Temperature and Particle Motion Gizmo

Temperature and Particle Motion Gizmo

Open Ended

What do you think is the difference between the motion of particles in hot air vs. cold air?

Open the Temperature and Particle Motion Gizmo

Lag in to Launchpad and click on the ExploreLearning icon.

Gizmo Warm-up

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.

Open Ended

Describe the motion of the hydrogen molecules

Multiple Choice

Are all of the molecules moving at the same speed?

• Yes

• No

• Cannot say

Multiple Choice

Check that the selected gas is Hydrogen and the Temperature is set to 300 K. Are both of these setting selected?

• Yes

• No

Open Ended

Move the Temperature slider back and forth. Focus on the particle motion at left. What do you notice? 

Multiple Choice

 The temperature of a substance is a measure of the average kinetic energy of 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: 

KE = mv² / 2

Based on the formula for kinetic energy, how will the temperature change if you increase the average velocity of the molecules in a gas? 

• It will increase exponentially

• It will increase in direct proportion to velocity

• It will decrease exponentially

• It will decrease in direct proportion to velocity

Open Ended

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.

Multiple Choice

Check: Test your prediction by choosing Oxygen from the Select a gas menu. What do you see?

• Oxygen moves faster at the same temp

• Oxygen moves slower at the same temp

• They move at the same speed

Open Ended

Explain: Based on the definition of temperature given earlier, (KE = mv² / 2) explain why oxygen molecules move more slowly than hydrogen molecules at the same temperature.

Activity B: Average Particle Velocity

Get the Gizmo ready: 

• Select Hydrogen gas.

Set the Temperature to 300 K.

Open Ended

Introduction: The graph on the right side of the Gizmo represents the Maxwell-Boltzmann distribution of particle velocities. The curve represents the probability of a particle moving at the velocity shown on the x-axis of the graph. The higher the curve, the greater the probability of finding a particle moving at that velocity will be.

Question: How are particle velocities distributed?

Observe: Move the Temperature slider back and forth. This time focus on the graph at right. What do you notice about the shape of the graph?

Multiple Choice

Analyze: Look at the left side of the graph as you raise the temperature from 50 to 1,000 K.

Even at the highest temperatures, are there still a few slow particles?

• Yes

• No

• Can't tell

Open Ended

Analyze: Look at the left side of the graph as you raise the temperature from 50 to 1,000 K. 

At what temperature do you see the widest variety of particle velocities?

Multiple Choice

Analyze: Look at the left side of the graph as you raise the temperature from 50 to 1,000 K.

In general, is the Maxwell-Boltzmann curve a symmetrical or an asymmetrical curve?

• Symmetrical

• Asymmetrical

• Can't tell

Open Ended

Estimate: Because particles have a range of velocities at any given temperature, it is useful to calculate the average velocity. Physicists express the average velocity in three ways: most probable velocity (vp), mean velocity (), and root mean square velocity (vrms).

Set the temperature to 200 K (the selected gas should still be Hydrogen).

Estimate the most probable velocity by looking at the peak of the curve. What is your estimate?

Multiple Choice

Based on the shape of the curve, do you think most of the particles are moving faster or slower than the most probable velocity? 

• Faster

• Slower

• Impossible to tell

Open Ended

Predict: The mean velocity is the average velocity of all of the particles. Based on the shape of the curve and your answer to the previous question, do you expect the mean velocity to be greater than or less than the most probable velocity? Explain your reasoning.

Open Ended

Was your prediction correct?

Multiple Choice

Experiment: Try a variety of other gases and temperatures. Is the mean velocity always greater than the most probable velocity?

• Yes

• No

• Impossible to tell

Multiple Choice

Review: A high-temperature gas is compared to the same gas at lower temperature. Which of the following statements is true?

• Every molecule in the high-temperature gas is moving faster than every molecule in the low-temperature gas.

• The average molecular speed in the high-temperature gas is faster than the average molecular speed in the low temperature gas.

• Both statements are true

• Neither statement is true

Multiple Choice

Review: What Celsius temperature is closest to 431 K?

• 150°C

• 250°C

• 450°C

• 700°C

Multiple Choice

The mean particle velocity for a certain gas at a certain temperature is 2,174 m/sec. From the choices below, what is the most likely value for the most probable particle velocity?

• 1,927 m/sec

• 2,174 m/sec

• 2,348 m/sec

• There's no way to determine the answer to this question.