Edexcel IGCSE Chemistry Chapter 1, page 5 ANSWERS
1.
a) melting
b) freezing
c) sublimation
d) deposition or reverse sublimation
2.
solid
liquid
gas
a)
b)
Particles in a solid vibrate
about a fixed point, so
they do not move
around.
Particles in a liquid vibrate and
can move from their position.
Particles in a liquid will take
the shape of their container.
c) In boiling, there is more energy in the whole system –the forces of attraction are broken between all
particles. In evaporation only those particles at the surface sometimes break free and escape.
d) The seal must prevent particles from escaping from the container. Then they are in a confined space,
so they have nowhere to go.
3.a) A = gas, B = liquid, C = solid, D = liquid, E = solid
b) C, because it takes the most heat energy to break the forces of attraction
c) A, because it requires very little energy for it to melt and boil.
d) A, the only one that is gas
e) it does not boil, it sublimes. Its melting point and boiling point are the same.
f) D, it’s boiling point is closer to 20C
4. a) The reactants must first diffuse along the length of the tube. The reaction takes place when the
reactants meet.
b) The particles will move faster
c) The temperature of a substance is a reflection of the energy of its particles. Gas particles have kinetic
energy because they are moving. Air particles at 2C are moving more slowly than air particles at 25C. If
we measure the temperature of the gas we are heating, it will take longer to reach the same
temperature when we begin with the gas at 2C, than with the gas initially at 25C.
Edexcel IGCSE Chemistry Chapter 1, page 5 ANSWERS
d) Chloride particles are more massive than ammonia particles (look at the Periodic Table for the atomic
masses of chlorine, nitrogen and hydrogen), so they diffuse more slowly than the lighter ammonia
particles during the same time period.
e) ammonium bromide
f) the ring will for even closer to the hydrogen bromide end of the tube than when hydrochloric acid was
used.
5. This will have to be a fair test, so you will alter only one variable – the coloured solution. All other
conditions of the experiment must remain identical. Each coloured solution will act as a control for the
other.