INTRODUCTION TO CHEMISTRY

Table of Contents
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Table of Contents................................................................................................................. - 1 -
Objectives............................................................................................................................. - 1 -
Content................................................................................................................................. - 1 -
What is Chemistry?............................................................................................................... - 2 -
Review of Chemistry topics learned in the
Primary Science course................................................................................................... - 2 -
Matter............................................................................................................ - 2 -
Properties of matter........................................................................................- 2 -
Mixtures......................................................................................................... - 3 -
Conductors and non-conductors.......................................................................- 3 -
Drugs and drug abuse.....................................................................................- 3 -
Role of chemistry in the society............................................................................................- 3 -
The Chemistry Laboratory.................................................................................................... - 4 -
Safety in the laboratory...................................................................................- 4 -
Apparatus used in Chemistry................................................................................................ - 5 -
The Bunsen Burner..........................................................................................- 9 -

Objectives

By the end of this chapter, the

learner should be able to:
(a) Define Chemistry.
(b) Identify the topics studied in Primary
School Science which are part of
Chemistry.
(c) State the role of Chemistry in society
and identify some applications of
Chemistry in everyday life.
(d) Identify and state the use of common
apparatus in the laboratory.
(e) Operate a Bunsen Burner.
(f) Observe safety in the laboratory.
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INTRODUCTION TO CHEMISTRY ⚗
Chemistry is one of the three Science subjects. The other two subjects are Biology and
Physics.

What is Chemistry?
Chemistry is the study of the structure, properties and composition of
matter and the changes that matter undergoes.
States of matter and its properties, mixtures and their methods of separation and
drugs are studied under Chemistry.
The study of Chemistry involves carrying out experiments, making observations,
analysis, interpretation and making conclusions.
There are many branches of chemistry. The five main branches are considered to be:
(i) Organic Chemistry,
(ii) Inorganic Chemistry,
(iii) Analytical Chemistry,
(iv) Physical Chemistry, and
(v) Biochemistry.

Review of Chemistry topics learned in Primary

Science
Topics covered in primary science, which are studied under Chemistry include:
Properties of matter, mixtures and methods of separation, drugs and pollution.
Matter
Matter is anything that has mass and occupies space. Matter exists in three
states namely solid, liquid and gas (vapour).
The three states of matter are interconvertible.

Properties of matter

Physical properties of solids

Solids have definite shapes that are not easily changed. Solids also have a definite
mass and volume.
Mass is a measure of the amount of matter in a substance. Volume is the space
occupied by a substance.

Different sizes of the same substance contain different amounts of matter and
therefore have different masses. When a solid is put in water, the water level rises.
The rise in water level represents the volume of the solid.

Physical properties of liquids.

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Liquids have a definite mass and volume but take the shape of the containers
in which they are placed due to their ability to flow.

Physical properties of gases.

Gases have a definite mass but do not have definite volume or shape. They can
therefore be compressed to occupy small spaces and also expanded.

Mixtures
Matter is found either as pure substances or mixtures. A pure substance is one that
consists of only one type of matter.
A mixture consists of two or more substances mixed together and in which the
individual components forming the mixture retain their physical and chemical
properties.
A mixture can be separated by physical means such as winnowing, sieving, filtering,
evaporating, decanting and use of magnets. The choice of method to separate a given
mixture depends on the nature and properties of the individual components forming
the mixture.
Conductors and non-conductors
Substances which allow electrical energy to flow through them are conductors.
Substances which do not allow electricity to flow through them are non-conductors.
Drugs and drug abuse
A drug is any substance, natural or manufactured which when used alters
the way the body functions.
Drugs used to treat diseases in human beings and other animals are known as
medicines.
Medicines are administered by qualified medical officers in specific amounts called
doses.
The written instructions by a qualified medical officer, giving details on the type of
drugs and how the drugs should be used is called a prescription.
The use of a drug for a purpose other than what it is meant for, or use of
overdose or underdose of prescribed drugs constitutes drug abuse.
Drug abuse has harmful effects on the state of health of the user. The harmful
effects include stress, depression, hallucination, addiction and dependency or
may be fatal.
The commonly abused drugs are tobacco, alcohol, bhang and khat (miraa).
Harmful effects of smoking tobacco include lung cancer and heart failure.
Alcohol abuse leads to liver problems (liver cirrhosis).
Misuse of bhang leads to mental disorders.
Prolonged use of khat leads to addiction, dependency and vascular disorders.
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Role of chemistry in the society

