INTRODUCTION TO CHEMISTRY

 Table of Contents
What is Chemistry?
 Matter
 Properties of matter
 Mixtures
 Conductors and non conductors
 Drugs and drug abuse
 Role of Chemistry in society
 Apparatus used in Chemistry
 Sources of heat
 The Bunsen burner
 Safety in the laboratory
 Revision

Objectives
By the end of this chapter, the learner should be able to:
• Define Chemistry.
• Identify the topics studied in Primary School Science which are part of Chemistry.
• State the role of Chemistry in society and identify some applications of Chemistry in
everyday life.
• Identify and state the use of common apparatus in the laboratory.
• Operate a Bunsen Burner.
• Observe safety in the laboratory.

Content
1. Review the following topics:
• properties of matter
• states of matter
• mixtures and their separations - conductors and non-conductors of electricity
• Mention of drugs (prescription, dosage and abuse)
2. Chemistry and the Society
• Definition of chemistry and its role in the society
3. Chemistry laboratory
• heating apparatus
• parts of a Bunsen burner and its flame
• measuring apparatus (volume, temperature, mass, time)
• other apparatus
• laboratory safety rules.
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
(v) Biochemistry.

Review of Chemistry topics learned in the Primary

Science course
 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.
NB: 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.

 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.

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 Introduction to Chemistry 3
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.

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 emphasises 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.
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.

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 Introduction to Chemistry 5
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 there in.
(ii) Glass and plastic also do not react with most of the reagents used in the
laboratory.

(a) 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.
  To measure approximate volumes, graduated beakers, flasks and measuring
cylinders are used.
 When fairly accurate volumes are required, volumetric flasks, syringes, pipettes
and burettes are used.

(b) Apparatus for general uses

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Introduction to Chemistry 7
 (c) Apparatus for measuring temperature
 Temperature is measured using thermometers. There are different types of
thermometers such as maximum and minimum, clinical and general purpose
thermometers such as the one shown below which is commonly used in the
laboratory.

(d) 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.

(e) 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.

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 Introduction to Chemistry 9
(f) 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:
(i) measuring accurate volumes of liquids
(ii) measuring approximate volumes of liquids
(iii) 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.

Parts of a Bunsen burner.

(a) 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.

(b)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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 Introduction to Chemistry 11
 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.
(c) 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 30cm of water in an identical beaker and heat it with a
3

non-luminous flame of the same Bunsen burner.

 In each case, observe the part of the beaker that was in contact with the flame.

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 manila 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.

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 Introduction to Chemistry 13

Questions
1. Draw diagrams to show how the pieces of paper and the splints were affected
when placed in:
(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.

Review Exercise 3
1. The following diagram represents a non-luminous flame of the Bunsen burner.
 (a) Name the parts of the flame labelled A, B and C.
(b) Which of the parts in (a) above is the hottest?
(c) A non-luminous flame is preferred for heating. Explain.
(d) (i) Name the other type of flame produced by a Bunsen burner.
(ii) Under what conditions does the Bunsen burner produce the flame you have
named in d (i)?
(e) After use, a non-luminous flame should be put off or adjusted to a luminous
flame. Explain.
2. (a) What is a flame?
(b) Which type of flame is produced when the air hole of a Bunsen burner is closed?
(c) Draw a well labeled diagram of the type of flame in (b) above.
(d)State four observable differences between a luminous and a non-luminous flame.

3. A piece of paper was slipped in and out of the regions (i) and (ii) of the non-luminous
flame as shown below.

(a) Draw diagrams to show how the pieces of paper were affected when placed in:
(i) region (i).
(ii) region (ii) of the flame.
(b) Explain the observations made.
(c) What would be observed if wooden splints were used instead of the paper?
(c) From the experiments above, which part of the flame is preferred for heating? Why?.

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 Introduction to Chemistry 15

Revision exercise
1. (a) What is chemistry?
(b) Is chemistry important to the society? Explain.
(c) Name three careers where knowledge of chemistry is required.
2. (a) What is a drug?
(b) Define the following terms
i) Drug abuse
ii) Prescription
iii) Dose
(c) Give four drugs that are commonly abused by the youth.
(d ) give any 5 harmful effects of drug abuse
(e)Why is it very necessary to follow the doctor’s prescription when taking medication?
3. Give the names of the apparatus used for
(i) measuring accurate volumes of substances
(ii) measuring approximate volumes of substances.
(iii) measuring mass.
4. Why are most of the apparatus in chemistry laboratories made of glass?
5. Which other apparatus can be used for heating purposes in the laboratory apart
from the Bunsen burner?
6. Name the three states of matter.
7. (a) The diagram below shows apparatus commonly used in a school laboratory.

(i) What is the name of apparatus?

(ii) Label the following parts: region of unburnt gas, chimney, jet, collar.
(b) What do you call the flame produced when the air hole is open?
(c) Explain briefly why the luminous flame, produces light while the non-luminous flame
does not.

8. Name the regions labelled a, b and c in the diagram below. Which region is
used for heating? Give a reason.

(a)

(b)

(c)
9. Wooden splints F and G were placed in different zones of a Bunsen burner flame.
The diagram below gives the observations that were made
Burnt parts
Burnt part

(a) Explain theG difference between F and G F

(b) Name the type of flame that was used in the above experiment

10. State two reasons why we use the non-luminous flame in the laboratory
instead of the luminous flame.
11. State six differences between a luminous and non-luminous flam
12. (a). The diagrams below represent a list of apparatus which are commonly used in a
chemistry laboratory:-

A B C D E

Give the names and uses of all the apparatus.

(b) State any 5 laboratory rules.
(c) What do you call the method of obtaining clean water from muddy water?
(d) Name a non-metal which conducts electricity.
13. (a) When the air-hole is fully opened, the bunsen burner produces a non-luminous
flame.Explain
(b) Draw a labelled diagram of anon-luminous flame
14. (a) What is a drug?
(b) Give two drugs that are commonly abused by the youth.
15. The diagrams below are some common laboratory apparatus. Name each apparatus
and state its use

Diagram Name Use

(½mk ) (½mk)

(½mk) (½mk)

16. The diagram below shows some parts of a Bunsen burner

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 Introduction to Chemistry 17

T
U

Explain how the parts labelled T and U are suited to their functions

17. The diagram below shows the appearance of two pieces of paper placed in different
parts of a non-luminous flame of a Bunsen burner and removed quickly
before they caught fire.

(a) What do the experiments show about the outer region of the flame?
(b) From the above experiment, which part of the flame is better to use for heating?
Give a reason