Express Notes Science Form 3

Written By
Ng Chee Kin
B.Sc.(Hons.), MBA
ngcheekin@gmail.com
mrcheekin@blogspot.com.au

All Rights Reserved ©2012 Ng Chee Kin

PREsSS
E X p r e��

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3. When oxyhaemoglobin reaches the body cells, it 4. The oxygen is then absorbed by the body cells
CHAPTER 1

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breaks down and releases oxygen. for cellular respiration.
Respiration

1.1 Human Breathing Mechanism Oxygen Oxygenated blood returns Oxygenated blood

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to the heart pumped out of the Other
1. The human respiratory system: Heart heart
Oxygen enters blood in body
Blood capillaries
Trachea the lungs cells
around the alveoli

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Deoxygenated blood Deoxygenated blood
Bronchus Lungs pumped out of the heart returns to the heart
Lung
(plural: bronchi)

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Key: Movement of oxygen Haemoglobin
Bronchiole
Movement of oxygenated blood Oxyhaemoglobin
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Movement of deoxygenated blood

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Alveolus
1.3 The Importance of a Healthy Respiratory CHAPTER 2
(plural: alveoli)
Bronchioles .b
System Blood Circulation and Transport
1. Chemical substances which are harmful to the
2. The air flow during inhalation: 2.1 Transport System in Humans
respiratory system are:
in
Nose Trachea Bronchus Bronchiole (a) nicotine, tar and carbon monoxide from 1. The human heart:
Alveolus cigarette smoke
(b) sulphur dioxide, nitrogen oxide, carbon Aorta
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Vena cava
3. The air flow during exhalation: monoxide, asbestos dust, coal dust and Pulmonary artery
hydrocarbons from vehicles and factories. Semilunar
Alveolus Bronchiole Bronchus valves
2. Tar and asbestos dust are carcinogenic, which Pulmonary
Trachea Nose vein
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means they can cause lung cancer if inhaled
Right
excessively. atrium
1.2 Transport of Oxygen in the Human Body Left atrium
3. Bacteria, viruses and other microorganisms
1. The oxygen dissolves in the moist lining of the produce toxins which cause illnesses. Tricuspid Bicuspid
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valve valve
alveolus and then it diffuses into the blood 4. We need to improve the quality of air in order
capillaries. to preserve healthy respiratory system. Left
2. In the blood capillaries, oxygen will combine Right ventricle
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with haemoglobin in the red blood cells to form ventricle
oxyhaemoglobin. Septum

TWB Sci F3 (Exp Note) A 2nd.indd 3 5/26/2009 4:12:56 PM

Pulmonary artery Aorta 4. Path of blood flow in the circulator system: 5. Double circulatory system:
Pulmonary (a) Deoxygenated blood is pumped from the
Vena cava vein
heart to the lungs and oxygenated blood

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Deoxygenated Oxygenated
Right atrium Semilunar blood blood flows back again to the heart.
(b) Oxygenated blood is pumped from the heat

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valves
Vena cava to the rest of the body and deoxygenated
Left atrium Lung
blood flows back again to the heart.
6. Human blood transports many substances in our

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Bicuspid body.
Tricuspid valve Right Left
valve atrium atrium
Septum Substance
Right From To
Left ventricle transported
ventricle

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Right Left Oxygen (in Lungs All body
Cardiac muscle
ventricle Internal organs ventricle the form of cells
(for example, oxyhaemoglobin)
Deoxygenated blood Oxygenated blood liver, gut)
Carbon dioxide All body cells Lungs

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Digested food Small Liver and
2. Functions of the heart: (glucose, amino intestine all body
(a) Pumps blood to all parts of the body. acids) cells

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(b) Transports nutrients and oxygen to the body Rest of the body (for Waste materials Liver and Kidneys
cells. example, head, arms, (such as urea) cells
(c) Transports carbon dioxide and waste
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legs)
materials from the body cells. Hormones Endocrine Target

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3. Types of blood vessels: glands organs

Characteristic Artery Vein Capillary
Structure
Connective
tissue
.b Connective
tissue
2.2 Human Blood
1. Human blood consists of:
in
(a) 55% plasma
Lumen Smooth Lumen Smooth Lumen Endothelium
muscle (b) 45% blood cells and platelets
muscle
2. Types of blood cells:
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Endothelium Endothelium
Type Function

