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I Planet Earth

Overview

The natural world is made up of chemicals which can be obtained from the earth’s crust, the sea and the atmosphere. The purpose of this topic is to provide opportunities for students to appreciate that we are living in a world of chemicals and that chemistry is a highly relevant and important area of learning. Another purpose of this topic is to enable students to recognise that the study of chemistry includes the investigation of possible methods to isolate useful materials in our environment and to analyse them. Students who have completed this topic are expected to have a better understanding of scientific investigation and chemistry concepts learned in the junior science curriculum.

Students should know the terms “element”, “compound” and “mixture”, “physical change”

and “chemical change”, “physical property” and “chemical property”, “solvent”, “solute”

and “saturated solution”. They should also be able to use word equations to represent chemical changes, to suggest appropriate methods for the separation of mixtures, and to undertake tests for chemical species.

Students should learn Students should be able to a. The atmosphere

 composition of air

 separation of oxygen and nitrogen from liquid air by fractional distillation

 test for oxygen

 describe the processes involved in fractional distillation of liquid air, and understand the concepts and procedures involved

 demonstrate how to carry out a test for oxygen

Students should learn Students should be able to b. The ocean

 composition of sea water

 extraction of common salt and isolation of pure water from sea water

 tests to show the presence of sodium and chloride in a sample of common salt

 test for the presence of water in a sample

 electrolysis of sea water and uses of the products

 describe various kinds of minerals in the sea

 demonstrate how to extract common salt and isolate pure water from sea water

 describe the processes involved in evaporation, distillation, crystallisation and filtration as

different kinds of physical separation methods and understand the concepts and procedures involved

 evaluate the appropriateness of using evaporation, distillation, crystallisation and filtration for different physical separation situations

 demonstrate how to carry out the flame test, test for chloride and test for water

c. Rocks and minerals

 rocks as a source of minerals

 isolation of useful materials from minerals as exemplified by the extraction of metals from their ores

 limestone, chalk and marble as different forms of calcium carbonate

 erosion processes as exemplified by the action of heat, water and acids on calcium carbonate

 thermal decomposition of calcium carbonate and test for carbon dioxide

 tests to show the presence of calcium and carbonate in a sample of limestone/chalk/marble

 describe the methods for the extraction of metals from their ores, such as the physical method, heating alone and heating with carbon

 describe different forms of calcium carbonate in nature

 understand that chemicals may change through the action of heat, water and acids

 use word equations to describe chemical changes

 demonstrate how to carry out tests for carbon dioxide and calcium

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 information on issues related to the atmosphere, such as air pollution and the applications of the products obtained from fractional distillation of liquid air.

using an appropriate method to test for oxygen and carbon dioxide.

performing experiments and evaluating methods of physical separation including evaporation, distillation, crystallisation and filtration.

using appropriate apparatus and techniques to carry out the flame test and test for chloride.

performing a test to show the presence of water in a given sample.

doing problem-solving exercises on separating mixtures (e.g. a mixture of salt, sugar and sand, and a mixture of sand, water and oil).

extracting silver from silver oxide.

investigating the actions of heat, water and acids on calcium carbonate.

designing and performing chemical tests for calcium carbonate.

participating in decision-making exercises or discussions on issues related to conservation of natural resources.

describing chemical changes using word equations.

Values and Attitudes

Students are expected to develop, in particular, the following values and attitudes:

to value the need for the safe handling and disposal of chemicals.

to appreciate that the earth is the source of a variety of materials useful to human beings.

to show concern over the limited reserve of natural resources.

to show an interest in chemistry and curiosity about it.

to appreciate the contribution of chemists to the separation and identification of chemical species.

STSE Connections

Students are encouraged to appreciate and comprehend issues which reflect the interconnections of science, technology, society and the environment. Related examples are:

Oxygen extracted from air can be used for medicinal purposes.

Methods involving chemical reactions are used to purify drinking water for travellers to districts without a clean and safe water supply.

Desalination is an alternative means of providing fresh water to the Hong Kong people rather than importing water from the Guangdong province.

Mining and extraction of chemicals from the earth should be regulated to conserve the environment.

