1 Principles of Chemistry Flashcards
what are the 3 states of matter
solid, liquid, gas
arrangement of a solid
has least energy – particles are not moving/are just vibrating and they are arranged regularly and very closely together and all touching
arrangement of a liquid
particles have more energy than those in a solid, but less than those in a gas and the particles are closer together but have a random arrangement
arrangement of a gas
particles have the most energy – as the particles are the most spread apart with a random arrangement
what is melting
solid -> liquid
increase in particle energy
what is boiling
liquid -> gas
increase in particle energy
what is freezing
liquid -> solid
decrease in particle energy
what is evaporation
liquid -> gas (at surface)
increase in energy
what is condensation
gas -> liquid
decrease in energy
what is sublimation
solid -> gas
increase in energy
what is deposition
gas -> solid
decrease in energy
how does melting occur
The process requires heat energy which transforms into kinetic energy, allowing the particles to move.
It occurs at a specific temperature known as the melting point which is unique to each pure solid
how does boiling occur
This requires heat which causes bubbles of gas to form below the surface of a liquid, allowing for liquid particles to escape from the surface and from within the liquid
It occurs at a specific temperature known as the boiling point which is unique to each pure liquid
how does freezing occur
This is the reverse of melting and occurs at exactly the same temperature as melting, hence the melting point and freezing point of a pure substance are the same
It requires a significant decrease in temperature (or loss of thermal energy) and occurs at a specific temperature which is unique for each pure substance
how does evaporation occur
Evaporation occurs only at the surface of liquids where high energy particles can escape from the liquid’s surface at low temperatures, below the boiling point of the liquid
The larger the surface area and the warmer the liquid/surface, the more quickly a liquid can evaporate
Evaporation occurs over a range of temperatures, but heating will speed up the process as particles need energy to escape from the surface
how does condensation occur
When a gas is cooled its particles lose energy and when they bump into each other, they lack energy to bounce away again, instead grouping together to form a liquid
what is diffusion
The random movement of particles from a high to low concentration
why does diffusion occur slower in a liquid than a gas
Diffusion in liquids is slower than in gases because the particles in a liquid are closely packed together and move more slowly
why does the colour get paler when a solution is diluted
when you add water the evenly spaced particles become much more spread out making the colour paler
solvent
the liquid in which something is dissolved in
eg the water in sea water
solute
the substance which is dissolved in something to form a solution
eg salt in sea water
solution
the mixture of solvent and dissolved solute
eg sea water
saturated solution
a solution with the maximum concentration of solute dissolved in the solvent
soluble
something that will dissolve in a specific liquid
eg salt is soluble in water
insoluble
something that will not dissolve in a specific liquid
eg sand in water
what is solubility normally expressed as
Solubility can be expressed in g per 100 g of solvent
for example 10g of salt can dissolve (before it gets saturated) in 100g of water which means the solubility is 10g/100g
if something is given not out of 100g then it must be converted
eg 10g/50g = 20g/100g
what is solublility
Solubility is a measurement of how much of a substance (solute) will dissolve in a given volume of a liquid (solvent)
what do solubility curves represent
Solubility graphs or curves represent solubility in g per 100 g of solvent with different temperature
what does above the solubility line mean
above the line means the solute will no longer dissolve
what does the solubility line mean
the solution is saturated
what does below the solubility line mean
the solute will dissolve
1.7C practical - investigate the solubility of a solid in water at a specific temperature
- set a water bath to a specific temperature (eg 50c)
- measure out 100g of water into a beaker
- place the beaker in the water bath
- add a thermometer to the beaker and once it has reached the same temperature as the water bath
- add a known mass of solid and stir until it has dissolved
- keep adding known masses in increments until not more dissolves
- write down what mass of solid that was added before solution got saturated
whats an element
a substance made up of the same atoms
eg a beaker containing all carbon
whats a compound
a substance made up of 2 or more elements chemically joined
eg a beaker containing water (H2O)
what a mixture
a substance made up of 2 or more elements not chemically bonded
eg a beaker containing O2 and N2 but they aren’t joined to each other
why does a pure substance have a fixed melting point
there is only 1 type of thing in it so it will all have the same melting point
eg water boils at 100c
how to distinguish between a pure substance and a mixture
slowly heat the substance up as a pure substance will boil at one temperature whereas the mixture will boil of a range of temperatures
what does simple distillation separate
