SMSA YEAR 8 SCIENCE NOTES AND QUESTION BOOKLET

THE DIGESTIVE SYSTEM

All mammals have similar digestive systems.
The digestive system has two parts:
PART 1:
The alimentary canal – consists of the mouth, oesophagus,
stomach, small intestine and large intestine (includes the
rectum and anus);
PART 2:
The associated organs consist of the liver and pancreas.

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Food travels through our body along the alimentary canal which begins at the mouth and ends at the anus.
Mouth

Anus

ORGAN ROLE OF DIGESTIVE ENZYMES
MOUTH Digestion starts in the mouth.
Chewing action by the teeth
(mastication) breaks down large
pieces of food into smaller
pieces.
Chewing also makes the food
softer and easier to swallow.

The tongue helps to mix the food
with saliva.
The saliva contains carbohydrase
that helps to digest starch into
simple sugar.
The tongue rolls the food into a
ball.

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STOMACH The ball of food is then moved
SMALL INTESTINE down to the stomach through
the oesophagus.
The stomach is a muscular organ
that secretes gastric juices,
which contain an acid and
proteases.
The acid helps the proteases in
the digestion of protein.
It also kills microorganisms.
The stomach mixes the food with
the gastric juice through a
churning action.

Small intestine is about 6 to 7
metres long.

Contains the enzymes
carbohydrase, protease and
lipase.

These complete the digestion of
the food into its simplest forms
(simple sugars, amino acids, fatty
acids and glycerol).

These are then absorbed into the
bloodstream.

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Large intestine is about 1.5

metres long.

Undigested food

Fibre pass into
Water the large
Minerals intestine

Vitamins.

LARGE INTESTINE Water

Minerals are absorbed

Vitamins

The rest of the undigested food

(waste materials) is temporarily

stored in the rectum before

being removed as faeces through

the anus.

HOW DOES FOOD MOVE?

• The muscles in the wall contract and relax, producing a wavelike pattern called peristalsis, which
pushes the food down.

• Peristalsis allows the food to be mixed with the digestive juices, while pushing the food along the
alimentary canal.

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55Page

ABSORPTION OF FOOD

Digested food consists of many simple and soluble particles, which move through the walls of the small
intestine into the blood.

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CHAPTER 12: PLANT AND ANIMAL NUTRITION

TOPIC 12.1: PHOTOSYNTHESIS

1. A small plant was placed into a conical flask containing water and set up as shown in figure below. After
8 hours in sunlight, the water level in the test tube was seen to have fallen slightly. What is the possible
reason for this fall in water level?
(SPE/2011/Q27)

A. Water is reduced from the conical flask by evaporation.
B. Water is taken up by the plant for photosynthesis.
C. Water is reduced from the conical flask by diffusion.
D. Water is absorbed by the oil.

2. Photosynthesis in plants plays an important role in an ecosystem (environment). Which of the following
is NOT an important result of photosynthesis?
(SPE/2012/Q16)

A. It increases the amount of oxygen in the air.
B. It increases the amount of water vapour in the air.
C. It produces food for living things.
D. It removes carbon dioxide from the air.

3. Figure below shows the photosynthesis process. Which gas represents gas 1 and gas 2 above?
(SPE/2014/Q30)

Gas 1 Gas 2
A. Carbon dioxide Carbon monoxide

B. Carbon dioxide Oxygen
C. Oxygen Carbon dioxide
D. Oxygen Carbon monoxide

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4. Which of the following are the correct conditions and raw materials for photosynthesis?

(SPE/2010/Q24)

Conditions Raw materials

A. Chlorophyll and light Carbon dioxide and water
B. Carbon dioxide and water Chlorophyll and light
C. Oxygen and water Carbon dioxide and chlorophyll
D. Air and room temperature Carbon dioxide and oxygen

5. An experiment was carried out as shown I the diagram. The gas collected in the test tube will…..
(SPE/2009/Q17)

A. relight a glowing splint.
B. turn limewater milky.
C. produce a ‘pop’ sound with a burning splint.
D. turn dry cobalt chloride paper from blue to pink.

6. Khalid carried out an experiment to test the presence of starch in a tomato leaf. Steps involved in the
experiment are shown in figure below.

