topic one Flashcards
what are the three states of matter
solid, liquid, gas.
what is plasma
ionised gas mainly found in outer space. it can be referred to as the fourth state
what is kinetic energy
the energy related to the motion or movement of an object.
how are the different physical states characterised
by the different arrangement and movement of the particles. this is dependent on the amount of kinetic energy that the particles possess.
properties of a solid
- particles closely packed
- strong forces between particles, they vibrate around fixed positions
- fixed shape
- fixed volume
properties of a liquid
- particles more spread out
- Weaker forces between particles, they can move past each other
- take the shape of container
- fixed volume
properties of a gas
- particles very spread out
- neglibile forces between particles, they move randomly
- no fixed shape
- no fixed volume
what are changes of state at constant pressure directly related to
change in temperature.
describe the effect of an increase in temperature on a substance
increases the average kinetic energy which means the particles are able to overcome the intermolecular forces that exist between them, which results in a change of state.
what is the process of gas to solid
deposition
what is the process of solid to gas
sublimation
is energy released or absorbed in sublimation
absorbed
is energy released or absorbed in deposition
released
when does the temperature stay constant during a temperature curve
when melting and boiling.
why does temperature stay constant during melting and boiling.
At these points, the energy is being used to overcome the intermolecular forces that exist between the particles.
During melting, the energy input is being used to overcome the intermolecular forces that hold the particles in the solid in fixed positions.
During boiling, the energy input is being used to overcome the intermolecular forces that hold the particles in the liquid together.
what is density
mass per unit volume
density =
mass / volume
what are elements made of
the same kind of atom and cannot be broken down into simpler substances by chemical means
what is an atom
the smallest particle that shows the characteristic properties of that element.
what are metalloids
have the properties of both metals and non metals
elements combine in chemical reactions to make…
compounds
what is a compound
made up of two or more different elements that are chemically combined
sodium chloride is
a white solid
describe hydrogen gas
explosive
describe oxygen gas
highly reactive
define molecule
two or more atoms that are chemically bonded together.
why is NaCl a formula unit
tells us the lowest whole number ratio of the two elements that make up the compound.
homogenous
same composition throughout
heterogenous
non uniform composition
despite homogenous mixtures not being chemically combined
they do not seperate physically on standing
what is air composed of
nitrogen, oxygen, argon
as each component in air has its own boiling point, the gases can be seperated by
fractional distillation
composition of air
nitrogen 78%
oxygen 20.9%
argon 0.93%
carbon dioxide 0.04%
are solutions homogenous or heterogenous
homogenous
what is the concentration of the solution
the amount of solute dissolved in a known volume of a solution
what is the resultant volume
the final volume
what is crude oil
complex mixture of hydrocarbons (compounds containing only carbon and hydrogen)
chemical reactions involve the formation of new
chemical substances
why must the number and dtype of each atom be the same in the reactants and products
due to the conservation of mass.
mass must be conserved in a chemical reaction.
The numbers in front of each formula in a balanced equation are called
stoichiometric coefficients
what do stoichiometric coefficients tell us
the molar ratios of reactants
commmon (s)
Na (s), Mg (s), C (s)
common (l)
H2O (l), Br2 (l)
common (g)
O2 (g), CO2 (g)
common (aq)
NaCl (aq), H2SO4 (aq)
what is a precipitate
an insoluble solid that forms out of a solution
on a relative scale, what is carbon 12 assigned the weight of?
12
what does Ar mean
relative atomic mass, the weighted average mass of an atom compared to 1/12 the mass of an atom of carbon-12.
the mass of 1/12 of an atom of carbon12 is known as an
atomic mass unit
what does a mixture of isotopes make up
any natural sample of an element
an isotope has a different number of
neutrons
how can you analyse the abundance of isotopes of an element
using a mass spectrometer
what is relative atomic mass calculated from
a weighed average that takes into account the existence of different isotopes and their relative abundance.
why is carbon 12 used as a reference
it can be accurately measured and is the most abundant stable isotope of carbon
The relative formula (or molecular) mass (Mr) of a compound is
the weighted average mass of the compound compared to 1/12 the mass of an atom of carbon-12.
why is 1/12 of carbon12 used
each amu is 1, so carbon 12 has 12 amu
what is the mole
the SI unit for the amount of substance (n)
the number of particels in a mole of a substance is numerically equal to the
Avogadro’s constant, 6.02 × 10^23 mol-1
what is molar mass
the mass of one mole of a substance
what is molar mass numerically equal to
relative atomic mass
empirical formula
the lowest whole number ratio of atoms or ions in a compound. a molecular formula is the actual number of atoms in a compound
molecular formula
the actual number of atoms in a compound
when is the empirical formula equal to the molecular
for all ionic compounds
how to calculate empirical formula
from the percentage, divide by molar mass to find the amount in moles. find the simplest whole number ratio.
percentage composition formula
mass of element in compound / molar mass of compound x 100%
empirical formulas can be found experimentally via…
experimental data
water of crystallisation
combustion analysis
when are molar ratios useful
to determine limiting and excess reagents
what is the limiting reactant
limits the amount of product that can be produced.
what is the excess reactant
the amount that remains once the limiting reactant has been consumed in the reaction
when determining limiting and excess reactants, what is divided by what
the amount in moles is divided by the molar ratio/coefficent
what is the theoretical yield
the max amount of product that can be produced assuming that all the limiting reactant has reacted.
what is the actual yield
the amount of product actually produced in a chemical reaction
percentage yield
actual / theoretical x 100%
the kinetic molecular theory of gases
The particles in a gas are in constant, random, straight-line motion.
