[chem] particulate nature of matter

Question 1

what is the kinetic theory of matter

Answer 1

all matter is made up of tiny particles. particles are in constant and random motion (and thus possess kinetic energy), colliding with one another

Question 2

memorise the adam table

Answer 2

refer to notes

Question 3

what is the fundamental difference between solid, liquid and gas

Answer 3

the degree of movement of their particles

Question 4

why do different states of matter have different densities?

Answer 4

for the same substance given the same volume, a gas has fewer particles than a liquid, which in turn has fewer particles than a solid. thus in general, the density of a gas < liquid < solid

Question 5

why will gas exert a pressure on the container?

Answer 5

as the gas particles are in constant and random motion, they will hit the walls of the container, exerting a force on the walls.

Question 6

differences between properties of matter and properties of particles

Answer 6

1. matter may be coloured, particles are not coloured
2. matter can feel hot or cold, the temperature of a substance depends on the kinetic energy of its particles, particles do not get hot or cold
3. matter expands when heated as particles move further apart, particles do not expand when heated, they move faster and further apart

Question 7

what is changing of state?

Answer 7

matter changing from one state to another

Question 8

are changes in state reversible?

Answer 8

yes

Question 9

what are the 7 processes

Answer 9

• boiling
• evaporation
• condensation
• melting
• freezing
• deposition
• sublimation

Question 10

what happens from solid to liquid?

Answer 10

• melting
• melting occurs at fixed temperature
• energy from heating is used to overcome forces of attraction between the particles
• a mixture of solid and liquid exists
• particles do not gain kinetic energy

Question 11

what happens during heating before melting?

Answer 11

• as the solid is heated, particles in solid gain kinetic energy, the temperature of the solid increases until it reaches melting point

Question 12

what happens before boiling?

Answer 12

• all the solid has melted
• temperature of the liquid rises as heating continues
• liquid particles gain kinetic energy

Question 13

what happens before freezing?

Answer 13

• particles in liquid lose kinetic energy
• the temperature of the liquid drops to freezing point

Question 14

what happens during freezing?

Answer 14

• a mixture of liquid and solid exists
• temp remains constant even though cooling continues, because the heat removed during cooling is equal to the heat released by the particles when they take up more orderly arrangement

Question 15

what happens after freezing?

Answer 15

• particles in solid lose kinetic energy
• after all the liquid has frozen, the temp of the solid drops with further cooling

Question 16

what is boiling?

Answer 16

change from a liquid to a gas at the boiling temperature

Question 17

what is evaporation?

Answer 17

the change from a liquid to a gas, below the boiling point

Question 18

differences between boiling and evaporation

Answer 18

boiling: evaporation:
1. fast process, slow process
2. bubbles are observed, no visible change
3. occurs throughout the liquid, occurs at the exposed surface of the liquid only
4. occurs at a fixed temperature, occurs at all temperatures
5. source of energy needed, energy supplied by the surroundings

Question 19

what are volatile liquids

Answer 19

they evaporate quickly at room temperature

Question 20

what’s sublimation

Answer 20

the change from a solid to a gas without melting

Question 21

why will sublimation occur?

Answer 21

the forces of attraction between particles are too weak to remain in the liquid state

Question 22

examples of substances that sublime?

Answer 22

1. iodine
2. ammonium chloride
3. naphthalene
4. solid carbon dioxide (dry ice)

Question 23

what is deposition

Answer 23

the direct solidification of a vapour by cooling

Question 24

what is diffusion

Answer 24

a process whereby the particles move from a region of higher concentration to a region of lower concentration due to constant, random motion of the particles

Question 25

diffusion in gas observation (2 gases in a jar)

Answer 25

(reddish-brown bromine vapour) spread upwards until a uniform (reddish-brown colouration) is seen throughout the gas jars over a period of time

Question 26

diffusion of gas explanation

Answer 26

• both gases are made up of tiny particles moving at constant random motion.
• the gas1 particles diffuse into the spaces between the gas2 particles, and vice versa
• when the ___ colour becomes uniform throughout the gas jar, it means that the particles of both gases are evenly spread
• a homogenous mixture of both gases is formed

Question 27

diffusion in liquid observation (potassium manganate and water)

Answer 27

• a deep purple solution forms at the bottom of the beaker
• diffusion slowly takes place until the solution becomes uniformly purple

Question 28

how to speed up diffusion in liquids involving water? why?

Answer 28

• use warm water
• the solution will become uniformly (purple) within a shorter time, as the rate of diffusion increases as the temperature of the solution increases

Question 29

example of diffusion in solids

Answer 29

• a piece of copper and a piece of nickel tied together firmly and left for an extended period of time
• some copper particles will diffuse into the nickel, and vice versa

Question 30

problem of diffusion in solids? why?

Answer 30

• the process is extremely slow
• the particles in the solid are held closely together in fixed positions by strong forces of attractions

Question 31

how will relative molecular mass affect rate of diffusion?

Answer 31

• gas with lower relative molecular mass will diffuse faster under the same conditions of temperature and pressure

Question 32

how to explain effect of Mr on rate of diffusion?

Answer 32

1. show working for both relative molecular mass
2. __ has lower relative molecular mass than ___, and hence diffuses faster. thus, (product) will form further away from (product with lower Mr)

Question 33

observation of diffusion of gases (porous pot upside down)

Answer 33

• a porous pot containing air is covered with a beaker containing hydrogen
• the level of water in arm A falls initially
• after some time, it rises and returns to the original level

Question 34

explanation for diffusion in gases (porous pot)

Answer 34

1. show working for the 2 Mr of gases
2. explanation
   - as the relative molecular mass of ___ is lower than ____, ___ has diffuses into the porous pot faster than ____ can diffuse out.
   - this results in an increase in the pressure in the porous pot, causing the water level at arm A to fall initially.
   - the water level at A rises to the original level when the concentration of ____ and ____ is the same inside and outside the porous pot, and there is no net diffusion of gases in both directions.