In Chemistry, substances are referred to as chemicals. The people who work with
chemicals are Chemists.
Chemistry offers various career opportunities in various fields such as medicine,
pharmacy, food technology, education and engineering.
Chemistry has helped to improve standards of living in areas such as:
1. Manufacture of drugs to fight diseases.
2. Food production to fight hunger.
3. Manufacture of cheaper alternative fabrics such as nylon, polyester and tetron.
4. Manufacture of plastics for roofing, packaging and domestic use.
5. Manufacture of detergents.
6. Production of fuels for transport and domestic use. This includes alternative fuels
to reduce global pollution as well as to supplement the fossil fuels.

Review Exercise 1.

1. (a) Define chemistry.

(b) What role does chemistry play in the society?
2. (a) What is a drug?
(b) Name three frequently abused drugs
(c) State two long-term effects of drug abuse
(d) Differentiate between a dose and a prescription.
3. (b) Name four career opportunities open to a Chemist.

The Chemistry Laboratory

A laboratory is a building or special room where chemicals and apparatus are
kept and in which practical subjects such as Chemistry are studied.
Safety in the laboratory
Since learning chemistry emphasizes on practical work, it is necessary that certain
rules are followed to ensure safety in the Chemistry laboratory.
The two common causes of accidents in the laboratory are ignorance and
carelessness. Accidents are minimised when safety rules are followed.
All chemicals with environmental and health impacts must be stored in well labelled
containers with appropriate safety warning symbols clearly visible.
Laboratory safety rules
1. NEVER run while in the laboratory because you may trip, fall and injure yourself or
other users of the laboratory.
2. NEVER taste or eat anything in the laboratory to avoid poisoning.
3. Always consult your teacher before trying any experiment to avoid accidents.
4. Label all the chemicals you are using to avoid confusion.
5. Always use a clean spatula for scooping a substance from a container to prevent
contamination.
6. Always hold test-tubes or boiling tubes using a test-tube holder when heating to
avoid being burned.
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7. When heating a substance in a test tube or boiling tube, NEVER let the open end
face you or anybody else because the liquid may spurt out and cause injury.
8. NEVER look directly into flasks and test-tubes where reactions are taking place,
because the chemicals may spurt into your eyes and cause injury.
9. NEVER smell gases directly, instead waft the gas towards your nose with your
hand.
10. Experiments in which poisonous gases are produced must be carried out in a fume
cupboard or outdoors.
11. Always keep flammable substances away from flames because they easily catch
fire.
12. Report any accidents to the teacher or the laboratory technician immediately for
necessary action.
13. In case of a serious accident such as fire, calmly walk out, DONT SCRAMBLE for
the exit. Doing so would hinder easy escape.
14. Always extinguish flames that are not in use to avoid accidents and minimise fuel
wastage.
15. If a chemical gets on your skin or in your mouth rinse it immediately with a lot of
clean water.
16. Chemicals already used must always be disposed off safely to avoid
contamination.
17. Always work on a clean bench. Clean all the pieces of apparatus used and store
them at the end of each experiment.

Apparatus used in Chemistry

Most laboratory apparatus which are used as containers and reaction vessels are
made of transparent glass or plastic.

The reasons why most apparatus in the laboratory are made of glass and
plastic is:
(i) To allow one to see through while observing the reactions taking place or to
determine the level of the liquids held therein.
(ii) Glass and plastic also do not react with most of the reagents used in the
laboratory.

Ceramic materials are normally used for heating because they don’t crack
easily when heated.

