Page 148 - Chemistry_Form_2

Chemistry
for Secondary Schools

5. Explain the advantages of the following types of salts in real-life applications
by providing two examples for each:
(a) Deliquescent salts
(b) Efflorescent salts
(c) Hygroscopic salts
FOR ONLINE READING ONLY

Project: Determination of pH values of natural and synthetic substances

Collect samples of various substances such as tap water, bottled water, river
water, fruits juices, and soaps and detergents. Determine the pH values using
natural and synthetic acid-base indicators, litmus papers, or pH meter. Write
a detailed report outlining the methodology, materials used, observations,
results, discussions, and conclusions regarding the pH properties of the
substances. Then, prepare a brief presentation summarising the experiments,
results and key learnings. Enhance the presentation with visuals such as
photos of the tests or a pH chart derived from the collected data.

Chapter summary

1. An acid is a chemical substance which produces hydrogen ions (H ) in
+
water as the positively charged ions.

2. A base refers to a chemical substance which, when dissolved in water,
–
produces hydroxide ions (OH ) as negatively charged ions. It is also
defined as a metal oxide or hydroxide which neutralises an acid. An alkali is
a soluble base.
3. A strong acid or strong base dissociates completely in water. A weak acid
or weak base dissociates partially in water.
4. A pH indicator is a chemical substance that exhibits different colours in
solutions of different acidities or alkalinities.

5. The basicity of an acid is the number of hydrogen atoms per molecule of
the acid that can be displaced by a metal in a solution. An acid that has
only one hydrogen atom that can be displaced is said to be monobasic. An
acid with a basicity of two is dibasic, while the one with basicity of three
is tribasic.

Student’s Book Form Two 141

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CHEMISTRY FORM TWO NEW 2025 DUMMY.indd 141