Size of lumen Small Large Very small Red blood cells Carries oxygen from the
lungs to the body cells
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Thickness of wall Thick, muscular, elastic Thin, less elastic, Only one cell thick and
White blood Defends the body against
muscular not muscular
cells diseases
Speed of blood flow Rapid Slow Very slow Platelets Helps in blood clotting
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Blood pressure Very high pressure Low pressure Very low pressure 3. Functions of blood:
(a) Transports gases and dissolved substances
Presence of valves No except at aorta and Yes No
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(b) Protects the body against diseases
pulmonary artery (c) Maintains the body temperature at 37oC


4. Compatibility of blood groups: 4. Transpiration is the process by which plant loses 3.2 The Urinary System in Humans
water, in the form of water vapour.
Recipient’s blood
5. Transpiration happens through the stomata

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Donor’s group A B AB O Vena cava Aorta
(singular: stoma), tiny pores on the leaves of
blood group
the plant.

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Adrenal
A     6. Factors that affect the rate of transpiration: Renal gland
(a) Light – the brighter the light, the greater vein
B     Renal
the rate of transpiration.

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AB     artery
(b) Temperature – the higher the temperature,
O     the greater the rate of transpiration. Right Left
(c) Humidity – the lower the humidity, the kidney kidney
5. Universal donor is a person with blood group O. greater the rate of transpiration.
6. Universal recipient is a person with blood group

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(d) Wind – the faster the movement of air, the Ureters
AB. greater the rate of transpiration.
7. Transpiration helps plants to absorb and transport Urinary
2.3 Transport System in Plants water and minerals. bladder

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1. The transport system in plants is called the
Urethra
vascular system.
2. There are two main vascular tissues: CHAPTER 3
(a) Xylem- transports water and mineral salts
Excretion

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from the roots to the leaves 
Cortex
(b) Phloem- transports glucose from the leaves 
3.1 Human Excretion
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to all parts of the plants 


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3. Xylem and phloem are found in the vascular 1. Excretion is a process of eliminating waste Cortex 
Medulla
bundle. products from the body. 
Xylem Medulla 
2. The organs responsible for removing waste 


.b


products are called the excretory organs.



Renal artery



3. The waste products removed from the body are
Phloem Pyramid
called the excretory products.
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Cross section of leaf Renal vein
Pelvis
Epidermis Excretory organ Excretory products
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Phloem vascular
Xylem bundle Skin Water, mineral salts, urea
Ureter
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Lungs Water, carbon dioxide
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Cross section of stem
Kidneys Water, mineral salts, urea 1. The human urinary system consists of: kidney,
Root hair ureter, bladder and urethra.
Cortex 4. Excretion helps to maintain the balance of water 2. Functions of kidneys:
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Endodermis content, chemical composition and pH in the (a) To filter blood.
Xylem body system. (b) To remove urea, excess mineral salts and
Phloem water to form urine.
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Epidermis (c) To control the balance of water and chemical
Cross section of root in the body.


3. Kidney failure happens when the kidneys of 6. Most nitrogenous wastes are very poisonous. 4.2 Male Reproductive System
a person unable to perform their functions 7. Some excretory products of plants are useful
properly. to humans such as: morphine, opium, cocaine,

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Organ Function
4. Kidney failure can be treated through dialysis tannins and oils.
or kidney transplant.

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Testis (plural: • Produces sperms (the male
5. Dialysis is a method used to filter and remove testes) gametes)
waste products from the blood of a patient. CHAPTER 4 • Produces male sex hormones
Reproduction

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3.3 Excretion in Plants Scrotum • Holds and protects the testes
1. Plants excrete waste products mainly through 4.1 Understanding Sexual and Asexual
Sperm duct • Transports sperms from the
simple diffusion. Reproduction
(vas deferens) testes to the urethra inside
2. Excretion in plant is mainly done through the

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1. Reproduction is a process of producing new the body
cell wall and stomata.
individuals by living organisms.
3. Mineral salts such as calcium carbonate and
2. Importance of reproduction: Urethra • Allows sperms to flow out of
calcium oxalate are retained in the plant as
(a) To increase the number of individuals of the the body
crystals.

