chapter 13 states of matter 13.1 the nature of gases
TRANSCRIPT
Chemistry
Today we are learning to:-
1. Describe the kinetic theory of gases
2. Interpret gas pressure in terms of the kinetic theory
3. Define the relationship between the Kelvin temperature scale
and average kinetic energy
The kinetic theory states:
1. Particles of a gas are assumed to be small, hard spheres with an
insignificant volume.
2. The motion of the particles in a gas is rapid, constant, and random.
3. Collisions between particles in a gas are perfectly elastic.
The Kinetic Theory of Gases
The energy an object has because of its motion is called kinetic energy.
The kinetic theory states that all matter consists of tiny particles that are in
constant motion.
Gas Pressure
Gas pressure results from the force exerted by a gas per unit surface area of an
object.
Empty space with no particles and no pressure is called a vacuum.
Atmospheric pressure results from the collisions of atoms and molecules in air
with objects.
Gas pressure is the result of simultaneous collisions of billions of rapidly moving
particles in a gas with an object.
The SI unit of pressure is the Pascal (Pa).
One standard atmosphere (atm) is the pressure required to support 760 mm
of mercury in a mercury barometer at 25°C.
Gas Pressure
for Sample Problem 13.1
1. What pressure in kilopascals and in atmospheres, does a gas exert at 385 mm
Hg?
2. The pressure at the top of mount Everest is 33.7 kPa. Is that pressure greater
than or less than 0.25 atm?
3. What pressure in mm Hg and atm, does a sample of neon gas exert at 75.0
kPa?
Gas Pressure
Kinetic Energy and Temperature
Atoms or molecules at a given temperature have
i. a wide range of kinetic energies.
ii. most have kinetic energies somewhere in the middle of this range.
Average kinetic energy is therefore used to describe motion of particles
in a substance
At a given temperature all substances have the same average kinetic
energy
Kinetic Energy and Temperature
There is a relationship between the average kinetic energy of atoms or
molecules in a sample and its temperature.
Higher kinetic energy means higher temperatures.
Average Kinetic Energy
Absolute zero (0 K, or –273°C) is the temperature at which the motion of
particles theoretically ceases.
Particles would have no kinetic energy at absolute zero.
Absolute zero has never been produced in the laboratory.
0K = -273°C
The temperature in Kelvin of a
substance is directly proportional to the
average kinetic energy of the particles
of the substance.
13.1 Section Quiz.
1.According to the kinetic theory, the particles in a gas • are attracted to each other.• are in constant random motion.• have the same kinetic energy.• have a significant volume.
13.1 Section Quiz.
2. The pressure a gas exerts on another object is caused by • the physical size of the gas particles.• collisions between gas particles and the
object.• collisions between gas particles.• the chemical composition of the gas.
13.1 Section Quiz.
3. The average kinetic energy of the particles in a substance is directly proportional to the• Fahrenheit temperature.• Kelvin temperature.• molar mass of the substance.• Celsius temperature.