Products obtained by the electrolysis of sea water are beneficial to our society.

II Microscopic World

Overview

The study of chemistry involves the linkage between phenomena in the macroscopic world and the interaction of atoms, molecules and ions in the microscopic world. Through studying of the structures of atoms, molecules and ions, and the bonding in elements and compounds, students will acquire knowledge of some basic chemical principles. These can serve to further illustrate the macroscopic level of chemistry, such as patterns of changes, observations in various chemical reactions, the rates of reactions and chemical equilibria. In addition, students should be able to perform calculations related to chemical formulae, which are the basis of mole calculations to be studied in later topics.

Students should also be able to appreciate the interrelation between bonding, structures and properties of substances by learning the properties of metals, giant ionic substances, simple molecular substances and giant covalent substances. With the knowledge of various structures, students should be able to differentiate the properties of substances with different structures, and to appreciate that knowing the structure of a substance can help us decide its applications.

Through activities such as gathering and analysing information about atomic structure and the Periodic Table, students should appreciate the impact of the discoveries of atomic structure and the development of the Periodic Table on modern chemistry. Students should also be able to appreciate that symbols and chemical formulae constitute part of the common language used by scientists to communicate chemical concepts.

Students should learn Students should be able to a. Atomic structure

 elements, atoms and symbols

 classification of elements into metals, non-metals and metalloids

 electrons, neutrons and protons as subatomic particles

 simple model of atom

 atomic number (Z) and mass number (A)

state the relationship between element and atom

use symbols to represent elements

classify elements as metals or non-metals on the basis of their properties

be aware that some elements possess

characteristics of both metals and non-metals

state and compare the relative charges and the relative masses of a proton, a neutron and an

Students should learn Students should be able to

 isotopes

 isotopic masses and relative atomic masses based on 12C=12.00

 electronic arrangement of atoms (up to Z=20)

 stability of noble gases related to their electronic arrangements

describe the structure of an atom in terms of protons, neutrons and electrons

interpret and use symbols such as 2311Na

deduce the numbers of protons, neutrons and electrons in atoms and ions with given atomic numbers and mass numbers

identify isotopes among elements with relevant information

perform calculations related to isotopic masses and relative atomic masses

understand and deduce the electronic arrangements of atoms

represent the electronic arrangements of atoms using electron diagrams

relate the stability of noble gases to the octet rule

b. The Periodic Table

 the position of the elements in the Periodic Table related to their electronic arrangements

 similarities in chemical properties among elements in Groups I, II, VII and 0

 understand that elements in the Periodic Table are arranged in order of ascending atomic number

 appreciate the Periodic Table as a systematic way to arrange elements

 define the group number and period number of an element in the Periodic Table

 relate the position of an element in the Periodic Table to its electronic structure and vice versa

 relate the electronic arrangements to the chemical properties of the Groups I, II, VII and 0 elements

 describe differences in reactivity of Groups I, II and VII elements

 predict chemical properties of unfamiliar elements in a group of the Periodic Table

Students should learn Students should be able to

c. Metallic bonding describe the simple model of metallic bond

d. Structures and properties of metals describe the general properties of metals

relate the properties of metals to their giant metallic structures

e. Ionic and covalent bond

 transfer of electrons in the formation of ionic bond

 cations and anions

 electron diagrams of simple ionic compounds

 names and formulae of ionic compounds

 ionic structure as illustrated by sodium chloride

 sharing of electrons in the formation of covalent bond

 single, double and triple bonds

 electron diagrams of simple covalent molecules

 names and formulae of covalent compounds

 formula masses and relative molecular masses

 describe, using electron diagrams, the formation of ions and ionic bonds

 draw the electron diagrams of cations and anions

 predict the ions formed by atoms of metals and non-metals by using information in the Periodic Table

 identify polyatomic ions

 name some common cations and anions according to the chemical formulae of ions

 name ionic compounds based on the component ions

 describe the colours of some common ions in aqueous solutions

 interpret chemical formulae of ionic compounds in terms of the ions present and their ratios

 construct formulae of ionic compounds based on their names or component ions

 describe the structure of an ionic crystal

 describe the formation of a covalent bond

 describe, using electron diagrams, the formation of single, double and triple bonds

 describe the formation of the dative covalent bond by means of electronic diagram using H3O+ and NH4