a liquid and soluble solid from a solution (e.g., water from a solution of salt water) or a pure liquid from a mixture of liquids
simple distillation method
- heat the solution
- the thing with the lower boiling point will evaporate first leaving the other substance
eg in a water and ethonal mixture, the ethanol would evaporate first leaving the water
- if you want to keep both substances use a simple distillation set up (a delivery tube surrounded with cold water, to recondense the evaporated substance, leading into a beaker)
what does fractional distillation separate
This is used to separate two or more liquids that have different boiling points which are mixed together
fractional distillation method
- heat the solution
- the thing with the lower boiling point will evaporate first leaving the other substances
eg in a water, ethanol and methanol mixture, the methanol would evaporate first leaving the ethanol and water
- if you want to keep all substances use a simple distillation set up (a delivery tube surrounded with cold water, to recondense the evaporated substance, leading into a beaker)
what does filterisation seperate
an undissolved solid from a mixture of the solid and a liquid / solution (eg sand from a mixture of sand and water)
filtration method
- place a piece of filter paper in a funnel
- place the funnel above a beaker
- pour the substance through the funnel
the liquid will be in the beaker and the solid will be left in the filter paper
what does crystallisation separate
a dissolved solid from a solution, when the solid is much more soluble in hot solvent than in cold solvent
crystallisation method
- heat the solution which allows any excess solvent (liquid) to evaporate
- once the ruffly half the solution has evaporated
- remove from heat to allow cooling
- crystals will appear of the solute that was dissolved
what is a atom
a single particle of an element
eg one carbon
what is a molecule
2 or more atoms chemically joined together to form
where is a proton found
in the nucleus
where is a neutron found
in the nucleus
where is an electron found
orbiting the nucleus in shells
relative mass of a proton
1
relative mass of a neutron
1
relative mass of a electron
1/1840
charge of a proton
+1
charge of a neutron
0
charge of an electron
-1
what is the atomic number
number of protons an atom has
eg the atomic number of carbon is 6
what is the mass number
the sum of the number of protons and neutrons in an atom
eg carbons mass is 12
what is an isotope
an atom with the same number of protons and electrons but a different number of neutrons
what is the RAM (relative atomic mass or Ar)
the weighted average mass of an atom of an element, compared to 1/12th the mass of a carbon 12 atom
how to find the number of electrons in an element
same as the atomic number
how to find the number of neutrons in an element
mass number - the atomic number
how to calculate RAM (Ar) from isotope abundance
( % of isotope A x mass of isotope A ) + ( % of isotope B x mass of isotope B ) / 100
how are the elements arranged in the periodic table
in the order of atomic number
in groups and periods
what does a group tell you
the number of electrons in the outer shell of the elements
what does a period tell you
how many electron shells an element has
what is the number of outer shell electrons in a metal
1-3
what is the number of outer shell electrons in a non-metal
4-8
how to tell a metal or non-metal based on electrical conductivity
metals are good electrical conductors
non-metals are poor electrical conductors
what forms when metals react with water
a base
what forms when nonmetals react with water
an acid
how to split the periodic table into metals and nonmetals
zigzag line going down right between boron and aluminium
why do elements in the same group react in the same way
they all have the same number of electrons in the outer shell ad it is the outer shell of electrons that react
why don’t the noble gasses react
atoms with a full outer shell are stable
they have a full outer shell of electrons so they don’t need to react to achieve a full outer shell
what is a mole
a unit for a substance
what is the difference between the relative formula mass (Mr) and relative atomic mass (Ar)
the Mr is the mass of the a whole molecule whereas the Ar is the mass of an atom
how to calculate the Mr of a molecule from the Ar’s of the atoms in the molecule
add up the masses of each of the atoms
the big numbers do not apply
small numbers apply only to the element that they are behind
everything in a bracket is multiplied by the small number outside the bracket
for water (h2O)
H= 1 x 2 = 2 (1 is the mass of hydrogen and times by 2 because there is 2 hydrogen’s in water)
0= 16 x 1 = 16
2+16 = 18
1 mol =
6.022 x 10 ^23 atoms / molecules
mass, moles and Ar/Mr formula
moles = mass / Ar or Mr
how to calculate reacting masses
- balance the symbol equation if not alr
- calculate the moles from mass given
- work out the ratio of substances (using the
large numbers) - convert moles to mass
how to calculate percentage yield
actual yield / theoretical yield x 100
how to experimentally find the formula for metal oxides
- measure mass of crucible and lid
- measure a mass of the metal and add
into the crucible - heat strongly and lift the occasionally
- every 5 minutes remove from heat and
reweigh - once mass stops increasing stop heating
- calculate metal oxide weight by:
final mass - mass of crucible and lid
to find the formula:
- work out the mass of the metal and the
