E s s e n t i a l C h e m i s t r y f o r C a m b r i d g e I G C S E ® 2 nd E d i t i o n
Unit 1 Particles and purification
SUMMARY QUESTIONS:
1 (a) The random movement of molecules resulting in the mixing up of different particles.
(b) The change from liquid to vapour state below the boiling point of the liquid.
(c) The change of state from a gas to a liquid.
(d) The separation of a liquid from a mixture of liquids by boiling the mixture and condensing
the vapours.
2 Solid – has a definite shape + particles only vibrate
Liquid – particles close together + can flow, but has definite surface
Gas – particles move everywhere + particles far apart
3 Volumetric flask: can be used to make up to 500 cm3 of a solution accurately
Measuring cylinder: can be used to measure out approximately 20 cm3 of a solution
Burette: can be used to measure out 18.5 cm3 of a liquid accurately
Beaker: can be used to mix two solutions
Condenser: used to change a vapour back to a liquid
4 Draw a pencil line on a rectangular piece of filter paper 1 cm from bottom
↓
Place a small drop of dye mixture on the line and allow to dry
↓
Place filter paper in a beaker of solvent so solvent level is below the line
↓
Allow solvent to run up the paper
↓
Remove filter paper before solvent level has reached the top and mark solvent level
5 (a) More air particles are being pushed in and they exert a force (due to their constant
movement) on the balloon.
(b) The particles are fixed in position and cannot move.
(c) The particles in a liquid are already close together and they cannot be pushed together any
more (unless a much greater force is applied).
PRACTICE QUESTIONS:
1 C Burette
2 D Distillation
3 (a) (i) Slight red colour in the liquid around the crystal.
(ii) The solution is evenly coloured throughout.
(b) (i) Arrangement: Particles in a fixed position / regular;
Motion: none / only vibrate / don’t move
(ii) Arrangement: random / irregular / no particular arrangement;
Motion: random / slide over each other
(c) Evaporate some of the water; leave to crystallise; filter off crystals / pick out crystals and dry
on filter paper
© OUP 2015: this may be reproduced for class use solely for the purchaser’s institute
E s s e n t i a l C h e m i s t r y f o r C a m b r i d g e I G C S E ® 2 nd E d i t i o n
4 (a) (i)
(ii)
(iii)
(b) (i)
Melting
Evaporating
Condensing
Melting and (ii) Evaporating
Particles absorb energy to overcome (weak) forces holding them in solid or liquid.
NOT: between atoms.
(c) Arrangement: random / no particular arrangement / irregular;
Motion: random / move everywhere / rapid.
5 (a) Refer to Figure 1.4.2
Filter paper dipping into solvent in beaker; base line on filter paper above solvent level;
drop of substance to be spotted on line.
(b) (i) On the base line
(ii) C
(iii) B
(iv) A
6 (a) (i)
Any two of:
Particles of liquid gain energy / forces between particles weaken / particles with most
energy escape (as a gas).
(ii) Move randomly / in all directions; so spread everywhere / collide with air particles.
(b) Methylamine particles move faster / HCl particles move more slowly; because methylamine
is a lighter molecule / HCl is a heavier molecule (greater relative molecular mass).
(c) (i) Further to the right / near the HCl end
(ii) Ammonia has lower relative molecular mass / lighter molecules than methylamine;
so diffuses faster.
7 (a) 4
(b) Top spot marked with an ‘M’.
(c) 0.8
(d) Use a different solvent / use two-dimensional paper chromatography
(e) Spray with locating agent / named locating agent; warm to develop the colour
8 (a) Brownian Motion
(b) Graphite particles do not move on their own (fixed position); water is a liquid and so its
particles move randomly and slide past each other; this random movement causes them
to collide with the graphite particles bombarding them; the graphite particles are not
bombarded equally on all sides; causing them to move in a random irregular way.
9 (a) Set up the apparatus as shown in the picture with carbon dioxide inside the porous pot so
that the coloured water levels are equal either side of the tube; put the porous pot inside
the hydrogen container and allow the gases to diffuse; observe the change in level of the
coloured water which should rise in the right arm of the tube.
(b) Hydrogen particles have a lower relative molecular mass than carbon dioxide; they will
diffuse faster into the porous pot than the carbon dioxide diffuses out; this means there
will be more particles of gases in the pot, which will increase the pressure on the liquid,
in turn making the level of coloured water rise in the right hand side of the tube.
© OUP 2015: this may be reproduced for class use solely for the purchaser’s institute