The correct sequence of steps should be…..
(SPE/2015/Q32)

A. l  ll  lV  lll C. lV  l  ll  lll
B. ll  lV  l  lll D. lV  ll  l  lll

7. With the aid of the labelled diagrams in figure below. Complete the following passage by using the
helping words provided.

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ethanol iodine blue-black kerosene fats
protein starch sugar photosynthesis chlorophyll

A green leaf is placed in boiling water for 30 seconds in order to kill the leaf cells. The leaf is then
transferred into a test tube of _____________________. The test tube is left in hot water for about five
minutes. The colour of ethanol turns green. The ____________________ in the leaf is absorbed by the
ethanol. The leaf is then put back into a beaker of hot water to remove the ethanol and soften the leaf.
After that, the leaf is placed on a white tile and few drops of ___________________ is added. The leaf
turns ___________________ in colour. This shows that _____________________ is present in the leaf.

TOPIC 12.2: FOOD AND ITS IMPORTANCE

1. A group of Year 8 students carried out two tests on a food sample. Table below shows the results of the

tests. (SPE/2013/Q27)

Test Results
1. Benedict’s solution is added to the food sample Orange precipitate

and the mixture is heated.

2. Biuret solution is added to the food sample. Blue solution remains
Shake the mixture.

What can you conclude from the results?
A. Both protein and sugar present.
B. Both protein and sugar is absent.
C. Protein is present but not sugar.
D. Sugar is present but not protein.

2. Solution X produces a red precipitate when heated with Benedict’s solution. A purple colour develops
when the Biuret test is used on Solution X. Which nutrients are present in Solution X?
(SPE/2010/Q21)

A. Fat and protein.
B. Fat and starch.
C. Reducing sugar and protein.
D. Reducing sugar and starch.

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3. Azam carried out an experiment to detect the presence of protein in food sample A and B using Biuret
test. Figure below shows how he prepares the food samples for testing.

Which sets up should he use to ensure a fair test? Food sample B
(SPE/2016/Q28)

Food sample A

A. 2 cm3 of distilled water + 2 drops of 2 cm3 of distilled water + 5 drops of
Biuret solution Biuret solution

B. 2 cm3 of distilled water + 5 drops of 4 cm3 of distilled water + 5 drops of
Biuret solution Biuret solution

C. 4 cm3 of distilled water + 5 drops of 4 cm3 of distilled water + 2 drops of
Biuret solution Biuret solution

D. 2 cm3 of distilled water + 5 drops of 2 cm3 of distilled water + 5 drops of
Biuret solution Biuret solution

4. Table below shows a list of vitamins and their respective deficiency diseases. (SPE/2012/Q18)

Vitamin Vitamin deficiency disease
A W
C X
D Y

Which of the following correctly represent W, X and Y?

W X Y Page60
Scurvy Night blindness
A. Beri beri Night blindness
B. Beri beri Scurvy Rickets
C. Night blindness Beri beri Rickets
D. Scurvy Rickets

5. Which group of food contains the highest amount of dietary fibre?
(SPE/2010/Q20)
A. Meat, eggs, fish and milk.
B. Sugar, rice, butter and meat.
C. Sugar, oil, butter and margarine.
D. Vegetables, fruits, rice and cereals.

6. Which group of food below can reduce the chances of getting constipation? (SPE/2013/Q26)
A. Cereals, vegetables and fruits.
B. Meat, fish, eggs and milk.
C. Rice, sugar, butter and meat.
D. Sugar, oil, margarine and butter.

7. Figure below shows experiments to test for the presence of starch and glucose. Complete the table
below by naming reagents P and Q. Record the expected observations. (SPE/2011/Q46b)

Experiment Reagent Observation

8. a) Salmah designed an experiment to investigate the presence of glucose in her meal
shown in figure below. (SPE/2014/Q45)

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She wrote down the steps taken in figure below. Page62

i) Salmah’s descriptions of her steps are not in order. Arrange her steps in correct order by adding
number 1 to 4 in the boxes in figure above.

ii) Salmah made an experimental error when adding food samples in the test tube. State the
experimental error she made.
__________________________________________________________________

iii) Write down two factors that Salmah has kept the same in this investigation.
1. _________________________________________________________________
2. _________________________________________________________________

iv) Describe a fair test that Salmah needs to do to further improve her investigation in figure above.
__________________________________________________________________

b) Salmah carried out the experiment and her results are shown In Table below.