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same species.
4. Minerals such as silicon salts are deposited in the
(b) To ensure certain species does not become Penis • Transfers semen into vagina
leaves to strengthen the leaf blade.
extinct. during copulation
5. Nitrogenous waste products are removed when
3. Types of reproduction:

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plants shed their leaves, flowers or bark.
Seminal • Secrete fluid which contains
vesicles nutrients for the sperms
Reproduction
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Sexual Asexual 1. Sperm:
(Involving the male and the female gametes) (a) It is the male sex cell.

Animals Plant
Binary fission
(bacteria)
.b Regeneration
(planaria)
Budding
(yeast)
(b) It is produced by the testes.
(c) It is also the smallest cell in the males’
body.
in
(sperm and ovum) (pollen grain Spore formation Vegetative (d) It is shaped like a tadpole, which has a head,
and ovule) (moss, ferns and fungi) reproduction neck, middle piece and tail.
(e) The head contains a nucleus which has
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genetic material.
(f) The tail helps the sperm to move or swim in
Seminal vesicle Vas deferens
Seminal the female reproductive system.
Vas deferens vesicle 2. Males reach puberty at 12 to 14 years old, which
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Prostate gland
is later than girls.
3. There are physical, emotional and physiological
Epididymis
Urethra Prostate changes during puberty.
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Urethra gland 4. The testes start to produce sperm and male sex
Penis Penis
hormones during puberty.

Testis Scrotum
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Scrotum
Testis


4.3 Female Reproductive System 1. Ovum (plural: ova): (c) Fertile phase / ovulation phase (day 12 to 16)
(a) It is the female sex cell. (d) Premenstrual phase (day 17 to 28)
Oviduct (Fallopian tube) (b) It is produced by the ovary. 6. Women of about 50 years of age undergo

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(c) It is the largest cell in the females’ body. menopause when their menstruation stops.
(d) It is spherical in shape, which contains a

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nucleus and cytoplasm. 4.5 Fertilisation and Pregnancy
(e) The nucleus contain genetic material.
Ovary
(f) It cannot move by itself. 1. Fertilisation is the fusion between the sperm and

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the ovum.
Uterus
4.4 Menstrual Cycle 2. Development of an embryo into a foetus until
Cervix birth:
1. Menstrual cycle is the changes in a woman’s ovary Sperm Ovum
Vagina and uterus over 28 days.

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2. Menstrual cycle involves ovulation and Fertilisation
menstruation which happen regularly each
Zygote
Ovary Oviduct (Fallopian tube) month.
3. Ovulation happens when an ovary releases a

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mature ovum. Embryo
Uterus 4. Menstruation is the shedding of the uterine wall Implantation
and blood through the vagina.
Foetus

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5. Menstruation can be divided into four stages:
Cervix (a) Menstruation phase (day 1 to 5) Childbirth
(b) Repair phase (day 6 to 11) Baby
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Vagina A zygote is formed

Urethra Eight-cell Four-cell Two-cell

Ovary
Organ Function
• Produces ova (the female
.b An embryo is formed
stage stage stage
in
The ovum is fertilised (fertilisation)
gametes) Embryo moves
towards uterus
• Produces female sex hormones Ovary Fallopian tube
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Fallopian • Place of fertilisation
tube (oviduct) Ovary produces an ovum (ovulation)

Uterus • Place for the implantation of
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(womb) zygote Uterus Embryo attaches to
• Place where the foetus uterine wall (implantation)
develops and grows
Cervix • Widens during childbirth 4.6 Importance of Prenatal Care 4.7 Importance of Research in Human
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Vagina (birth • Place where the sperms are Reproduction
1. Pregnant women need to take enough nutritious
canal) deposited during copulation food and have a balanced diet. 1. Sterility (infertility) is the inability to produce
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• Baby is born through this 2. Pregnant women should avoid smoking, taking children.
birth canal alcohol or drugs. 2. Methods to overcome sterility:


(a) Drug treatment (such as hormones) 2. Germination happens when the embryo grows
Structure Function
(b) Surgery into a seedling.
(c) In vitro fertilisation (IVF) Ovary To protect the ovule 3. Seeds need air, water and suitable temperature

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3. Methods for birth control (contraception): Ovule Contains ova (the female gametes) to germinate.
(a) Contraceptive pills

.a
(b) Rhythm method (natural method) Anther Contains pollen grains (the male gametes) 4.12 Vegetative reproduction in Flowering
(c) Using a condom Filament To support anther Plants
(d) Using a diaphragm

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1. Vegetative reproduction is a method of producing
(e) Intrauterine contraceptive device (IUCD) 4.9 Pollination
new plants from any vegetative parts of the
(f) Vasectomy – sperm ducts cut and tied
1. Pollination is the transfer of pollen grains from parent plant.
(g) Ligation (tubectomy) – oviducts cut and tied
the anther to the stigma. 2. Vegetative reproduction is an asexual
2. Self-pollination and cross-pollination: reproduction.

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4.8 Sexual reproductive System of Flowering Plants
Pollen grains Stigma 3. Vegetative parts that can reproduce are: stem,
1. Struture of a flower: leaf and root.
Pollen grains Anther 4. Tissue culture and stem cuttings are techniques
Flower used to produce new plants.

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Stamen Pistil
CHAPTER 5

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Anther Filament Ovary Stigma Style Growth
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Pollen grain Ovule 5.1 Human Growth Pattern

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One plant Another plant of 1. Growth is an irreversible and permanent process
Petal the same species in living things.
Pistil Key: 2. Growth in humans can be determined by
Stamen

Anther
Stigma
Style
.b Self-pollination

4. Agents of pollination:
Cross-pollination measuring the height and weight.
3. Growth curve is divided into five stages:
(a) Infancy (d) Adulthood
in
Filament Ovary (a) Wind (c) Insects
(b) Childhood (e) Old age
Ovule (b) Animals (d) Water
(c) Adolescence
Nectary Sepal
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Receptacle 4.10 Development of Fruits and Seeds in Plants
Pedicel Infancy Adolescence Old age
1. Fertilisation occurs when the male gamete fuses Childhood Adulthood
Structure Function with the ovum in the ovule.
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Minimal
Sepal To protect flower during the bud stage 2. A zygote is formed when the ovum is fertilised Negative

Height (cm)
growth
by the male gamete. Slow growth
Petal To attract insects or animals 3. After fertilisation, the ovule will develop into a growth Rapid
growth
Stamen The male reproductive part seed and the ovary become the fruit.
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Pistil The female reproductive part
4.11 Germination of Seeds Rapid
Stigma To receive pollen grains growth
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1. A seed is made up of an embryo and a food
Style To support stigma Age (years)
store wrapped in a testa (seed coat). 0 3 13 20 65


2. Silicon always exists in the form of compounds
CHAPTER 6
such as silicas and silicates.
Land and Its Resources

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3. Silica is silicon dioxide, which consists of silicon
and oxygen.

.a
6.1 Minerals in the Earth’s Crust 4. Silicate is made up of silicon, metal and oxygen.
5. Properties of silicas and silicates:
1. Minerals are solid elements or compounds found naturally. (a) Insoluble in water
2. Elements present in various minerals:

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(b) Do not react with acid
(c) Do not break down when heated
Oxide Carbonate Sulphide Silicate
(d) Very stable and are not eroded easily
Iron China Calcium
Element Cassiterite Haematite Calcite Malachite Galena
pyrite clay silicate 6.4 Calcium Compounds

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Tin  1. Properties of calcium carbonate:
Iron   (a) Insoluble in water
(b) Reacts with dilute acids to produce salt, water
Calcium  

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and carbon dioxide
Copper  (c) Breaks down into calcium oxide and carbon
Lead  dioxide when heated
2. Quicklime (calcium oxide) is formed when calcium
Aluminium 

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carbonate is heated strongly.
Silicon   3. Slaked lime (calcium hydroxide) is formed when
calcium oxide is added with some water.
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Oxygen      
4. Limewater (calcium hydroxide solution) is formed