+ as examples

 interpret chemical formulae of covalent

compounds in terms of the elements present and the ratios of their atoms

Students should learn Students should be able to

 write the names and formulae of covalent compounds based on their component atoms

 communicate scientific ideas with appropriate use of chemical symbols and formulae

 define and distinguish the terms: formula mass and relative molecular mass

 perform calculations related to formula masses and relative molecular masses of compounds

f. Structures and properties of giant ionic substances

 describe giant ionic structures of substances such as sodium chloride and caesium chloride

 state and explain the properties of ionic compounds in terms of their structures and bonding

g. Structures and properties of simple molecular substances

 describe simple molecular structures of substances such as carbon dioxide and iodine

 recognise that van der Waals’ forces exist between molecules

 state and explain the properties of simple molecular substances in terms of their structures and bonding

h. Structures and properties of giant covalent substances

 describe giant covalent structures of substances such as diamond, graphite and quartz

 state and explain the properties of giant covalent substances in terms of their structures and bonding

i. Comparison of structures and properties of important types of substances

 compare the structures and properties of

substances with giant ionic, giant covalent, simple molecular and giant metallic structures

 deduce the properties of substances from their structures and bonding, and vice versa

 explain applications of substances according to their structures

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 and presenting information on the discoveries related to the structure of an atom.

searching for and presenting information on elements and the development of the Periodic Table.

performing calculations related to relative atomic masses, formula masses and relative molecular masses.

drawing electron diagrams to represent atoms, ions and molecules.

investigating chemical similarities of elements in the same group of the Periodic Table (e.g. reactions of group I elements with water, group II elements with dilute hydrochloric acid, and group VII elements with sodium sulphite solution).

predicting chemical properties of unfamiliar elements in a group of the Periodic Table.

writing chemical formulae for ionic and covalent compounds.

naming ionic and covalent compounds.

exploring relationship of colour and composition of some gem stones.

predicting colours of ions from a group of aqueous solutions (e.g. predicting colour of K+(aq), Cr2O72(aq) and Cl(aq) from aqueous solutions of potassium chloride and potassium dichromate).

investigating the migration of ions of aqueous solutions, e.g. copper(II) dichromate and potassium permanganate, towards oppositely charged electrodes.

building models of three-dimensional ionic crystals and covalent molecules.

using computer programs to study three-dimensional images of ionic crystals, simple molecular substances and giant covalent substances.

building models of diamond, graphite, quartz and iodine.

predicting the structures of substances from their properties, and vice versa.

justifying some particular applications of substances in terms of their structures.

reading articles or writing essays on the applications of materials such as graphite and aluminium in relation to their structures.

Values and Attitudes

Students are expected to develop, in particular, the following values and attitudes:

to appreciate that scientific evidence is the foundation for generalisations and explanations about matter.

to appreciate the usefulness of models and theories in helping to explain the structures and behaviours of matter.

to appreciate the perseverance of scientists in developing the Periodic Table and hence to envisage that scientific knowledge changes and accumulates over time.

to appreciate the restrictive nature of evidence when interpreting observed phenomena.

to appreciate the usefulness of the concepts of bonding and structures in understanding phenomena in the macroscopic world, such as the physical properties of substances.

STSE Connections

Students are encouraged to appreciate and comprehend issues which reflect the interconnections of science, technology, society and the environment. Related examples are:

Using the universal conventions of chemical symbols and formulae facilitates communication among people in different parts of the world.

Common names of substances can be related to their systematic names (e.g. table salt and sodium chloride; baking soda and sodium hydrogencarbonate).

Some specialised new materials have been created on the basis of the findings of research on the structure, chemical bonding, and other properties of matters (e.g.

bullet-proof fabric, superconductors and superglue).

III Metals

Overview

Metals have a wide range of uses in daily life. Therefore, the extraction of metals from their ores has been an important activity of human beings since prehistoric times. This topic provides opportunities for students to develop an understanding of how metals are extracted from their ores and how they react with other substances. Students are expected to establish a reactivity series of metals based on experimental evidence.