Food samples A B C D
(Egg (Rice suspension) (Apple (Rose
Colour of the Benedict’s suspension) Juice) syrup)
solution at the start
Blue Blue Blue Blue
Colour if the Benedict’s Orange Orange
solution after 3 minutes Blue
Blue precipitate precipitate

What can Salmah conclude from her experiment?
___________________________________________________________________________

c) Salmah also carried out another investigation with the same food samples using Biuret’s
test and Iodine test. She recorded her results in Table below.

Observation

Iodine test Biuret’s test

Food samples Colour at the Colour at the Colour at the Colour at the

A (Egg suspension) start of the end of start of the end of
B (Rice suspension)
experiment experiment experiment experiment
C (Apple Juice)
D (Rose syrup) yellow yellow blue purple

yellow blue black blue blue

yellow yellow blue blue

yellow yellow blue blue

What can Salmah conclude from results in Table above?
___________________________________________________________________________

TOPIC 12.3: BALANCED DIET Page63

1. Figure below shows a food pyramid for a balanced diet. Which group of food below should be eaten in
the smallest quantity?
(SPE/2009/Q18)

A. Vegetables, fruits, rice and cereals.
B. Sugar, oil, butter and margarine.
C. Meat, eggs, fish and milk.
D. Sugar, rice, butter and meat.

2. Figure below shows different groups of food. Page64

Which group of food should be eaten more in order to reduce obesity and state the
main reason? (SPE/2011/Q25)
A. Vegetables and fruits – because they prevent constipation.
B. Butter and burger – because they tasted good.
C. Vegetables and fruits – because they contain more fibre.
D. Butter and burger – because they are high in calories.
3. Figure below shows two types of diet X and Y in the form of pie charts.
(SPE/2009/Section B Q6a)

Compare Diet X and Diet Y and answer the following questions:
a) Which diet is lacking in proteins?

_____________________________________________________________________
b) Which food group is present in Diet X but absent in Diet Y?

_____________________________________________________________________
c) What might happen if a person eats too much food from Diet X?

_____________________________________________________________________
_____________________________________________________________________

4. Table below shows the information about 6 different foods and its nutrients.
(SPE/2015/Q44a, b and c)

Nutrients per 100 g of each food

Food Protein Fats Carbohydrate Fibre Vitamin C
(g) (g) (g) (mg per 100 g)
Milk 3.3
Beef burger 10.6 3.8 4.7 0 2
Vegetable 18.5 0
burger 32.1 9.5 0 2.2
Chicken 26.5
Cabbage 1.7 12.7 11.7 4.5 0
Potato chip 0.6 23
4.0 0 0 0

0 2.3 54

2.2 8.6 0.5

a) Which food(s) in table above contains:
i) the most protein
_____________________________________________________________________

ii) no carbohydrates
_____________________________________________________________________

b) Not all the types of nutrients needed for a balanced diet are shown in table above. Name one
missing type of nutrient.

_____________________________________________________________________
c) State two reasons why a person who wants to have a healthy diet will choose the vegetable burger

instead of a beef burger.

1. __________________________________________________________________
2. __________________________________________________________________

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d) Study the situation in figure below. Page66

i) Which student is taking an unbalanced diet?
_____________________________________________________________________

ii) Give a reason for your answer in part i).
_____________________________________________________________________

iii) State two possible effects that would happen if the student stated in part i) continues eating an
unbalanced diet.
_____________________________________________________________________

TOPIC 12.4: FOOD ADDITIVES AND PROCESSED FOOD
1. Some food additives are harmful if consumed in large amounts. Which of the following is NOT true?

Food additives may…..(SPE/2010/Q28)
A. cause cancer.
B. cause children to be too active.
C. increase memory power.
D. increase weight.
2. Figure below shows an example of processed food. Which of the following is NOT a reason for adding
food additives to processed food?
(SPE/2012/Q19)
A. To increase the roughage content.
B. To make the food look attractive.
C. To make the food tastier.
D. To prevent the food from going bad.