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Carbon   when slaked lime is added with more water.
Sulphur  
6.5 Natural Fuel Resources and Their Importance
3. Properties of minerals:
Properties Description
.b
(b) Metals react with sulphur to form metal
sulphide
1. Fossil fuels include petroleum, natural gas and
coal.
in
Reaction Reaction 2. Petroleum:
Hardness Most mineral are hard (a) Formed from organism remains buried in
Metal rate with rate with
Solubility Most minerals are insoluble in oxygen sulphur sediment under heat and high pressure.
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in water water (b) It contains many types of hydrocarbons which
Magnesium Very fast Very fast can be separated by fractional distillation.
Action of • Most metal oxides are stable
Aluminium Very fast Very fast (c) The components of petroleum produced by
heat • Metal sulphides break down
fractional distillation are called fractions (or
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into metal oxide and release Zinc Fast Fast
distillates).
sulphur dioxide gas Iron Fast Fast (d) Different fractions are obtained due to
Copper Slow Slow different boiling points.
6.2 Reactions Between Metals and Non-metals
• the greater the boiling point, the darker
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1. Metals react with non-metals at different rates 6.3 Silicon Compounds the colour of the fractions
to form stable compounds: • the greater the boiling point, the more
1. Silicon is the second most abundant element in viscous the fractions
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(a) Metals react with oxygen to form metal
oxide the Earth’s crust.


• the greater the boiling point, the more 2. Electrical charges can be produced through Electron flow
soot is produced when the fractions are friction between two objects.
burnt 3. Matters are made up of small particles called

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• the greater the boiling point, the harder atoms.
the fractions burn

.a
Electron (negatively charged)
Product of
Uses
distillation

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Petroleum gas Cooking gas Proton (positively charged) (b) Direction of electron flow

Petrol (gasoline) Fuel for vehicles
Neutron (no charged) The flow of electric current and electron
Naphta For making plastics
and polyvinyl chloride

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(b) Voltage
(PVC) Structure of an atom – the electrical force needed to move
Kerosene Fuel for aircraft electrical charges from one point to other
4. An atom has two charged particles: in a conductor.
Diesel oil Fuel for lorries and

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(a) Electrons, which have a negative charge (–) (c) Resistance
buses
(b) Protons, which have a positive charge (+) – characteristic that resists the flow of electric
Lubricating oil Lubricants for 5. Neutrons in an atom have no charge because current in a conductor.
machines they are neutral.

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Fuel oil Fuel oil for ships 6. An atom becomes positively charged when it 7.3 Electric Current, Voltage and Resistance
loses electrons.
Bitumen To seal roads 1. Measuring current (symbol: I):
7. An atom becomes negatively charged when it
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– connect an ammeter in series with other
gains electrons.

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3. Natural gas: electrical components in a circuit.
(a) consists of 90% methane, 10% of mixture of – the deflection of the pointer of the ammeter
7.2 Electricity
ethane, propane, butane and pentane. shows the value of current flowing through
(b) It is usually found together with the
petroleum.
(c) It is used as fuel source and to produce
.b
1. Electricity is a form of energy. It is also called the
electrical energy.
2. Electrical energy can be generated by generators
the components.
– the SI unit for electric current is ampere
(symbol: A).
in
fertilisers. and electric cells. 2. Measuring voltage (symbol: V):
4. Coal: 3. Current, voltage and resistance: – connect a voltmeter in parallel to other
(a) Made up of carbon, oxygen, nitrogen and (a) Current electrical components in a circuit.
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sulphur. – the rate of flow of charges. – the deflection of the pointer of the voltmeter
(b) It is formed from plant remains that grew in – flows from the positive terminal to the shows the value of voltage across the
swamps. negative terminal of a battery. components.
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– the SI unit for voltage is volt (symbol: V).
Current
3. The SI unit for resistance (symbol: R) is the ohm
CHAPTER 7 (symbol: Ω).
Electricity
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7.4 The Relationship Between Current, Voltage
and Resistance
7.1 Electrostatics
1. Resistor is an electrical component that resists
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1. Electrostatics is the study of static electrical
(a) Direction of electric current flow the flow of electric current.
charges.