Apparatus for measuring volume

All apparatus used for measuring volumes of liquids are usually of transparent glass
or plastic. The apparatus used for measuring volumes of liquids include a graduated
beaker and flask, a measuring cylinder, volumetric flask, syringe, pipette and burette.
Apparatus for measuring exact/accurate volume
When fairly accurate volumes are required, volumetric flasks, syringes, pipettes
and burettes are used.
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Apparatus for measuring approximate volume.

To measure approximate volumes, graduated beakers, flasks and measuring
cylinders are used.

Apparatus for holding substances

Apparatus Name Use
Pair of tongs/tongs Safely holding corrosive or
hot solids.

Test-tube holder Holding test-tubes when

they are being heated

Clamp and stand Holding and supporting

pieces of apparatus during
experiments

Deflagrating spoon For holding substances

when being burned.

Test-tube rack For holding test-tubes and

boiling tubes.
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Mortar and pestle For crushing substances

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Apparatus for measuring temperature

Temperature is measured using thermometers. There are different types of
thermometers such as maximum and minimum, clinical and general-purpose
 Introduction to Chemistry|9

thermometers such as the one shown below which is commonly used in the
laboratory.

Apparatus for measuring mass

Mass is measured using weighing balances. There are different types of weighing
balances such as beam balances, electronic balances and top pan balances.
Apparatus for measuring time
The apparatus for measuring time are watches and clocks. For accuracy during
experiments in the laboratory, stop watches and stop clocks are used.

Sources of Heat
The pieces of apparatus used as sources of heat include the Bunsen burner, spirit
lamp, candle, gas stove (portable burner), kerosene stove and electric heater. The
Bunsen burner is the most suitable source of heat in laboratories.

Review Exercise 2

1. (a) What is a laboratory?

(b) Explain why most laboratory apparatus are made of glass.
2. (a) What are the two causes of accidents in the laboratory?
(b) Putting off flames after use is one of the safety rules in the laboratory. State
five other rules
3. Give two apparatus used in the chemistry laboratory for:
(a) measuring accurate volumes of liquids
(b) measuring approximate volumes of liquids
(c) measuring mass

The Bunsen Burner

A Bunsen burner consists of three major parts. These are the chimney, the collar and
the base as shown below.
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Functions of the different parts of a Bunsen burner

 The base is made of thick metallic material into which a small hollow metal
with a jet is fitted. The base is heavy and wide to keep the Bunsen burner
stable.
 The jet allows the laboratory gas into the chimney.
 The gas inlet in the Bunsen burner is normally connected to an external source
of laboratory gas by rubber tubing to let in the lab gas.
 The collar is a metal ring which may have an air hole whose diameter is the
same size as that of the hole in the chimney. The diameter of the collar is slightly
bigger than that of the chimney so that the chimney can just fit into it.
The collar is used to regulate the amount of air entering the chimney.
 The chimney is a hollow metallic cylinder with an air hole near its lower end.
The air hole in the chimney allows air to enter and mix with the laboratory gas
from the jet. This mixture of gases (laboratory gas and air), when ignited burn at
the top of the chimney to produce a flame.

Types of flames produced by a Bunsen burner

A flame is a mass of burning gases.

When in use, a Bunsen burner produces two types of flames depending on the amount
of air allowed into the chimney.
The luminous flame
A luminous flame is produced when the air hole is closed such that no air enters
the chimney of a Bunsen burner.
The luminous flame produces light because it contains unburnt tiny particles
of hot glowing solid carbon which give out light due to incomplete combustion
of the gas since there is limited supply of air.
To produce a luminous flame, connect the burner to a gas tap and close the air hole.
Turn on the gas fully and light the burner.

The luminous flame is:

(i) Bright yellow
(ii) Large and wavy.
(iii) It gives out much light (luminous)
(iv) A luminous flame has four zones.
(v) Produces soot
(vi) Burns silently
The blue zone occurs at the bottom of the
flame. Air near the flame rises rapidly and mixes with the burning gas. This makes
burning almost complete.
The almost colourless zone of the flame consists mainly of unburnt gases.
The luminous bright yellow zone consists mainly of unburnt tiny particles of hot
glowing solid carbon which give out light. The unburnt carbon particles form
the black soot which makes apparatus dirty during heating. Air supply in the bright
yellow zone is limited and there is incomplete combustion of the gas.
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In the thin outer pale blue zone, the gas burns completely because it mixes with
plenty of air. However, this region is normally difficult to see.

