• Describe how the kinetic-molecular theory is used to explain how gases behave at different temperatures. (Exploration 1) • Analyze data that shows how gas particle mass affects that gas’s behavior. (Exploration 2) • Describe the Maxwell-Boltzmann Distribution. (Explorations 1 and 2)
Description of Activity
The kinetic-molecular theory states that a collection of gas molecules’ average kinetic energy has a specific value at any given temperature. In this activity, you will study how temperature and gas particle mass affect the frequency distribution of gas particle speeds. You will examine and analyze speed frequency distribution graphs. This distribution is called the Maxwell-Boltzmann Distribution.
Jump Start
1. What is kinetic energy? • Kinetic energy is the production of energy by an object in motion. There are three subcategories of kinetic energy, including vibration, caused by objects vibrating; rotational, caused by moving objects; and translational, caused by objects hitting one another.
2. What is thermal energy? • Thermal energy is the energy a substance or system has related to its temperature, the energy of moving or vibrating molecules. Atoms and molecules, the smallest particles of any substance, are always in motion. The motion of thermal energy is usually not visible, but we can feel or see its effects. We use thermal energy to cook our food and heat our homes, and we use it to generate electricity.
3. What happens to a gas’s thermal energy as that gas’s temperature increases? • Increase in volume of a material as its temperature is increased.
4. What happens to the average speeds of the particles in a gas when one increases that gas’s temperature? • The average particle speed increases.
Safety Discussion
If you conduct this experiment in a laboratory setting, be aware that gases heated in a closed container could result in the container exploding.
Exploration 1: The Effect of Temperature on Gas Behavior
Procedure 1. Choose any gas from the list box. 2. Set Temperature to any value. Observe the shape of the frequency distribution of speeds graph. Sketch this graph. Record the most probable particle speed (vp) and the average particle speed (vavg) in Table 1. 3. Repeat step 2 for four additional temperatures. Increase the value each time. 4. Choose another gas and repeat steps 2 and 3.