TWB Sci F3 (Exp Note) B 2nd.indd 10 5/26/2009 4:12:30 PM

2. Ohm’s Law: 2. Advantages of a series circuit:
Electrical
– the current flowing through a conductor is Symbol (a) When more cells are added to the circuit,
component
directly proportional to its voltage. the voltage and current increase. Hence, the

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Rheostat bulbs glow brighter.
Voltage (V) (Variable or or (b) Bulbs light up with equal brightness because

.a
Resistance (R) = —————–
Current (I) resistor) the current flows through each bulb is the
same.
– the greater the resistance, the smaller the Fuse
3. Disadvantages of a series circuit:

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current.
Galvanometer G
G
(a) If one of the bulbs is fused (burned out), the
– increasing the voltage supplied will increase G
V
other bulbs will not light up.
the current in the circuit. Voltmeter V
V (b) The brightness of the bulbs decreases when
A more bulbs are connected in series, because
A
A
7.5 Electric Circuits Ammeter

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the electrical energy is shared by more
1. An electric circuit is a path which allows an bulbs.
4. Comparison between series and parallel
electric current to flow through.
circuits: 7.7 Parallel Circuit
2. A simple electric circuit is made up of 3

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components: Series circuit Parallel circuit 1. Current, voltage and total resistance in parallel
(a) A cell (a source of electrical energy)
• Has only one path • Has more than one circuit:
(b) A bulb (a resistor)
for current to flow path for currect to 2. Advantages of a parallel circuit:
(c) Connecting wire (a conductive path)

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through flow through (a) When one of the bulbs is burned out, the
• Light bulbs do not • Light bulbs glow other bulbs will still light up.
Dry cell
glow as bright as brighter than (b) Each electrical component can be controlled
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those connected in those connected in by separate switches.

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Wire (c) All bulbs will light up with the same
parallel series
brightness.
• If one light bulb • If one light bulb
Light bulb .bburns out, the
circuit becomes
incomplete. Hence,
burns out, other
light bulbs will still
light up.
V
V V1
I = I1 + I2
in
other light bulbs I
An electric circuit V V = V1 = V2
will not light up. I1
3. Symbols of electrical components: R1
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7.6 Series Circuit I2 R2 1 1 1
—=—+—
Electrical R R1 R2
Symbol 1. Current, voltage and total resistance in series
component V
circuit: V2
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Electric cell
V
Battery (more I = I1 = I2 = I3 3. Disadvantage of a parallel circuit:
V
than one cell) (a) When more bulbs are connected in parallel,
the dry cells will become weak quicker.
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Switch I
V = V1 + V2 + V3
I1R1 I2R2 I3R3
7.8 Magnetism
Bulb or
R = R1 + R2 + R3
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V V V 1. Magnetism is the properties and effects of
Resistor or V1 V2 V3 magnetic substances.


2. Magnetic field is the area around a magnet where Copper wire (c) Gas turbine generator
a magnetic force can be detected.
3. The magnetic field of a magnet can be represented Combustion

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Switch Card Air
chamber
by lines, called magnetic field lines. filter
Exhaust
4. The magnetic field lines have a certain pattern Compressor

.a
Electric tower
and direction.
(a) The pattern of the magnetic field lines can Retort
stand
be shown by using iron filings.

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Compass Motor
Power pack Spark plug Gas turbine Generator

Iron filings
CHAPTER 8 (d) Diesel power plant
Magnet
Cardboard

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placed Generation of Electricity
under the
cardboard
8.1 The Generation of Electrical Energy electric
current

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(b) The direction of the magnetic field lines can 1. Types of generators:
be detected by using a compass. (a) Hydroelectric power plant
Diesel engine Generator

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Dam (e) Nuclear power plant
Pylon
N Concrete wall
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Compass Magnetic Water
field lines

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S Control Steam
rods
turbine
Steam Electrical

5. Characterstics of magnetic field lines:
(a) Run from the north pole to the south pole
.b Tunnel Turbine and generator
Output

Condenser
in
(b) Thermal generator Reactor
of the magnet.
(b) Do not cross one another. Pump
Boiler Water
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Steam Pylon
Steam
7.9 Electromagnetism generator Pump
Pump
1. Electromagnetism refers to the properties and Turbine Water
27ºC 38ºC
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effects of electromagnets produced by electric
Generator
current.
2. An electromagnet is a magnet that is produced
by the flow of electric current. 8.2 Transformers
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(a) Without electrical energy, an electromagnet Sea water
Water 1. A transformer is a device for changing the voltage
loses its megnetism.
of an alternating current.
(b) An electromagnet is a temporary magnet. Burner Condenser 2. An alternating current (symbol: a.c.) flows back
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3. A straight line conductor carrying current produces
From water purification plant and forth, reversing its direction.
a concentric magnetic field lines around it.