3. Food additives are found in potato chips. Name one possible harmful effect of food additives on
children.
(SPE/2015/Q44d)
________________________________________________________________________

TOPIC 12.5: DIGESTION IN MAMMALS
1. Figure below shows the human digestive system. Which organs are NOT

involved in digesting food substances?(SPE/2011/Q29)
A. Organs A and B.
B. Organs B and C.
C. Organs A, B and C.
D. Organs A, C and D.

2. Figure below shows the human alimentary canal. Which organ contains an acid to kill harmful organisms
in the food that we eat? (SPE/2009/Q22)

3. Study the experiment in figure below. (SPE/2013/Q28)

Which of the following experiments should be carried out to ensure a fair test?

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4. a) Figure below shows the human digestive system. Draw line to match
the following description to the correct letter representing the organ.
(SPE/2010/Q45a)

b) Figure below represents digestion of protein molecule.

i. Name the group of enzymes that digests protein.
_____________________________________________________________________________

ii. What is the end product of protein digestion?
____________________________________________________________________________

5. The flowchart shows the sequence of the passage of food through part of the human alimentary canal.
(SPE/2012/Q43)

Mouth Oesophagus Stomach Small intestine

a) Digestion of carbohydrates begins in the mouth. What enzyme is involved?
_________________________________________________________________________________

b) Name the process whereby the food particles move through the oesophagus and intestines.
________________________________________________________________________________

c) Gastric juice produced in the stomach contains an enzyme which is used to digest a type of food. Page68
What is the type of food digested?
_______________________________________________________________________________

d) Pancreatic juice, intestinal juice and bile are releases into the small intestine. Where is bile
produced?
_____________________________________________________________________

e) i) Describe briefly how absorption of digested food takes place in the small intestine.
_____________________________________________________________________

(ii) State one feature of the small intestine that helps to increase the surface area of
absorption of food.

_____________________________________________________________________

f) What happens to the undigested food in the small intestine?
_____________________________________________________________________

6. Figure below shows a digestive system. (SPE/2016/Q45)

a) Name part B and D.
B : _____________________________________
D : _____________________________________

b) Using the letters in figure below, which part(s) of the digestive
system does the following takes place:
i) carbohydrate digestion : ___________________________________________

ii) protein digestion : ___________________________________________

iii) water absorption : ___________________________________________

c) Nurul and Razak carried out an experiment to investigate the breakdown of starch by amylase as
shown in figure below.

Table below shows the results of their experiment when tested with Benedict solution.

Test tube Observation

A Orange precipitate Page69

B No change

i) Based on the results in table above, what can be concluded from the experiment?
_____________________________________________________________________

ii) Give two variables that are kept the same in the experiment.
_____________________________________________________________________

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TOPIC 13.0: CURRENT ELECTRICITY

13.1 ELECTRIC CURRENT
Electricity is a useful form of energy because it can make electrical appliances work for man.
For example, electricity is being converted to heat energy in a rice cooker to cook rice.

Sources of electricity
1. Electrical energy comes from two sources:
o Power generators in power stations
o Electric cells
2. An electric cell supplies much less electricity than a power generator.
An electric cell can only supply a limited amount of electrical energy.

Where does our electricity come from?
In Brunei Darussalam, electricity is produced from natural gas, which is used to power turbines and
generators.

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ELECTRIC CIRCUITS
1. An electric circuits is made up of:
o A power source (e.g. electric cell).
o Other circuit components (e.g. bulb, connecting wires or a switch).

2. An electric circuit forms a path for an electric current to flow through.
3. If the bulb in an electric circuit lights up, the circuit is a complete circuit or a closed circuit.

A bulb can only light u when an electric current flows through it.
If the bulb in an electric circuit does not light up, the circuit is an incomplete circuit or an
open circuit
.

Open circuit
Close circuit

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Open circuits
When the switch is ‘off’, the circuit is open.
Current cannot flow through it
because the path from one terminal
to another is not complete.
The bulb will not light up.

Closed circuits
When the switch is ‘on’, the circuit is closed.
Current can flow through it because
the path from one terminal to
another is complete.
The bulb will light up.

Current
To make an electrical appliance work, electrical charge must flow through it.
This movement of electrical charge is called electric current (I).
An electric current is the flow of electrons.
The path that the current flows through is known as a circuit.