The corrosion of metals poses a socioeconomic problem to human beings. It is therefore necessary to develop methods to preserve the limited reserve of metals. An investigation of factors leading to corrosion and of methods to prevent metals from corroding is a valuable problem-solving exercise and can help students develop a positive attitude towards the use of resources on our planet.

A chemical equation is a concise and universally adopted way to represent a chemical reaction. Students should be able to transcribe word equations into chemical equations and appreciate that a chemical equation shows a quantitative relationship between reactants and products in a reaction. Students should also be able to perform calculations involving the mole and chemical equations. The mole concepts acquired from this topic prepare students for performing further calculations in other topics of the curriculum.

Students should learn Students should be able to a. Occurrence and extraction of

metals

 occurrence of metals in nature in free state and in combined forms

 obtaining metals by heating metal oxides or by heating metal oxides with carbon

 extraction of metals by electrolysis

state the sources of metals and their occurrence in nature

explain why extraction of metals is needed

understand that the extraction of metals involves reduction of their ores

describe and explain the major methods of extraction of metals from their ores

Students should learn Students should be able to

 relation of the discovery of metals with the ease of extraction of metals and the availability of raw materials

 limited reserves of metals and their conservations

relate the ease of obtaining metals from their ores to the reactivity of the metals

deduce the order of discovery of some metals from their relative ease of extraction

write word equations for the extraction of metals

describe metal ores as a finite resource and hence the need to recycle metals

evaluate the recycling of metals from social, economic and environmental perspectives

b. Reactivity of metals

 reactions of some common metals (sodium, calcium, magnesium, zinc, iron, lead, copper, etc.) with oxygen/air, water, dilute

hydrochloric acid and dilute sulphuric acid

 metal reactivity series and the tendency of metals to form positive ions

 displacement reactions and their interpretations based on the reactivity series

 prediction of the occurrence of reactions involving metals using the reactivity series

 relation between the extraction method of a metal and its position in the metal reactivity series

describe and compare the reactions of some common metals with oxygen/air, water and dilute acids

write the word equations for the reactions of metals with oxygen/air, water and dilute acids

construct a metal reactivity series with reference to their reactions, if any, with oxygen/air, water and dilute acids

write balanced chemical equations to describe various reactions

use the state symbols (s), (l), (g) and (aq) to write chemical equations

relate the reactivity of metals to the tendency of metals to form positive ions

describe and explain the displacement reactions involving various metals and metal compounds in aqueous solutions

deduce the order of reactivity of metals from given information

write balanced ionic equations

predict the feasibility of metal reactions based on the metal reactivity series

relate the extraction method of a metal to its position in the metal reactivity series

Students should learn Students should be able to c. Reacting masses

 quantitative relationship of the reactants and the products in a reaction as revealed by a chemical equation

 the mole, Avogadro’s constant and molar mass

 percentage by mass of an element in a compound

 empirical formulae and molecular formulae derived from

experimental data

 reacting masses from chemical equations

understand and use the quantitative information provided by a balanced chemical equation

perform calculations related to moles, Avogadro’s constant and molar masses

calculate the percentage by mass of an element in a compound using appropriate information

determine empirical formulae and molecular formulae from compositions by mass and molar masses

calculate masses of reactants and products in a reaction from the relevant equation and state the interrelationship between them

solve problems involving limiting reagents

d. Corrosion of metals and their protection

 factors that influence the rusting of iron

 methods used to prevent rusting of iron

 socioeconomic implications of rusting of iron

 corrosion resistance of aluminium

 anodisation as a method to enhance corrosion resistance of aluminium

describe the nature of iron rust

describe the essential conditions for the rusting of iron

describe and explain factors that influence the speed of rusting of iron

describe the observations when a rust indicator (a mixture of potassium hexacyanoferrate(III) and phenolphthalein) is used in an experiment that investigates rusting of iron

describe and explain the methods of rusting prevention as exemplified by

i. coating with paint, oil or plastic ii. galvanising

iii. tin-plating iv. electroplating v. cathodic protection vi. sacrificial protection vii. alloying