oxygen individually - work out the moles of the metal and the
oxygen individually - divide both moles by the smallest mole
how to experimentally find the formula for water / hydrated salts
(water of crystallisation)
- measure mass of evaporating basin
- measure a mass of hydrated salt and add
into the evaporating basin - heat strongly until the salt turns completely
white - reweigh the crucible and white salt
- calculate anhydrous salt weight by:
the basins mass and white salt - just the
basin - calculate the mass of water lost by:
hydrated salt mass - unhydrated salt mass
to find the formula:
- find mass of the water and the mass of the
unhydrated salt - work out the Mr of the salt and water
individually - work out the moles of the salt and the
water individually - divide both moles by the smallest mole
what is the molecular formula
shows the number and type of each atom in a molecule
what is the empirical formula
simplest whole number ratio of the atoms of each element of a compound
how to calculate the empirical formula
- work out the moles of each atom in the
molecule - divide both sets of moles by the smallest
mole - if the answer contains a 0.5 then times all
by 2
how to determine the formula of a metal oxide by combustion
- measure mass of crucible and lid
- measure a mass of the metal and add
into the crucible - heat strongly and lift the lid occasionally
- every 5 minutes remove from heat and
reweigh - once mass stops increasing stop heating
- calculate metal oxide weight by:
final mass - mass of crucible and lid
then calculate the empirical formula
how to determine the formula of a metal
oxide by reduction
- Measure mass of the empty boiling tube
- Place metal oxide into a horizontal boiling tube and measure the mass again
- Support the tube in a horizontal position held by a clamp
- A steady stream of natural gas(methane) is passed over the copper(II)oxide and the excess gas is burned off
- The copper(II)oxide is heated strongly using a Bunsen burner
- Heat until metal oxide completely changes colour, meaning that all the oxygen has been removed
- Measure mass of the tube with remaining metal powder and subtract the mass of the tube to work out mass of metal
to work out empirical formula:
- work out mass of oxygen by
mass of metal oxide - metal - then work out empirical formula
how are ions formed
by the loss or gain of electrons
what is the charge of a metal ion in group 1
1+
what is the charge of a metal ion in group 2
2+
what is the charge of a metal ion in group 3
3+
what is the charge of a nonmetal ion in group 5
3-
what is the charge of a nonmetal ion in group 6
2-
what is the charge of a nonmetal ion in group 7
1-
what is the charge of a Ag ion
1+
what is the charge of a Cu(II) ion
2+
what is the charge of a Fe(II) ion
2+
what is the charge of a Fe(III) ion
3+
what is the charge of a Pb ion
2+
what is the charge of a Zn ion
2+
what is the charge of a hydrogen ion
1+
what is the charge of a hydroxide (OH) ion
1-
what is the charge of a ammonium (NH4) ion
1+
what is the charge of a carbonate (CO3) ion
2-
what is the charge of a nitrate (NO3) ion
1-
what is the charge of a sulfate (SO4) ion
2-
what is an ion
atoms which do not have an equal number of protons and electrons
how to write formulas for ions which bond to form compounds
charges must cancel out to equal 0 as compounds are uncharged
so Li (1+) and O (2-) create Li2O
ionic bonding definition
the electrostatic force of attraction between 2 oppositely charged ions
why do compounds with giant ionic lattices have high melting and boiling points
strong electrostatic forces acting between the oppositely charged ions
These forces act in all directions and a lot of energy is required to overcome them giving them a high melting and boiling point
when do ionic compounds conduct electricity
in an aqueous solution or when molten as the ions have more energy and are able to move
not as a solid as there are no free ions to move
how is a covalent bond formed
nonmetal atoms sharing pairs of electrons
covalent bond definition
the electrostatic force of attraction between the nuclei and a shared pair of electrons
why are substances with simple molecular formulas liquids or gases or solids with low boiling points
the covalent forces between atoms are strong but the inter-molecular forces connecting each molecule are weak
the weak inter-molecular forces are easy to overcome (require a low temperature to break) meaning at room temperature the bonds are broken and therefore are liquids or gases or solids with a low boiling points
why do giant covalent structures have a higher melting point then simple molecular ones
to melt giant covalent bonds you must break the strong covalent bonds whereas melting a simple molecular structure only requires overcoming the weak intermolecular forces
why does the melting points of simple molecular structures increase as the relative molecular mass increases
the increase in mass means there will also be more electrons and therefore there are more intermolecular forces of attraction that need to be overcome which increases the melting point
why do giant covalent structures have a high melting point
As lots of covalent bonds are present in the compound and not many weak intermolecular bonds (which are easy to overcome and require low heat)
the covalent bonds are very hard to overcome which means as there are lots of them it takes a very high temperature to overcome
do covalent compounds conduct electricity
