Students should learn Students should be able to a. Introduction to acids and alkalis
common acids and alkalis in daily life and in the laboratory
characteristics and chemical reactions of acids as illustrated by dilute hydrochloric acid and dilute sulphuric acid
acidic properties and hydrogen ions (H+(aq))
role of water in exhibiting properties of acid
basicity of acid
characteristics and chemical reactions of alkalis as illustrated by sodium hydroxide and aqueous ammonia
alkaline properties and hydroxide ions (OH(aq))
corrosive nature of concentrated acids and concentrated alkalis
recognise that some household substances are acidic
state the common acids found in laboratory
describe the characteristics of acids and their typical reactions
write chemical and ionic equations for the reactions of acids
relate acidic properties to the presence of hydrogen ions (H+(aq))
describe the role of water for acids to exhibit their properties
state the basicity of different acids such as HCl, H2SO4, H3PO4, CH3COOH
define bases and alkalis in terms of their reactions with acids
recognise that some household substances are alkaline
state the common alkalis found in the laboratory
describe the characteristics of alkalis and their typical reactions
write chemical and ionic equations for the reactions of alkalis
relate alkaline properties to the presence of hydroxide ions (OH(aq))
describe the corrosive nature of acids and alkalis and the safety precautions in handling them b. Indicators and pH
acid-base indicators as exemplified by litmus, methyl orange and phenolphthalein
pH scale as a measure of acidity and alkalinity
pH = log[H+(aq)]
use of universal indicator and an appropriate instrument to measure the pH of solutions
state the colours produced by litmus, methyl orange and phenolphthalein in acidic solutions and alkaline solutions
describe how to test for acidity and alkalinity using suitable indicators
relate the pH scale to the acidity or alkalinity of substances
perform calculations related to the concentration of H+(aq) and the pH value of a strong acid solution
suggest and demonstrate appropriate ways to
Students should learn Students should be able to c. Strength of acids and alkalis
meaning of strong and weak acids as well as strong and weak alkalis in terms of their extent of
dissociation in aqueous solutions
methods to compare the strength of acids/alkalis
describe the dissociation of acids and alkalis
relate the strength of acids and alkalis to their extent of dissociation
describe acids and alkalis with the appropriate terms: strong and weak, concentrated and dilute
suggest and perform experiments to compare the strength of acids or alkalis
d. Salts and neutralisation
bases as chemical opposites of acids
neutralisation as the reaction between acid and base/alkali to form water and salt only
exothermic nature of neutralisation
preparation of soluble and insoluble salts
naming of common salts
applications of neutralisation
write chemical and ionic equations for neutralisation
state the general rules of solubility for common salts in water
describe the techniques used in the preparation, separation and purification of soluble and insoluble salts
suggest a method for preparing a particular salt
name the common salts formed from the reaction of acids and alkalis
explain some applications of neutralisation
e. Concentration of solutions
concentration of solutions in mol dm3 (molarity)
convert the molar concentration of solutions to g dm3
perform calculations related to the concentration of solution
f. Volumetric analysis involving acids and alkalis
standard solutions
acid-alkali titrations
describe and demonstrate how to prepare solutions of a required concentration by dissolving a solid or diluting a concentrated solution
calculate the concentrations of the solutions prepared
describe and demonstrate the techniques of performing acid-alkali titration
apply the concepts of concentration of solution and use the results of acid-alkali titrations to solve stoichiometric problems
communicate the procedures and results of a volumetric analysis experiment by writing a laboratory report
Suggested Learning and Teaching Activities
Students are expected to develop the learning outcomes using a variety of learning experiences. Some related examples are:
searching for examples of naturally occurring acids and bases, and their chemical composition.
investigating the actions of dilute acids on metals, carbonates, hydrogencarbonates, metal oxides and metal hydroxides.
designing and performing experiments to study the role of water in exhibiting properties of acids.
searching for information about the hazardous nature of acids/alkalis.
investigating the action of dilute alkalis on aqueous metal ions to form metal hydroxide precipitates.
investigating the action of dilute alkalis on ammonium compounds to give ammonia gas.
performing experiments to investigate the corrosive nature of concentrated acids/alkalis.
searching for information about the nature of common acid-base indicators.
performing experiments to find out the pH values of some domestic substances.
measuring pH values of substances by using data-logger or pH meter.
designing and performing experiments to compare the strengths of acids/alkalis.
performing an experiment for distinguishing a strong acid and a weak acid having the same pH value.
investigating the temperature change in a neutralisation process.
preparing and isolating soluble and insoluble salts.
searching for and presenting information on applications of neutralisation.
preparing a standard solution for volumetric analysis.
performing calculations involving molarity.
performing acid-alkali titrations using suitable indicators/pH meter/data-logger.
using a titration experiment to determine the concentration of acetic acid in vinegar or the concentration of sodium hydroxide in drain cleaner.
performing calculations on titrations.
writing a detailed report for an experiment involving volumetric analysis.
Values and Attitudes
Students are expected to develop, in particular, the following values and attitudes:
to develop a positive attitude towards the safe handling, storage and disposal of chemicals, and hence adopt safe practices.
to appreciate the importance of proper laboratory techniques and precise calculations for obtaining accurate results.
to appreciate that volumetric analysis is a vital technique in analytical chemistry.
to appreciate the importance of controlling experimental variables in making comparisons.
to appreciate the use of instruments in enhancing the efficiency and accuracy of scientific investigation.
STSE Connections
Students are encouraged to appreciate and comprehend issues which reflect the interconnections of science, technology, society and the environment. Related examples are:
Measures involving neutralisation have been implemented to control the emission of nitrogen oxides and sulphur dioxide from vehicles, factories and power stations.
Caustic soda is manufactured by the chloroalkali industry which is a traditional chemical raw materials industry.
Volumetric analysis, as an essential technique in analytical chemistry, is applied in testing laboratories and forensic science.
Antacid is a common drug which contains base(s) for neutralising stomach acid and therefore relieving stomach ache.