Year 9 Science
end of year revision
Chemistry
Name : _______________________________
What I need to know
atoms : how to work out numbers of
protons, neutrons and electrons using the
periodic table box for an element
How to draw an atom using this information
(the Bohr model) – like the one below
Chromatography
How does it work ? why do some the “spots”
separate on a chromatogram ?
Paper chromatography
Thin layer chromatography - what is it ?
How is it different to paper chromatography ?
The mobile phase and the stationary phase .
Rf values & how to calculate
Isotopes
Same number of protons, different number
of neutrons (so
atomic number is the
same, but atomic mass is different.)
Model of the atom
- how it changed ?
- why it changed over the years ? (new
evidence & ideas)
- The models devised by Dalton,
Thomson, Rutherford, Bohr and
Geiger & Muller
How to calculate the average mass of an
isotope
RFM – calculating relative formula mass of a
molecule using the masses of individual
atoms in the periodic table
CaCO3 = Ca (40) + C (12) + O (3x16) = 100
Separating mixtures :
- distillation
- chromatography
Purity of chemicals
- what does it mean ?
- how does purity affect melting point ?
Metals and alloys
How is a pure metal element different to an
alloy (a mixture of different metals) and why
do we make alloys ?
Particles
How they are arranged in solids, liquids and
gases. How this affects properties ?
What are the changes of state called ?
ions
How atoms become like noble gases (with
full outer shells of electrons). Why they are
charged ? How to work out the charge.
What a giant ionic lattice looks like ?
ionic precipitation
What happens when ionic solids dissolve in
water (free ions). Metals swap partners.
Solids suddenly appear in the solution.
Electrolysis
why molten and dissolved ionic compounds
conduct electricity ? What happens at the
anode & cathode ? Copper chloride solution
(some) Revision Questions:
1] Here is the periodic table box for the metal element Rubidium
a) what is the atomic number of rubidium ?
b)
i) How protons, neutrons and electrons does an atom of Rubidium have ?
ii) why do the electrons in atoms of rubidium stay in orbit around the nucleus …and not
just shoot off into space ?
c) There are 2 common isotopes of rubidium : Rb-85 (72.2%) and Rb-87 (27.8%).
i) How many neutrons does the Rb-87 isotope have ?
ii) Re-calcuate the average atomic mass of Rubidium, given the information about the
2 isotopes in part c.
d) Rubidium is in the same group of the periodic table as lithium and sodium.
How many electrons does it have in its outer shell ?
e) Rubidium reacts with sulphuric acid to form a compound RbSO4
What is the relative formula mass of this compound ? (you can use a periodic table here)
f) Rubidium is a soft metal element with a melting point of 39.4oc. It’s electrical conductivity is
8.3. It does not dissolve in water. Rubidium forms alloys with metals like gold.
i) what is an alloy ?
ii) would the Rb-Au alloy have the same melting point as the element rubidium or a
different one ?
iii) Is the Rb-Au alloy likely to have a higher or lower electrical conductivity than the
element Rubidium ?
iv) The compound RbSO4 dissolves in water, but the element Rb doesn’t. Why ?
g) What would the ionic lattice of solid rubidium sulphate look like ?
(a labelled diagram is a good idea here)
h) Rubidium loses 1 electron when it forms a rubidium ion.
i) why does it lose 1 electron ?
ii) what is the charge on a rubidium ion ?
2] Distillation
a) what would the temperature be on the thermometer ?
b) What would be left behind in the round-bottomed flask after carrying out this experiment ?
c) Does salt water conduct electricity ? Why ?
3] Thin layer chromatography
A
B
a) Which spot/chemical travelled furthest up the TLC plate – A or B ?
b) Which chemical (A or B) was most attracted to the stationary phase (the TLC plate) ?
c) If the solvent front travels 10cm up the plate and spot A travels 8.5cm, calculate the Rf
value for spot A ?