no as there are no free electrons to move
how does the structure of diamond influence its physical properties including electrical conductivity and hardness
giant covalent structure
very hard as in order to break you have to break the strong covalent bonds
does not conduct electricity because there are no free electrons or ions
high melting and boiling point
definition of a metallic bond
the electrostatic force of attraction between the delocalised free moving electrons and the positive metal ions
what is the strength of the attraction in a metallic bond determined by
the charge of the metal ions and by how many electrons there are
how does the structure of graphite influence its physical properties including electrical conductivity and hardness
giant covalent structure
arranged in layers where there are weak intermolecular forces in between the layers however there are layers themselves are bonded covalently which means the layers can slide over each other
high melting and boiling point
soft and slippery
can conduct as it has declocalized electrons
used as a lubricant
why do metals have a high boiling point and melting point
the electrostatic forces of attraction are very strong meaning it takes lots of energy to overcome giving them high melting and boiling points
what is a metallic bond
a group of metal atoms all donate their outer shell electrons into a delocalised sea of electrons (which can move freely throughout the structure) which then forms positive metal ions
the negatively charged sea of electrons attracts the positively charged ions bonding the metals
how does the structure of bucminster fullerene influence its physical properties including electrical conductivity and hardness
simple molecular structure
low melting and boiling points as it has weak intermolecular forces so easy to overcome
it is also soft for the same reason
it can conduct as there are delocalised electrons
used as a lubricant or a drug delivery system
why do metals conduct so well
have a large sea of delocalised electrons that are free to move and conduct
why are metals malleable
when a force is applied instead of breaking or shattering, the ions move and are reshaped
if any gaps are made in the structure when the force is applied, the delocalised electrons will move and fill in the gaps and therefore retain the structure and keep the properties
chromatography method
Use a ruler to draw a horizontal pencil line (as a pens ink would run into the other samples) 2 cm from the end of the chromatography paper
Use a different capillary tube to put a tiny spot of each colouring A, B, C and D on the line
Use the fifth tube to put a small spot of the unknown mixture U on the line
Make sure each spot is no more than 2-3 mm in diameter and label each spot in pencil
Pour water into the beaker to a depth of no more than 1 cm (to avoid the samples washing into the solvent container) and clip the top of the chromatography paper to the wooden spill. The top end is the furthest from the spots
Carefully rest the wooden spill on the top edge of the beaker. The bottom edge of the paper should dip into the solvent
Allow the solvent to travel undisturbed at least three quarters of the way up the paper
Remove the paper and draw another pencil line on the dry part of the paper as close to the wet edge as possible. This is called the solvent front line
Measure the distance in mm between the two pencil lines. This is the distance travelled by the water solvent
For each of food colour A, B, C and D measure the distance in mm from the start line to the middle of the spot
calculate the Rf values for each one. Compare the Rf values from the known samples to the unknown dye to see what it is composed of
how to calculate Rf value
Rf = distance travelled by substance / distance traveled by solvent
These values are used to identify the components of mixtures
The Rf value of a particular compound is always the same but it is dependent, however, on the solvent used
If the solvent is changed then the value changes
Calculating the Rf value allows chemists to identify unknown substances because it can be compared with Rf values of known substances under the same conditions
These values are known as reference values
The Rf value will always lie between 0 and 1; the closer it is to 1, the more soluble is that component in the solvent
what does a chromatogram do
This technique is used to separate substances that have different solubilities in a given solvent (e.g., different coloured inks that have been mixed to make black ink)
An impure substance will show up with more than one spot, a pure substance should only show up with one spot
how to represent a metal lattice by a 2D diagram
large regular arrangement of circles with + inside then much smaller circles in the gaps between them with -
why do covalent compounds not conduct
electricity is the flow of charged particles and in covalent structures there are no freely moveble charged particles to carry current
why do ionic compounds only conduct when molten or in an aqueous solution
They cannot conduct electricity in the solid state as the ions are in fixed positions within the lattice and are unable to move but when molten or in solution the particles become free to move as the lattice is broken down.
what is a cation
positively charged ion
what is a anion
negatively charged ion
moles equation in a liquid
moles = volume x concentration
moles in a gas equation
moles = volume / 24(decimeters)
