[chem] particulate nature of matter Flashcards
what is the kinetic theory of matter
all matter is made up of tiny particles. particles are in constant and random motion (and thus possess kinetic energy), colliding with one another
memorise the adam table
refer to notes
what is the fundamental difference between solid, liquid and gas
the degree of movement of their particles
why do different states of matter have different densities?
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
why will gas exert a pressure on the container?
as the gas particles are in constant and random motion, they will hit the walls of the container, exerting a force on the walls.
differences between properties of matter and properties of particles
- matter may be coloured, particles are not coloured
- 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
- matter expands when heated as particles move further apart, particles do not expand when heated, they move faster and further apart
what is changing of state?
matter changing from one state to another
are changes in state reversible?
yes
what are the 7 processes
- boiling
- evaporation
- condensation
- melting
- freezing
- deposition
- sublimation
what happens from solid to liquid?
- 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
what happens during heating before melting?
- as the solid is heated, particles in solid gain kinetic energy, the temperature of the solid increases until it reaches melting point
what happens before boiling?
- all the solid has melted
- temperature of the liquid rises as heating continues
- liquid particles gain kinetic energy
what happens before freezing?
- particles in liquid lose kinetic energy
- the temperature of the liquid drops to freezing point
what happens during freezing?
- 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
what happens after freezing?
- particles in solid lose kinetic energy
- after all the liquid has frozen, the temp of the solid drops with further cooling
what is boiling?
change from a liquid to a gas at the boiling temperature
what is evaporation?
the change from a liquid to a gas, below the boiling point
differences between boiling and evaporation
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
what are volatile liquids
they evaporate quickly at room temperature
what’s sublimation
the change from a solid to a gas without melting
why will sublimation occur?
the forces of attraction between particles are too weak to remain in the liquid state
examples of substances that sublime?
- iodine
- ammonium chloride
- naphthalene
- solid carbon dioxide (dry ice)
what is deposition
the direct solidification of a vapour by cooling
what is diffusion
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
diffusion in gas observation (2 gases in a jar)
(reddish-brown bromine vapour) spread upwards until a uniform (reddish-brown colouration) is seen throughout the gas jars over a period of time
diffusion of gas explanation
- 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
diffusion in liquid observation (potassium manganate and water)
- a deep purple solution forms at the bottom of the beaker
- diffusion slowly takes place until the solution becomes uniformly purple
how to speed up diffusion in liquids involving water? why?
- 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
example of diffusion in solids
- 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
problem of diffusion in solids? why?
- the process is extremely slow
- the particles in the solid are held closely together in fixed positions by strong forces of attractions
how will relative molecular mass affect rate of diffusion?
- gas with lower relative molecular mass will diffuse faster under the same conditions of temperature and pressure
how to explain effect of Mr on rate of diffusion?
- show working for both relative molecular mass
- __ has lower relative molecular mass than ___, and hence diffuses faster. thus, (product) will form further away from (product with lower Mr)
observation of diffusion of gases (porous pot upside down)
- 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
explanation for diffusion in gases (porous pot)
- show working for the 2 Mr of gases
- 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.
