Page 22 - Ranger PT3 2022 science

Science PT3 Chapter 5 Water and Solution

K L
Measuring Results:
cylinder
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Carbon Measuring Volume of
electrodes cylinder collected gas (ml)
Water + dilute
hydrochloric K 10
acid
L 20
Switch + –
Discussion:
(a) Gas that is collected at anode (measuring cylinder K) lights up a glowing
wooden splinter. This shows the existence of oxygen.
(b) Gas that is collected at cathode (measuring cylinder L) extinguishes
a burning wooden splinter and produces a ‘pop’ sound. This shows the
presence of hydrogen.
(c) The ratio of the volume of gas produced at anode to the gas produced at
cathode is 1 : 2.
(d) A little dilute hydrochloric acid is added to increase the conductivity of
electricity.

Effects of Impurities on the Physical Characteristics of Water
1. The presence of impurities substance in water can alter the physical characteristics
of water.
(a) Effect on the boiling point and melting point
Thermometer
Conical flask
Thermometer
Distilled water + Form 2
Salt
Form 2
Ice + Salt
Bunsen
Towel
burner
Diagram 5.4
• The presence of salt can either increase the boiling point of water or
decrease the melting point of ice.
(b) The presence of impurities alter the density of the water as well. Beside that,
the taste, smell and colour too might change due to the presence of impurities.

Evaporation of Water
1. Evaporation of water is a process where liquid changes into gas which happens
on the water surface at any temperature.
2. The experiment below aims to investigate the factors that influence the rate of
evaporation of water.

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05 Ranger Science Ting.2.indd 153 30/03/2022 1:57 PM