The non-luminous flame

The non-luminous flame is produced when the air hole of the Bunsen burner is
open. When the air hole is open, air enters the chimney and mixes with the
laboratory gas. There is complete combustion of the gas and therefore the flame
produced is pale blue in colour. It does not give out much light.
To obtain a non-luminous flame, connect the burner to a gas tap and close the air
hole. Turn on the gas fully and light the burner. Turn the collar gradually until the hole
is fully open.
The non-luminous flame:
(i) Has three zones.
(ii) Is short and steady
(iii) Does not give out much light
(iv) Burns with a roaring sound
(v) Does not produce soot.
The almost colourless zone consists of unburnt
gases.
The green blue zone contains partially burnt gases due to insufficient supply of
air.
In the outer pale blue zone, the gases burn completely because there is plenty
of air.
The non-luminous flame gives out only a little light because it contains fewer
hot carbon particles.

Heating effects of the luminous and non-luminous flames.

Light a Bunsen burner and adjust the collar to produce a luminous flame. Pour 30cm 3
of water into 100ml glass beaker. Heat the water in the beaker and note the time it

takes to boil.

Repeat the experiment using 30cm3 of water in an identical beaker and heat it with a
non-luminous flame of the same Bunsen burner. In each case, observe the part of the
beaker that was in contact with the flame.
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Questions
1. Which water sample took a shorter time to boil?
Water heated by a non-luminous flame took a shorter time to boil than the same
amount of water heated by a luminous flame. This shows that the non-luminous
flame is hotter than the luminous flame.
2. What was observed at the bottom of each beaker?
The bottom of the beaker heated using the luminous flame is covered with
soot while the beaker heated using a non-luminous flame remains clean.
3. Explain the observations you have made.
The Water heated by a non-luminous flame took a shorter time to boil than the
same amount of water heated by a luminous flame because the non-luminous
flame is hotter than the luminous flame due to complete combustion.
The luminous flame produces soot due to the presence of unburnt carbon
particles. .
4. Which type if flame is preferred for heating and why?
The non-luminous flame. Because:
(i) The non-luminous flame is very hot compared to the luminous flame
(ii) The non-luminous flame does not produce soot.
5. Which flame is preferred for lighting and why?
Luminous flames such as the candle flame and flame of lantern lamps are
normally used for lighting because they give out light.

Which is the hottest part of a non-luminous flame?

Light a Bunsen burner and adjust the collar to obtain a non-luminous flame. Slip a
piece of white manilla paper into the flame in region (i) as shown below.
Quickly remove the paper before it catches fire. Slip a fresh piece of white manilla
paper into region (ii) of the flame as shown in figure 1.0 (b). Quickly remove it before
it catches fire.

Now repeat the experiments using wooden splints instead of white manilla paper. Let
each splint stay in the flame until some of its parts get charred. Record your
observations.
Questions
1. Draw diagrams to show how the pieces of paper and the splints were
affected when placed in:
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(a)region (i).

When a piece of paper is quickly slipped in and out of region (i) of the non-luminous
flame, the paper is partly burnt in the regions that are in contact with the pale blue
zone. The middle part of the paper remains unburnt (no charring).

(b)region (ii) of the flame.

When a piece of paper is slipped in and out of region (ii) of the non-luminous
flame, it burns uniformly.

2. Draw diagrams to show how the wooden splints were affected when
placed in both regions.
When wooden splints are used instead of paper, similar results
3. What conclusions can be made from these experiments?
These experiments show that the outer most zone in a non-luminous flame is
hotter than the inner zones.

4. Which part of the flame is suitable for heating substances?

The outermost region of the flame. This is the hottest region of the flame
because of complete combustion.