S1.1 Flashcards
the particulate nature of matter
atom
def
= the smallest units of matter that still possess certain chemical properties
elementary substances
contain atoms of a single element
elements
def
- = the primary constituents of matter, which cannot be broken down into simpler substances
- made up of the same atoms, or atoms with the same number of protons
- simplest form of matter
- can exist as individual atoms (f.i. Fe) or atoms, which are bonded together (H2)
compounds
def
- consist of atoms of different elements, which are chemically bonded together in a fixed ratio and have different properties from the constituent elements
- constituents cannot be separated using physical methods, only chemical
The composition of matter (A. Einstein)
E = mc^2
E … energy (small value)
m … mass (negligible value)
c … speed of light (large value) = 3.0⋅10^8 ms
division of matter
- pure substances: elements, compounds
- mixtures: homogenous, heterogenous
classifications of matter
- has a mass
- occupies a volume in space
- made up of particles, atoms, molecules or ions
- particles are in constant motion
pure substances
def, division
= matter with definite and constant composition
division: elements, compounds
mixtures
def, division
- = matter, which is a combination of two or more pure substances (in no fixed ratio) that retain their individual properties
- constituents are not chemically bonded, can be separated using physical methods
- division: homogenous, heterogenous
homogeneous mixture
⇒ uniform composition and properties throughout
no visible phases or boundaries
heterogeneous mixture
⇒ non-uniform composition, varying properties throughout
visible phases/boundaries
methods of separation
- filtration
- evaporation
- solvation (dissolution)
- distillation
- paper chromotography
- (re)crystallization
filtration
- = the separation of an insoluble solid from a liquid or solution in a heterogeneous mixture
- filtrate = the liquid/solution which is able to pass through the filter paper
- residue = the insoluble solid which remains on the filter paper
evaporation
- ⇒ the solution is heated in an evaporating dish → the solvent evaporates, leaving the solute behind (as the residue)
- volatile liquids are removed, solids are left
solvation (dissolution)
- = the separation of a heterogeneous mixture of two solids based on differences in solubility, which can be then separated by filtration or evaporation
- soluble substances are removed, insoluble are left
distillation
- = the separation of a liquid mixture based on the difference in volatility or boiling points between the components of the mixture
- volatile liquids are removed, non-volatile ones are left
volatility
= the tendency of a substance to undergo evaporation
paper chromotography
- used to separate a mixture of solutes in a solvent
- mobile phase = solvent undergoing separation
- stationary phase = the chromatography paper used
- the components of the mixture move through the stationary phase at different rates due to their differences in solvation
HPLC
- high pressure/performance liquid chromotography
- mobile phase is liquid
- faster
- only a small sample is needed
crystallization
def, based on
- = the process of forming solid crystals from a solution
- based on the varied solubilities of solids at different temperatures
recrystallization
def, based on
- = a separation technique, which is used to remove impurities that are mixed in with a solid
- based on the varied solubilities of solids at different temperatures
methodology of recrystallization
- dissolve the impure mixture in a volume of hot solvent that is just enough to completely dissolve it ⇒ insoluble impurities can be filtered off
- the solution is cooled to room temperature which causes the solubility of the dissolved solids to decrease ⇒ formation of crystals, leaving the soluble impurities in the solution, which are then filtered to obtain the pure product
cover with a watch glass in order to prevent evaporation and contamination
kinetic molecular theory
- all matter is made up of small particles
- all particles have kinetic energy ⇒ they are all constantly moving
- the amount of kinetic energy is proportional to the temperature of the substance ⇒ particles have greater motion at higher temperatures
- collisions between particles are elastic (no loss of kinetic energy)
states of matter
solid
liquid
gas
plasma
solids
kin energy, space between particles, V, shape, f of attr., density
- least amount of kinetic energy
- particles are very close together with little space between them ⇒ cannot be compressed
- fixed V, shape
- strong forces of attraction between particles
- particles vibrate in fixed positions but do not move around
- tend to have higher density
liquid
particle placement, f of attr., V, shape
- particles are close together with some space between them ⇒ can flow, move more freely
- forces of attraction exist, yet are weaker than in a solid
- fixed V, no fixed shape ⇒ take the shape of the bottom of the container
- cannot be compressed
- particles vibrate, rotate and move around
p(H2O)
density
1 g/cm^3
1000 kg/m^3
gasses
V, shape, f of attr, particle placement, kin energy
- no fixed V or shape ⇒ take on the same shape of the container itself, can be compressed
- attractive forces between particles are negligible
- particles are far apart with lots of space between them
- most amount of kinetic energy
- particles vibrate, rotate, and move around faster than in a liquid
plasma
- = ionized gas mostly found in space
- atoms in plasma become increasingly ionized
- free electrons move among positively charged ions
endothermic phase changes
- melting (solid to liquid)
- vaporization (liquid to gas)
- sublimation (solid to gas)
absorb energy/heat => to break bonds
exothermic phase changes
- freezing (liquid to solid)
- condensation (gas to liquid)
- deposition (gas to solid)
release energy/heat => to form stronger bonds
vaporization vs boiling vs evaporation
- vaporization ⇒ the general process of a liquid becoming a gas and can happen through evaporation and boiling
- evaporation ⇒ only at the surface of a liquid; doesn’t have to reach the boiling point
- boiling ⇒ throughout the liquid
- at a specific temperature; when vapor pressure reaches external pressure
Kelvins
- SI unit of temperature
- absolute zero ⇒ the movement of all particles stops (T = 0K = -273°C)
- T(K) = T(°C) + 273.15
