Gases Flashcards
two factors that determine the state of a substance
- the forces holding the particles tother
- the kinetic energy of the particles
ionic forces
- intramolecuclar
- usually solid state
- NaCl
Polar (dipole-dipole) forces
- intermolecular
- can be anything, usually liquid or gas
- HCL (g)
Dispersion force
- intermolecular
- liquid or gas
- CO2 (g)
What is the kinetic molecular theory?
all substances contain entities that are in constant motion
3 types of entity motion
- vibrational
- rotational
- translational
what particles have a vibration motion?
all particles
what particles have a rotational motion?
- liquids
- solids
- some solids
what particles have a translational motion?
- only in liquids and gases
temperature definition
a measure of the average kinetic energy of the entities of a substance
What is the kinetic molecular theory?
- the volume of an individual gas moecule is negligible
- there are no attractive nor repulsive forces between gas molecules
- gas molecules move randomly in all directions, in straight lines
- when gas molecules collide, they don’t loose kinetic energy
- ideal gases, do not condense into liquids when cooled
- the average kinetic energy of a gas molecule is directly related to the temperature. The greater the temperature, the greater the average motion of the molecules and the greater their kinetic energy
KMT describes a hypothetical gas called an ideal gas
i deal particles take up hardly any space
Who came up with kinetic molecular theory?
Robet Brown
pressure definition
the force exerted on an object per unit of surface area (P = F/A)
common SI unit of measurement of pressure
the pascal Pa = 1N/m^2
how is the pressure of a gas determined
by the kinetic moition
what device is used to measure pressure
a barometer
Describe the mercury barometer
- a closed tube is filled with mercury, then inverted into a pan
- gravity pulls the mercury downwards, but pressure pushes on the mercury in the pan, keeping it inside the tube
- the result is that we can measure the height of the Hg( mm) in the tube as a measure of pressure
mass of atmosphere
5.1 * 10^18 kg
= 1000 kg over an area of 1 m^2
Why is there lower pressure the higher up in the atmosphere you are?
there is lass atmosphere above, less atmosphere pushing down