Lesson Notes By Weeks and Term - Senior Secondary School 1

SUBJECT: CHEMISTRY

CLASS:� SS 1

DATE:

TERM: 1st TERM

REFERENCE MATERIALS

• New School Chemistry for Senior Secondary School by Osei Yaw A.
• Practical Chemistry for Schools and Colleges by G. O. Ojokuku
• Calculation in Chemistry by E.U. Akusoba and G.O Ewelukwa
• WASSCE Past Questions and Answers on Chemistry
• UTME Past Questions and Answers on Chemistry

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WEEK FIVE

TOPIC: COMPOUNDS AND MIXTURES

CONTENT

• COMPOUND
• FORMULAE OF COMPOUNDS
• MIXTURES
• DIFFERENCES BETWEEN COMPOUNDS AND MIXTURES

COMPOUND

A Compound is a substance which contains two or more elements chemically combined together. A compound is formed as a result of chemical change.

Examples of compounds are

Compound��� ��� ��� Constituent Elements

Water��� ��� ��� ��� Hydrogen, oxygen

Sand��� ��� ��� ��� silicon, oxygen

Limestone��� ��� ��� calcium, carbon, oxygen

Common salt��� ��� ��� sodium, chlorine

Ethanol��� ��� ��� carbon, hydrogen, oxygen

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PROPERTIES OF A COMPOUND

1. It has properties different from those of its component elements.
2. Its formation often requires large amount of heat.
3. It cannot be separated by physical means.
4. The components of a compound have a fixed ratio by mass.
5. Compounds are homogenous.

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EVALUATION�

1. Define a compound.
2. Give three examples of a compound.

FORMULAE OF COMPOUNDS

When an element exists as a molecule, a number is written as a subscript after the symbol of that element. For example, hydrogen is written as H2 and oxygen as 02.�

A compound contains whole numbers of atoms of the component elements. Its molecular formula is written as follows.

1. The symbols of all the component elements are written close together as a group.
2. The number of atoms of each component element is written as a subscript after the symbol of that element.

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Examples

��� Compound��� ��� ��� Formula

��� Hydrochloric acid��� ��� HCl

��� Water��� ��� ��� ��� H20

��� Ammonia��� ��� ��� NH3

��� Carbon(IV)oxide��� ��� C02

��� Lead II chloride��� ��� PbCl2

��� Calcium trioxonitrate(V)��� Ca(NO3)2

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WRITING FORMULA FROM VALENCIES

Formulae of compounds can be deduced from the valencies of the component elements or radicals, following the rules below.

1. Write the symbols of the element or radicals in a compound
2. Write their valencies below the symbols of elements/radicals
3. Exchange their valencies.
4. Now write the formula of the compound bringing the symbols of the element or radicals together

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Examples

1. Write the formula of sodium tetraoxosulphate(VI)

Rule 1��� ��� ��� Na��� ��� ��� S04

Rule 2 & 3��� ��� 1��� ��� ��� 2

Rule 4��� ��� ��� Na2S04

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1. Write the formula of calcium chloride

Rule 1��� ��� ��� Ca��� ��� ��� Cl

Rule 2 & 3��� ��� 2��� ��� ��� 1

Rule 4��� ��� � � � � � � CaCl2

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EVALUATION

1. Write the formulae of; (i) tetraoxosulphate(vi) acid (ii) Magnesium Chloride
2. State three properties of a compound

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MIXTURES

A mixture contains two or more constituents which can easily be separated by physical methods.

Examples of mixtures with their constituents are outlined below:

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Mixture��� ��� ��� ��� ��� � � � � � � Constituents

Air��� Oxygen, Carbon (iv)oxide, nitrogen, rare gases, dust, moisture

Soil��� Sand, clay, humus, water, air, mineral salts

Urine��� urea, water, mineral salt

Palm wine��� water, sugar, alkanol, mineral salts, vitamins, yeast, protein, fat

Coca-cola��� water, sugar, cola, CO2�

Milk ��� water, sugar, fat, protein, mineral salts, vitamin

Sea water��� water, mineral salts, bacteria, remains of organic matter

Brass��� copper and zinc

DIFFERENCES BETWEEN MIXTURES AND COMPOUNDS

������Mixture��� Compound

1. It may be homogenous It is always homogenous.

��� or heterogeneous.

2. It can be separated into It cannot be separated into its�

��� its constituents by physical��� components by physical means.�

��� means�

3. The constituents can be The components are present in a�

��� added in any ratio by mass��� fixed ratio by mass. Hence a�

��� Hence a mixture cannot be��� compound can always be repre-

��� represented by a chemical��� sented by a chemical formula.

��� Formula.

4. The properties of a mixture The properties of a compound

��� are the sum of those of its��� are entirely different from those

��� individual constituents.��� of its components.

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EVALUATION

1. List five (5) compounds and their formulae
2. What is a mixture?
3. State four differences between compound and mixture

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READING ASSIGNMENT

• New School Chemistry for SSS by O.Y Ababio. Pg 11, 36 to 37

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GENERAL EVALUATION/REVISION

1. State the valency of the following elements and radicals: Na, K, S, O, SO42-, NO3-, CO32-�
2. Write the formula of: a) Lead (ii) tetraoxosulphate (vi) b) Hydrochloric acid c) Sodium trioxocarbonate (iv) d) Calcium hydroxide

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WEEKEND ASSIGNMENT���

1. Which of the following is a mixture? (a) water(b) sugar(c) milk (d) starch
2. Which of the following is a compound?� (a) water (b) soil (c) diamond (d) graphite
3. Which of these formulae represents ammonia? (a) NH3 (b) NH4+ (c) NH2 (d) CH4
4. The formula for sand is (a) C02 (b) SO2 (c) NO2 (d) SiO2
5. Compounds are always (a) heterogeneous (b) homogeneous (c) homogeneous or heterogeneous (d) chemogeneous

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THEORY

1. a. Define (i) Compound (ii) Mixture
2. Give two examples each of compound and Mixtures
3. a. State four differences between compound and mixture
4. What is the formula of
5. i) tetraoxosulphate (vi) acid
6. ii) Ammonium sulphide

��� iii) Sodium tetraoxophosphate