Current is measured with an ammeter.
The S.I. unit of current is ampere (A).

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When scientists first discovered current flow, they did not know that this was due to the movement of
particles called electrons.
They thought current flowed from the positive terminal to the negative terminal of a dry cell. This is
known as the “conventional current flow”.

Electric cell

Connecting wire

Bulb

Conventional current

When electrons were discovered, scientists realised that electrons actually flow from the negative terminal
to the positive terminal of a dry cell.

Flow of electrons

Electric cell

Connecting wire

Bulb

Electron flow Page74
4. In a circuit, the power source (e.g. an electric cell) provides the energy to push the electrons around

the circuits. Some of this energy is used to light up the bulb.

5. When a bulb does not light up in a complete circuit, it means that the energy in the power source is
used up.

6. An electric current is a flow of electrons. It flows from the negative terminal to the positive terminal
of the power source. Electrons move from one atom to the next.

Voltage
When current flows from one terminal of the dry cell to the other, energy is needed to move the electric
charge.
The amount of energy needed to push the charge can be referred to as the voltage.
The voltage across an electrical component is measured with a voltmeter.
The S.I. unit of voltage is volt (V).

13.2 SIMPLE ELECTRIC CURCUIT.
1. To show electric circuits, circuit diagrams are used.
Symbols are used to represent electric components in a circuit diagram.

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2. The table below shows the symbols of some electrical components.

Component Symbol Component Symbol
Battery
Electric cell

QuickTime™ and Baulb Bulb
Close switch
TIFF (Uncompressed) decompressor
are needed to see this picture.

Open switch

Fixed resistor Fuse

Rheostat Connecting wire
Voltmeter Ammeter

A circuit diagram

A dry cell Wire
Switch

A light bulb

Series and parallel circuits Page76

To light up a few bulbs at the same time, you can connect them in two (2) ways —

1. In series 2. In parallel.

In a series circuit, there is only one path for the current to flow through.

If one of the bulbs is taken out or damaged, the other bulb will not light up.

This is because the circuit is open, so no current can pass through the circuit.

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In a parallel circuit, there is more than one path for the current to flow through.

Some current passes through one bulb and the rest flows through the other bulb.

In a parallel circuit, if one of the bulbs is taken out or damaged, the other bulb will still light up.
This is because a part of the circuit is still closed.

This is why light bulbs in houses and other buildings are usually connected in parallel.

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Measuring current

An ammeter is used to measure current.
To correctly measure the current in a circuit, the
ammeter must be connected in series
in the circuit.
The ammeter’s terminals are marked
with positive (+) and negative (–) signs.

The ‘+’ terminal is connected to the ‘+’ terminal of the dry cell, and the ‘–’ terminal is
connected to the ‘–’ terminal of the dry cell through the bulb.

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Measuring voltage

A voltmeter is used to measure voltage.
To correctly measure voltage across a particular
component, the voltmeter must be connected
in parallel to the component.
Again, the two terminals have ‘+’ and ‘–’ signs.

To measure the voltage across a component,

The ‘+’ terminal is joined to the ‘+’ terminal of the dry cell, and the ‘–’ terminal is connected to
the ‘–’ terminal of the dry cell.

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Calculating current in series circuits Page81

In a series circuit, the current at every point of the circuit is the same.
As the number of bulbs increases, the brightness of the bulbs decreases.
If one bulb goes off or is removed, the circuit is broken and no current flows.

Calculating current in parallel circuits

In a parallel circuit:
 current splits into two or more branches.

The total current of the circuit is the sum of the current that passes through each of the branches.
If one bulb is removed, any remaining bulbs in parallel will still light up.
If the bulbs are identical:

 number of bulbs increases the brightness of the two bulbs will be the same.

Calculating voltage in series circuits

Calculating voltage in series circuits

The total voltage is equal to the sum of the voltages across each component in the circuit.

VT = V1+ V2

Total Voltage (V3) = voltage across bulb 1(V1) + voltage across bulb 2 (V2)

Calculating voltage in parallel circuits

In a parallel circuit, current splits up into two or more parts.
BUT, the voltage across any component is the same as the total voltage in the circuit.

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Cells in series Page83

In a simple circuit, as the number of dry cells in series increases, the voltage increases.