There are negligible forces of attraction (intermolecular forces) between the particles.
Collisions between particles or with the walls of the container are perfectly elastic (no energy is lost).
The distance between the particles is much greater than the size of the particles, therefore, gas particles have negligible volume.
The kinetic energy of the particles in a gas is directly proportional to the absolute temperature (in kelvin).
the pressure exerted by a gas in a container is determined by how
frequently the particles hit the walls of the container
what is avogadro’s law
equal volumes of gases at the same temperature and pressure contian equal numbers of particles.
molar volume of a gas
This states that one mole of a gas at STP occupies a volume of 22.7 dm3 (22700 cm3 or 0.0227 m3).
relationship between the amount of a gas (in mol) and its volume
amount in mol = vol (dm^3) / molar vol (22.7dm^3)
an ideal gas is
a gas that exhibigts the five postulates of the kinetic molecular theory, as well as obeying gas laws.
what are the gas laws
Boyle’s law, Charles law, Gay-Lussac’s Law
what temperature scale must you use for gas laws
kelvin.
Boyles law
at constant temperature the pressure and volume of a fixed mass of an ideal gas are inversely proportional to each other
Charles Law
at constant pressure the volume of a fixed mass of an ideal gas is directly proportional to its absolute temperature (in kelvin)
Gay-Lussac’s law
at constant volume the pressure of a fixed mass of an ideal gas is directly proportional to its absolute temperature (in kelvin).
Combined gas law:
PV/T = k
P1V1/T1=P2V2/T2
ideal gas equation
PV = nRT
what unit is pressure in the ideal gas equation
pascals
waht unit is volume in the ideal gas equation
m cubed
waht unit is temperature in the ideal gas equation
kelvin
convert cm cubed to m cubed
divide by 10^6
convert dm cubed to m cubed
divide by 10^3
how to convert kPa to Pa
multiply by 10^3
with real gases, some of the assumptions made about ideal gases no longer apply under certain conditions
At very high pressure the gas particles are closer together. Under these conditions, the actual volume of the particles becomes significant.
At low temperatures, the particles move less rapidly (have lower average kinetic energy). This means that there is a greater opportunity for intermolecular forces between the particles to have an effect.
Using the conditions of temperature and pressure at STP, the product of PV/RT for an ideal gas is always equal to
one.
when is the greatest deviation from ideal behaviour seen
when the gas is subjected to a low temperature and a high pressure
why is ideal behaviour deviated from at high pressure
spaces between particles lessen so intermolecular forces operate and particles become attracted to eachother. additionally, the non zero volume of the particles becomes significant in that the volume of a real gas at high pressure is higher than expected and PV/RT > 1.
which gases show the most ideal behaviour
low molar mass and weakest intermolecular forces
units of concentration
include mol dm-3, g dm-3 or parts per million (ppm).
concentration =
concentration (mol dm−3)=amount of solute (mol)volume of solution (dm3)
when would oyu use parts per million
in very dilute concentrations
what is a standard solution
a solution with an accurately known concentration
what is a primary standard solution
it has:
High purity (99.9 %).
High molar mass.
Low reactivity.
Does not change composition in contact with air.
hy should you not use NaOH to make a primary standard solution
it absorbs moisture from the air
what is a secondary standard solution
a solution that has been standardised against a primary standard solution.
what is serial dilution
involves diluting a stock solution multiple times, usually by the same factor, which results in an exponential decrease in concentration.
Continued dilutions will decrease the concentration by a factor of WHAT each time.
ten
volumetric analysis
involves the precise measurement of volumes to calculate the concentration of a solution.
describe a titration
A titration is a method of volumetric analysis in which the concentration of a solution can be determined. In a titration, a burette is filled with a standard solution of known concentration (the titrant). A carefully measured volume of the solution with the unknown concentration (the analyte) is placed in a conical flask below the burette (Figure 2). An indicator is used to determine the end-point of the titration. In acid–base titrations, for example, a suitable indicator is added to the solution in the conical flask and the volume of titrant required to reach the end-point of the titration is recorded. Acid–base titrations are covered in more detail in section 8.2.2.
first trial of a titraion
rough titration. do not use to calculate volume
concordant volumes are
0.10cm cubed within eachother
