Gen 4 - Phases Flashcards
What is a phase ?
A phase (or state of matter) is a uniform, distinct and usually separable region of material.
What is the triple point ?
The temperature and pressure at which all 3 phases of a substance can coexist.
Describe the 3 phases/states
- Gaseous
- Solid
- Liquid
Define the Gaseous phase
A substance in the Gaseous phase has neither fixed volume or fixed shape; it spreads itself uniformly throughout any container in which it is placed.
What are the four fundamental properties in which any given gas can be describe ?
- Mass
- Temperature
- Volume
- Pressure
Define standard temperature and pressure
Volume of a gas is usually reported at:
0ºC (273.15 Kelvin)
1.00 atm (101.33kPa, 760mmHg, 760 Torr)
Define pressure in terms of chemical phases
Force per unit area
What is the SI unit of standard pressure ?
101.33 kPa
What is the standard molar volume of a gas ?
The volume occupied by one mole of any gas at STP, equal to 22.4L.
What are the first 3 points of the kinetic molecular theory of gases ?
- Gases are composed of extremely small particles, separated by distances that are relatively large in comparison to particle diameter.
- Particles are in constant motion, except when they collide with one another
- Particles of an ideal gas exert no atractive or repulsive force on one another
What is an ideal gas ?
A gas that exactly fits the kinetic molecular theory of gases
What are the fourth and fifth princples of the kinetic molecular theory of gases ?
- Collisions of the particles with the walls of the container result in no loss of energy when they collide, energy is transferred and particles change direction.
- The average KE increases in direct proportion to the temperature. The typical speed of a gas particle is directly proportional to the square root of the absolute temperature.
What is kinetic energy in relation to particles ?
How would you calculate KE in relation to Gases ?
What is the pressure in a Vacuum ?
A Vacuum is completely devoid of particles and thus has no pressure.
Which four properties of a gas can be measured experimentally ?
- Weight - from which we can calculate (N), No. od molecules/atoms present
- Pressure (P) exerted on walls of the container
- Volume (V) occupied by the gas
- Temperature (T) of the gas
Sketch and explain the Maxwell distribution plot
- At a higher temperature, the curve peak is flattened, which means gas particles in the sample are travelling at a wider range of velocities.
- More particles are above the minimum escape KE required to evaporate
What does Graham’s law describe ?
The average free path of any typical gas particle taken per unit volume. These are known as Diffusion and Effusion.
What is diffusion in relation to gases ?
The flow of gas particles from an area of high concentration to low concentration. Lighter particles diffuse more quickly than heavier particles.
What is Effusion in relation to gases ?
The movement of a gas through a small hole or pore into another gaseous region, or into a vacuum.
(NB. If the hole is large enough, diffusion may happen instead)
How would you calculate rates of diffusion and effusion in gases ?
Explain Charles’ law in relation to gases
The volume (V) of a gas is directly proportional to the absolute temperature (K) when Pressure (P) and Number of particles (N) are constant.