The total voltage across all the dry cells is equal to the sum of the voltages of the individual cells.

One cell is 1.5V. Therefore, if three cells, (1.5 x 3)V = 4.5V

Two dry cells face each other, therefore their voltages cancel out each other.
Hence, one cell remaining, which is 1.5V.

Cells in parallel

As the number of identical dry cells in parallel increases, the total voltage across the dry cells remains the
same as the voltage of each dry cell.

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Relationship between voltage and current

As the number of dry cells in series increases, the total voltage increases.

As the voltage in a circuit increases, the current also increases.

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Bulbs in series Page86

If two identical bulbs are connected in series, the current passing through each bulb is the same.
Each bulb will have the same brightness.

Bulbs in parallel

If an identical bulb is added to the circuit in parallel, the current splits into two branches.
Each branch carries a current of 3 A, therefore each bulb has a current of 3 A passing through it.

As a result, each bulb has the same brightness.

Resistance

All electrical components have a property known as resistance, which opposes the current in a circuit.

The S.I. unit of resistance is ohm (Ω).

Resistors are electrical components that can be used to control the size of the current in a circuit.

Types of resistor 2. Variable resistor (Rheostat
1. Fixed resistor

Resistors in Series and Parallel

Resistance in a circuit can be varied by connecting resistors in different ways
i.e. series or parallel.

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Resistors in Series

R1 + R2 = RT
 Resistors in Parallel

Household Wiring and Safety Devices

 Switches

Used to open and close circuits

Open switch

Close switch Page88

 A two-way switch

Bulb A
Bulb B

When switch is at position 1, bulb A lights up.
When switch is at position 2, bulb B lights up.

Electricity at Home

Electrical lighting and appliances are connected in parallel.

If one bulb or appliances are faulty, the others will still work. Page89
In parallel circuit, switches can be used to control bulbs separately

In the circuit above, there is only ONE switch.
If switch is off, both bulbs did not light up.
If switch is on, both bulbs light up.

Switch

A

Switch

B

In the circuit above, there are TWO switches.
If switch A is on & switch B is off, only Bulb A will lights up.
If switch A & B is on, both Bulb A & B will light up.

Fuse

Electrical components and appliances will work when a certain amount of current passes through.
If too much current flows, the component or appliance can be damaged or catch fire.
To prevent this, a fuse is placed in the circuit.

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A fuse is a short length of wire of a certain diameter.
It is made of an alloy of tin and lead. It has a low melting point.
A fuse is connected in series.

A circuit without a fuse

The rating of a fuse is the maximum current that can flow through it without melting.
Choosing the right fuse
The fuse rating that we choose should be slightly higher than the maximum current in the circuit.

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Correct way to wire three-pin plug
New and Old colour codes of the wires

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Safety by Earthing

People who regularly work with high voltage electrical equipment are required to
wear thick rubber shoes.
The resistance of the shoes is so high it would not let current flow to the ground,
through the person.
Thus, they are protected from electric shock.
Overloading
If there are too many appliances connected in parallel to a socket, the current in the mains wire increases, causing it to
get hot. The circuit is said to be overloaded and this may cause a fire.

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Electrical safety rules

We should observe electrical safety precautions to prevent electric shocks and fires.
Do not overload the same power socket with too many plugs.
This will draw a large current and generate heat in the wires carrying the
current to the socket, which may cause a fire.
Do not insert objects other than electrical plugs into power sockets as you
may get an electric shock.
Do not touch electrical appliances
with wet hands.

If the electrical wiring is very old, and the insulation is peeling off, this may
cause electric shocks and fires.

Do not place electrical appliances near wet areas such as the bathroom
and sink.

Disconnect the appliance from the power supply before doing repairs and
maintenance.

It is always safer to call the electrician to repair damaged
electrical equipment.

Page94

CHAPTER 13: ELECTRICITY

TOPIC 13.1: ELECTRIC CIRCUIT

1. Electrons flow in the same direction as conventional current. TRUE / FALSE
(SPE/2011/Q42d)

2. The bulb and cell in the circuits shown in figure below are similar. In which circuit would the bulb light up
the brightest? (SPE/2011/Q38)

3. Nurul carried out an experiment to measure the current in a circuit for different voltages, as shown in
figure below. The resistor, R in each circuit is identical and a milimeter is used to measure the current.

