Kinetic Molecular Model of Matter Flashcards
describe the volumes and shapes of all three properties
- solid: fixed shape, fixed volume, not easily compressed
liquid: assumes the shape of the part of the container that it occupies, is not easily compressed, fixed volume
gas: assumes the shape and volume of it‘s container, occupies the whole volume, compressible
what happens to the particles in melting ?
when the material is heated, the vibrations if the particles increases to the point at which the forces are no longer strong enough to hold tve structure together in the rigid order of a solid. the bonds are not broken, just weakened
evaporation
when a particle breaks away from the surface of a liquid and forms a gas
this reduces the average kinetic energy of the molecules remaining in the liquid, and so the temperature of the liquid falls
what is the temperature of a gas?
it is a measure of the average kinetic energy of the molecules in the gas. therefore, it is related to the velocity of the molecules
why does a has exert a pressure on it‘s container?
the particles are moving around very fast and constantly hitting the container walls. this exerts a force on each unit of area: a pressure.
what happens if air is pumped out of the container?
the pressure inside is greatly reduced,so the air pressure outside squeezes the container inwards
in ______, _______ is _______ to ______
kelvin, pressure, proportional, temperature
boyles law
states that at a constant temperature, the volume occupied by a fixed amount of gas is inversely proportional to its pressure
what is the formula for boyles law?
v = k/p
where k is a constant
or
inital pressure x initial volume = final pressure x final volume
boyles law explained by kinetic theory
if the volume of a fixed gas is halved by halving the volume of tje container, you would expect the pressure to double because tjer would be twice as many particles in each unit of volume. this would result in twice as many collisions with the container walls, and so, twice the oressure
what is brownian motion?
this is the random movement of microscopic particles suspended in liquids or gases resulting from the impact of molecules if the surrounding substance
why does a bromine molecule travel faster in a vacuum?
they don‘t bump into air particles along the way, which would result kn a transfer of kinetic energy, causing the bromine molecules to rebound. in a vacuum, the molecules can move unrestrictedly
why do materials expand and contract?
kinetic theory tells us that particles in solids and liquids are in constant vibration. they vibrate faster after heating and force each other a little further apart so the material takes up more space.
why is the amount if increased motion so much larger in gases?
the particles afe moving quickly in all directions - so the relative expansion is much greater.
likewise, liquids expand more than solids, as the particles are able to move, unlike in solids where they can only vibrate about fixed positions
charles law
states that the volume of a fixed mass of gas is directly proportional to it‘s absolute temperature if the pressure is kept constant
how does expansion relate to a liquid in glass thermometer?
it uses the fact that tje coloured liquid expands when its temperature increases and contracts when it decreases, meaning the top if the liquid moves up or down the tube which has a calibrated scale on it.
how does a dig. thermometer work?
the resistance if the metal probe varies with temperature, so that changing the current in the circuit (which will habe been calibrated in advance such that a certain current corresponds with a certain temperature
sensitivity
a thermometer is sensitive when it gives a large response to a small change in temperature
it can be increased by using a material that expands more during temperature chance, or by decreasing the diameter of the liquid thread inside the glass
linearity
the property used for measuring changes by the same amount for every unit of temperature change.
accuravy
an accurate thermometer gives correct values of temperature
why is a sensitive thermometer not necessarily an accurate one?
if the scale has been incorrectly marked or if the measuring property varies in a non linear manner, the readings from the this sensitive thermometer will not be accurate
how does a thermocouple work?
the thermocouple is based on the fact that any two metals in contact generate a tiny voltage.
to measure this voltage with a voltmeter, the two metals need to form a circuit, which means there must be two junctions. when the junctions are at the same temperature, there will be no voltage, because they cancel out: but when the junctions are at different temperatures, difference between the two voltages can be measured using a voltmeter.
one junction is placed at a point where the temperature is measured. the other is kept at room temperature.
why can liquids not be compressed?
there is no space in between the particles
what is the total mass of a gas?
the sum of the individual molecules
gases have a temperature that can be measured
the individual molecules are always moving. the more kinetic energy the have, the higher the temperature of the gas
gases have a pressure that can be measured
when the molecules hit the wall of the container, they exert a force on it
it is the total force divided by the surface area of the container that we observe when measuring gas pressure
what is brownian motion?
the random movement of particles
particles are constantly being hit by fast-moving particles which are too small to see.
large, massive particles -> moved by light, fast-moving particles
the gas molecules are moving randomly in all directions but the resultant force on each smoke particle is not zero
rule for kinetic energy in a gas
the temperature of a gas in kelvins is proportional to the average kinetic energy of the particles
- 273 degrees celsius is?
absolute zero. atoms have as little kinetic energy as possible
what are the factors necessary for particles to escape a liquid? (evaporation)
- particle travelling in the right direction
- have enough kinetic energy to overcome the attractive forces of the ither particles in the liquid
how do gas particles create pressure inside a container?
gas particles collide with the wall of the container, exerting a force on the walls that creates an outward pressure
