Unit 3: Topic 5 - Kinetic Molecular Theory Flashcards
What is the kinetic molecular theory?
The kinetic molecular theory (KMT) relates the macroscopic properties of gases to the motions of the particles in the gas. The Maxwell-Boltzmann distribution describes the distribution of the kinetic energies of particles at a given temperature.
The kinetic molecular theory describes the behavior of an ideal gas. It states that:
1) The gas particles have almost no volume (negligible).
2) Particles exert no force on each other. They experience elastic collisions in which total kinetic energy is conserved.
3) Gas particles move in constant, random, straight-line motion.
4) There is negligible intermolecular force due to the distance between the particles.
5) The average kinetic energy is proportional to the temperature of the gas. (This will be represented by the Maxwell-Boltzman distribution curve)
What does the equation KE = 1⁄2 mv2 tell us?
The equation KE = (1⁄2) mv^2 relates speed to kinetic energy, where all the particles in a sample of matter are in continuous, random motion.
m is mass, KE is kinetic energy, v is velocity
Kinetic energy is directly proportional to velocity (speed). If velocity doubles, kinetic energy quadruples since velocity is squared.
What is the relationship of temperature, in Kelvin, to the average kinetic energy of particles in a sample?
The temperature of a sample of particles is directly proportional to the average kinetic energy.
As temperature increases, so does the kinetic energy. If the temperature doesn’t change, neither will the kinetic energy.
Ex: Hydrogen gas at 200K will have double the average kinetic energy of those at 100K.
What is the Maxwell-Boltzmann distribution?
The Maxwell-Boltzmann distribution shows the distributions of energy among the particles in a sample of gas at a given temperature.
Note: The X-axis is speed, while the Y-axis is the number of molecules that have that speed.
The highest point on the curves means that there are more molecules moving at that speed.
The maximum of the cold curve shows that the majority of molecules have slower speeds. On the other hand, the maximum on the hot curve shows that the majority of the molecules have higher speeds. This should make sense because hotter molecules move faster.
