science end of chemistry test Flashcards
what is the definition of an atom
the smallest neutral part of an element that can take part in chemical reactions
what is the definition of an element
made up of one type of atom
what is the definition of a compound
different types of elements that are chemically combined
what is the definition of a molecule
two or more elements joined together
what is the definition of a mixture
two or more substances/elements/compounds that are not chemically combined. can be separated
what is the definition of chemical change
when a reaction occurs between two or more substances to create a new chemical
what is the definition of physical change
a change where no new substances are formed
what is chromotography
used to separate mixtures of coloured compounds. separated based on density, lower the density the further it travels up the paper
what is magnetism
used to separate magnetic metals from non-magnetic substances
what is crystallisation
used to separate dissolved salts from their solvent. heating the solution evaporates the the solvent leaving the salt crystals
what is a separating funnel
used to separate immiscible liquids. opening the tap on the funnel allows the less dense bottom layer to flow through. tap can be closed when top layer reaches bottom
what is filtration
used to separate insoluble solids from liquids, solid residue left in filter paper and filtrate passes through
what is simple distillation
used to separate miscible liquids based on different boiling points. liquid with lower boiling point boils first and gas passes down condenser, cools and condenses again
what is fractional distillation
liquids will evaporate and rise up the column, liquid with the highest boiling point will condense on beads and drip back down while lowest boiling point will rise and pass into the condenser
who developed the atom in 460bc
democritus
what did democritus do
first to have the idea that everything was made of particles called atoms
who developed the atom in 1803
john dalton
what did john dalton do
he described atoms as like billiard balls and said atoms of the same element were identical. thought they could not be split
who developed the atom in 1897
jj thomson
what did jj thomson do
discovered the electron by passing high voltage electricity through gases. proposed the plum pudding model of atom, ball of positive charge with negative electrons embedded in it
who developed the atom in 1909
rutherford and marsden
what did rutherford and marsden do
fired positive alpha particles at a thin gold foil, expected all to pass through, some deflected and others bounced back. plum pudding model ditched for nuclear model, positive nucleus surrounded by negative atoms
who developed the atom in 1912
niels bohr
what did niels bohr do
agreed with the nuclear model and suggested that electrons orbited at specifiic distances. we call these shells
who devloped the atom in 1920
ernest rutherford
what did ernest rutherford do
suggested the name proton for hydrogen nuclei
who developed the atom in 1932
james chadwick
what did james chadwick do
proved the existence of the neutron and measured its mass
what is the radius of an atom
0.1nm
what proportion of a nucleas is that of an atom
1/10,000
how do you convert nm to m
multiple by 10^-9
how do you convert m to nm
divide by 10^-9
what are isotopes
atoms of the same element with the same number of protons and electrons but different numbers of neutrons
how do you work out relative atomic mass
total mass of all atoms of that element / total number of atoms of that element
what are the rules of electronic structure
always fill the shell from the centre
first shell can hold 2 electrosn
second can hold 8
third can hold 8 before the fourth starts to fill up
who developed the periodic table in 1817
johann döbreiner
what did john döbreiner do
noticed groups of elements of similar properties so put forward his law of triads. examples were lithium, sodium and potassium
who developed the periodic table in 1864
john newlands
what did john newlands do
ordered elements by atomic mass and noticed patterns every 8 elements so he proposed law of octaves. ideas were rejected order went wrong after calcium , unreactive copper in the same group as reactive lithium, sodium and potassium
who developed the periodic table in 1869
dmitri mendeleev
what did dmitri mendeleev do
also ordered elements by atomic mass but left gaps for elements that hadn’t yet been discovered. swapped order of some elements so that properties fit the pattern. mendeleev didn’t know about subatomic particles, we now know he put in order of atomic number. mendeleev’s table didn’t contain noble gases because they hadn’t been discovered
how reactive are noble gases and why
they are unreactive because they have a full shell of outer electrons and don’t want to lose or gain any electrons
how does density change with noble gases
increases as you go down the group
how does boiling point change with noble gases
increases going down the group, more weak forces of attraction so more energy is required to break them apart
how does lithium react with water
fizzes and floats
how does sodium react with water
fizzes, floats, melts and sometimes a yellow flame is seen
how does potassium react with water
fizzes, floats, melts and burns with a lilac flame
word equation for alkali metal in water
metal + water –> metal hydroxide + hydrogen
symbol equation for alkali metal in water
2Li + 2H⬇️20 –> 2LiOH + H⬇️2
word equation for alkali metal with oxygen
metal + oxygen –> metal oxide
symbol equation for alkali metal with oxygen
4Li + O⬇️2 –> 2Li⬇️2O
word equation for alkali metal with chlorine
metal + chlorine –> metal chloride
symbol equation for alkali metal with chlorine
2Li + Cl⬇️2 –> 2LiCl
How do alkalis change as go down the group and why
They get more reactive because their outer electron is further away meaning it can be lost easier
What is an ion
A charged particle that has either lost or gained an electron
What ions do alkalis metals form
A +1 ion
What is fluorine
A pale yellow gas
What is chlorine
A pale green gas
What is bromine
A dark brown liquid
What is iodine
A grey solid with purple vapours
How do halogens exist as
Diatonic molecules e.g. F⬇️2
Word equation for halogen with hydrogen
Halogen + hydrogen –> hydrogen halide
Symbol equation for halogen with hydrogen
Cl⬇️2 + H⬇️2
–> 2HCl
Word equation for halogens with metals
Halogen + metal
–> metal halide
Symbol equation for halogens with metals
Cl⬇️2 + 2Na –> 2NaCl
What takes place during a halogen displacement reaction
A colour change
What displaces what in a halogen reaction
A more reactive halogen displaces a less reactive one to form a compound
How does reactivity change as you go down the halogens and why
They become less reactive because it is harder to gain an electron
what is the order of reactivity for halogens
fluorine > chlorine > bromine > iodine
example of word halogen displacement reaction
chlorine + sodium bromide –> sodium chloride + bromine
example of symbol halogen displacement reaction
Cl⬇️2 + 2NaBr –> 2NaCl + Br⬇️2
what type of ion do halogens form
a -1 ion because they all gain 1 electron
melting point of transition and alkali metals
transition metals have high, alkali metals have low
density of transition and alkali metals
transition metals have high, alkali metals have low
physical structure of transition and alkali metals
transition metals are strong and hard, alkali metals are soft
reactivity of transition and alkali metals
transition have low reactivity, alkali metals have high
types of ions of transition and alkali metals
transition metals react to form ions with different charges, alkali metals react to form +1 ions
compounds of transition and alkali metals
transition metals form coloured compounds, alkali metals form white ones
what is a property that only transition metals have
they act as catalysts
what properties do transition and alkali metals have in common
- good conductors of heat
- good conductors of electricity
- shiny
do transtion metals react with oxygen and chlroine like alkali metals do
yes but more slowly
word equation for a metal reacting with oxygen
metal + oxygen –> metal oxide
symbol equation for a metal reacting with oxygen
2Cu + O⬇️2 –> CuO
word equation for a metal reacting with chlorine
metal + chlorine –> metal chloride
symbol equation for a metal reacting with chlorine
2Fe + 3Cl⬇️2 –> 2FeCl⬇️2
