand the Temperature is set to 300 K.
Question: How is the temperature of a gas related to the motion of gas molecules?
Observe: Move the Temperatureslider back and forth. Focus on the particle motion at left.
What do you notice?
Analyze: The temperature of a substance is a measure of the average kinetic energyof its particles (kinetic energy is the energy of motion). The kinetic energy (KE) of a particle is equal to its mass times the square of its velocity, divided by two:
Based on the formula for kinetic energy, how will the temperature change if you increase the average velocity of the molecules in a gas? ______________________
How will the temperature change if you increase the mass of the gas molecules?
Predict: Oxygen molecules are sixteen times as massive as hydrogen molecules. At the same temperature, which type of molecule would you expect to move faster? Explain.
Check: Test your prediction by choosing Oxygen from the Select a gas menu.
What do you see?
Explain: Based on the definition of temperature given above, explain why oxygen molecules move more slowly than hydrogen molecules at the same temperature.