She recorded the readings obtained in the table below.

Circuit Voltage (volts) Current (amperes)
15
Circuit 1 1.5 30
60
Circuit 2 3.0

Circuit 3 X

What is the value of X? (SPE/2012/Q33) Page95
A. 4.5 volts
B. 6.0 volts
C. 7.5 volts
D. 9.0 volts

4. Ismail set up an electrical circuit using two identical resistors, a light bulb and four voltmeters as shown
in figure below.

If V1 is 9.0 V, what would be the reading of voltages V2, V3 and V4?
(SPE/2014/Q33)

V2 (volts) V3 (volts) V4 (volts)
A. 2.0 3.0 4.0
B. 2.5 3.0 3.5
C. 3.5 2.0 3.5
D. 9.0 9.0 9.0

5. Which one is the correct way of connecting ammeter and voltmeter to measure the voltage and current
of the light bulbs?
(SPE/2016/Q29)
A. B. C. D.

6. The diagram shows a circuit with an ammeter connected in series with the dry cells. What is the current Page96
at l2 if ammeter at l1 reads 3.5 A?
(SPE/2016/Q30)

A. 1.5 A
B. 2.5 A
C. 3.5 A
D. 4.5 A

7. Electric current is described as a flow of electrons from the negative terminal to the positive terminal of
a cell. Electrons need a conducting material to flow. (SPE/2009/Section B Q5)

a) What is meant by a ‘conductor’ and name a conducting substance commonly used in electrical wires.
_______________________________________________________________________
_______________________________________________________________________

b) Explain why electrical wires are covered with plastic or rubber?
_______________________________________________________________________

c) Dry cells and batteries are sources of electrical energy.
i) What type of energy is stored in dry cells and batteries?
_______________________________________________________________________
ii) Some batteries are ‘rechargeable’. What do you think are the advantages of using rechargeable
batteries?
_______________________________________________________________________
_______________________________________________________________________

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TOPIC 14: ACID, ALKALIS & SALTS
14.1 ACIDS AND ALKALIS

ACIDS

1. Foods that taste sour contain some forms of acid.
Example: orange contains citric acid.

2. Properties of acids:
 All acids are sour.

 Acids turn blue litmus paper red.

 Most acids are corrosive.

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3. Uses of some common acids:

Type of acid Uses
Sulphuric acid  In batteries
 In making plastics and fertilisers
Nitric acid  In making fertilisers and explosives
Ethanoic acid (vinegar)
 Preserving food and in cooking

4. Making of common acids by dissolving in water:

Hydrochloric acid Formed by dissolving gaseous hydrogen chloride in water
Sulphuric acid Formed by dissolving liquid sulphuric acid in water
Nitric acid Formed by dissolving liquid nitric acid in water

ALKALIS

1. Properties of alkalis:

 All alkalis are bitter.

Soap solution tastes bitter.
This is due to the presence of alkalis in soap.

 Alkalis turn red litmus paper blue.

 Alkalis feel soapy. Page99

The slippery feel of liquid detergents or soaps
comes from the alkalis in them.

This is one of the more obvious feature of alkalis
that distinguishes them from acids.
 Alkalis are corrosive.
Alkalis are corrosive, they can cause severe damage to the skin, eyes and respiratory tract.

2. Uses of some common alkalis: Uses
Types of alkali
 In making soaps and detergent
Sodium hydroxide  In making dyes
Potassium hydroxide
Calcium hydroxide  In reducing soil acidity
 In making fertilisers
Ammonia solution
 In making cleaning liquids

Testing for Acids and Alkalis

1. Indicators are substances that are used to test for the presence of acids and alkalis.

Their presence is usually indicated by a change in colour in the indicators.

2. Some examples of indicators are:

 Litmus

a) Acids turn blue litmus red b) Alkalis turn red litmus blue.

 Universal indicator (also known as pH indicator).

3. Universal indicator shows different colours depending on how acidic or alkaline the substances

are.

Each colour represents a pH value between 0 and 14.

4. Acids have a pH value of _____________________.

The lower the pH value, the stronger the acid.

5. Alkalis have a pH value of _____________________..

The higher the pH value, the stronger the alkali.

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