Kinetic Molecular Model of Matter

Question 1

describe the volumes and shapes of all three properties

Answer 1

• 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

Question 2

what happens to the particles in melting ?

Answer 2

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

Question 3

evaporation

Answer 3

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

Question 4

what is the temperature of a gas?

Answer 4

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

Question 5

why does a has exert a pressure on it‘s container?

Answer 5

the particles are moving around very fast and constantly hitting the container walls. this exerts a force on each unit of area: a pressure.

Question 6

what happens if air is pumped out of the container?

Answer 6

the pressure inside is greatly reduced,so the air pressure outside squeezes the container inwards

Question 7

in ______, _______ is _______ to ______

Answer 7

kelvin, pressure, proportional, temperature

Question 8

boyles law

Answer 8

states that at a constant temperature, the volume occupied by a fixed amount of gas is inversely proportional to its pressure

Question 9

what is the formula for boyles law?

Answer 9

v = k/p

where k is a constant

or

inital pressure x initial volume = final pressure x final volume

Question 10

boyles law explained by kinetic theory

Answer 10

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

Question 11

what is brownian motion?

Answer 11

this is the random movement of microscopic particles suspended in liquids or gases resulting from the impact of molecules if the surrounding substance

Question 12

why does a bromine molecule travel faster in a vacuum?

Answer 12

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

Question 13

why do materials expand and contract?

Answer 13

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.

Question 14

why is the amount if increased motion so much larger in gases?

Answer 14

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

Question 15

charles law

Answer 15

states that the volume of a fixed mass of gas is directly proportional to it‘s absolute temperature if the pressure is kept constant

Question 16

how does expansion relate to a liquid in glass thermometer?

Answer 16

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.

Question 17

how does a dig. thermometer work?

Answer 17

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

Question 18

sensitivity

Answer 18

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

Question 19

linearity

Answer 19

the property used for measuring changes by the same amount for every unit of temperature change.

Question 20

accuravy

Answer 20

an accurate thermometer gives correct values of temperature

Question 21

why is a sensitive thermometer not necessarily an accurate one?

Answer 21

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

Question 22

how does a thermocouple work?

Answer 22

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.

Question 23

why can liquids not be compressed?

Answer 23

there is no space in between the particles

Question 24

what is the total mass of a gas?

Answer 24

the sum of the individual molecules

Question 25

gases have a temperature that can be measured

Answer 25

the individual molecules are always moving. the more kinetic energy the have, the higher the temperature of the gas

Question 26

gases have a pressure that can be measured

Answer 26

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

Question 27

what is brownian motion?

Answer 27

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

Question 28

rule for kinetic energy in a gas

Answer 28

the temperature of a gas in kelvins is proportional to the average kinetic energy of the particles

Question 29

• 273 degrees celsius is?

Answer 29

absolute zero. atoms have as little kinetic energy as possible

Question 30

what are the factors necessary for particles to escape a liquid? (evaporation)

Answer 30

• particle travelling in the right direction

- have enough kinetic energy to overcome the attractive forces of the ither particles in the liquid

Question 31

how do gas particles create pressure inside a container?

Answer 31

gas particles collide with the wall of the container, exerting a force on the walls that creates an outward pressure