Page 27 - ACE YR IGCSE A TOP APPROACH TO CHEM

Answers

10 C
1 States of Matter In a pressure cooker, electrical energy changes to heat
energy. The heat energy increases the movement of
Part 1: Multiple-choice Questions particles as it gains kinetic energy. The particles collide
more frequently with the walls of pressure cooker and
9 C Penerbitan Pelangi Sdn Bhd. All Rights Reserved.
1 B this increases the pressure in it.
1 – W – Melting is a change from solid to liquid.
2 – X – Water evaporates under the sun. Evaporation is Part 2: Structured Questions
a change from liquid to gas.
3 – Z – Water freezes to form ice cubes in the freezer. 1 (a) (l) [1]
Freezing is a change from liquid to solid. (g) [1]
4 – Y – Condensation is a change from gas to liquid. All particles change from solid to liquid, then from
liquid to gas when the temperature increases.
2 A At region CD, it is a liquid. At region EF, it is a gas.
In liquid state, particles slide past each other. Hand Therefore, at DE, it changes from liquid (l) to gas (g).
sanitiser is in liquid state at room temperature.
(b) The temperaure is above –10°C [1]
3 D and below 80°C. [1]
In solids, particles are closely arranged. In gases, particles The only information can be collected from the
are moving in all directions. So, it is changing from solid question is the starting and ending temperature. It
to gas. is always true that t is above –10°C and below 80°C.
4 A (c) Solid [1]
Gas diffuses. Diffusion is a process where particles move
from a region of higher concentration to a region of (d) The line would not be horizontal. [1]
lower concentration. When durian particles reach the When an impure bromine is used, the melting and
nose, it is detected. boiling points will have a wide range, not a sharp
temperature.
5 C
In gases, particles are arranged randomly and further Temperature / °C
apart. SO is a gas at room temperature. A, B, and D are
2
all solids. 110°C E
100°C
6 D D
For a substance to exist in the liquid state at 35°C, the
melting point should be lower than 35°C, and the boiling C
point should be higher than 35°C. Option D fulfils these
criteria. B
7 A A
Brownian motion is the random movement of particles. Time / minutes
Particles move in a zigzag manner when bombarded
with other unseen tiny particles. Haze particles move in (e) Particles are arranged randomly [1]
a zigzag manner while floating in the air. and far apart. [1]
At region EF, bromine is a gas.
8 B
Condensation is a change from gas to liquid. Energy is 2 (a) (i) A – Boiling [1]
lost to allow particles to move closer together. B – Condensation [1]
(ii) Particles are irregularly arranged [1]
and close together. [1]
Tea particles diffuse from a region of higher
concentration, which is from the tea bag to a region (iii) Any two from: [2]
of lower concentration, which is the water. In the hot • Compressible
water, the particles gain more kinetic energy and move • Takes the shape / volume of its container
faster. After 1 hour, the particles are spread throughout • Easily mixes with other gases
the cup. • Diffuses fast
Or any acceptable physical properties

Answers 139

Answers.indd 139 3/4/22 3:54 PM