Answers to Sec 3
Sci (Chem)
Discover Chemistry
Workbook Page 1 - 9
Page 1
Arrangement of particles (in solids): closely packed and
vibrate about fixed position
Arrangement of particles (in liquids): slide over each
other and move around randomly
Liquid  Freezing  Solid
Gas  Condensation  Liqiud
Gas  Condensation  Solid
Arrangement of particles (in gas): spread far apart and
move randomly at great speed
Page 2
1. D (Matter can be found in space, in non –
living things and may not be solid)
2. A (Gas does not have fixed volume)
3. B (Learn how to draw the arrangement of
particles in the three states)
4. B (heat absorbed increases kinetic energy)
Page 3
1. D (Biggest difference between melting and
boiling point, gives the largest range of being a
liquid)
2. A (because its melting point is below 30 oC)
3. C (During condensation, gas particles loses
kinetic energy, move closer together and forms
back the liquid structure)
4. D (solid  Sublimation  gas)
Page 5 / 6
a) A – B : Melting
C – D: Boiling
E – F: Condensation
G – H: Freezing
b) Physical state of methanal: Gas
Physical state of selenium: Solid
c) About 700 oC. Selenium will turn into gas
(vaporize) around this temperature.
Page 6 / 7
1. C (iodine sublimes)
2. B (see graph)
3. D (particles fixed in position  particles close
together and move freely: solid  liquid: Melting)
4. B (Bromine is liquid at temperatures between
melting point –7 oC and boiling point 59 oC)
5. C (X  liquid, Y  gas, X between – 95 and 70
oC,
Y above 70 oC)
6. B ( Boiling water  100 oC, L is liquid at room
temp, Boiling point of L between room temp and
100 oC)
Page 7 / 8
7ai)
State of M: Gas
7aii) State of N: Liquid
7bi)
A could be water. Its melting point is 0 oC
and its boiling point is 100 oC, which are
the same as those of water.
7bii) All the substances have melting points
below room temperature and boiling points
above room temperature. Therefore they are
liquids at room temperature.
7biii) D
Page 8 / 9
8a)
Chlorine monoxide
8b)
It would start to boil and change to gaseous form.
8c)
Chlorine monoxide and sulphur dioxide
8d)
Chlorine monoxide
Page 9
9a)
The particles of a gas are moving randomly at
great speed and eventually bump onto the
wall of the container. As a result, the gas
exerts pressure on the walls of its container.
9b)
An increase in temperature causes the particles
to move faster. The particles therefore bump
onto the wall of the container more frequently.
As a result, the pressure is increased.