3. Types of transformers: (b) Step-down transformer 1. National Grid Network is a system of high voltage
(a) Step-up transformer circuits that connects the main power stations.
Soft iron core 2. Advantages of National Grid Network:

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Soft iron core
(a) Ensures continuous and uninterrupted
electrical power supply to the consumers.

.a
a.c. a.c. a.c.
a.c. input output (b) Reduces the operational cost of electrical
input output
voltage voltage voltage
voltage energy transmission.
(c) Prevents wastage of electrical energy.

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Primary coil Secondary coil
Primary coil Secondary coil
8.4 Electrical Power Supply and Wiring system in
– To increase the output voltage. – To reduce the output voltage. Homes
– The secondary coil has more turns than – The secondary coil has less turns than the
1. Homes are supplied with 240 V alternating

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the primary coil. primary coil.
current (a.c.).
8.3 Electrical Power Transmission and Distribution System Part Function
Transmission over Mains Breaks the circuit when current

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long distances fuse exceeds a safe value

Transmission
A 132 kV/ Components:
Mains Cuts off electrical power supply

system
275 kV/ A – Power
C station switch from the mains when electricity
11 kV 500 kV

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A B – Step-up is not needed
B transformer
C – National Circuit Cuts off the electric current that
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240 V/ Heavy Grid breaker flows under abnormal conditions
D

Distribution
415 V 33 kV 33 kV industrial Network

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E E area Live wire Carries the electric current from

system
D – Step-down
transformer the substation to the house
E – Branch
Neutral Carries the electric current from

Residential Shopping Hospital
.b
33 kV 11 kV

Light
substation
wire
Earth
the house back to the substation
Connects an electrical appliance
in
area complex industrial area wire to the earth or ground
Electric Measures the amount of
Branch Heavy
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meter electricity used
substation 33 kV industrial area
2. Our home uses single-phase wiring system.
Branch Light 3. The commercial and industrial areas use three-
Main
National substation industrial area phase wiring system.
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Power Step-up Switch substation 11 kV
Grid 4. 3-pin plug:
stations transformer zone (Step-down
Network Branch Residential Fuse
transformer) Cover removed
11 kV 132 kV/ substation area
275 kV/ 132 kV/ 240 V
275 kV/ 132 kV/
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500 kV 275 kV/ Earth wire
500 kV Branch Shopping
500 kV Neutral wire Cover
substation 415 V complexes
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Generation Transmission system Distribution system Cable Live wire


3. Types of fuses:
3-pin plug
(a) Replaceable wire fuse
CHAPTER 9
(b) Cartridge fuse Stars and Galaxies

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Live Neutral Earth Metal
9.1 The Sun

.a
Fuse cap Fuse wire
wire wire wire
Glass tube 1. The Sun is a star that is closest to the Earth.
2. Characteristics of the Sun:

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Carries Carries Carries Prevents (a) It is the centre of the solar system.
Cartridge fuse
current current leakage excessive (b) It is the only star in the solar system.
from the from the current current Fuse wire (c) It is mainly made of hydrogen (70% to 80%)
substation house from the flowing Contact and helium.
Contact
to the back appliances into the 3. Structure of the Sun:

t.c
house to the to the appliance
substation Earth and Holder
damaging it Prominence
Replaceable wire fuse
Corona

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4. Fuses have different ratings, according to the
• A 3-pin plug carries electric current from a maximum current they can carry. For example, Chromosphere
power station to an appliance in use, and 1 A, 2 A, 3 A, 5 A, 10 A and 13 A. Sunspots
then returns it to the substation. Photosphere

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• A 3-pin plug also acts as a safety device to 8.7 Safety Precautions in the Use of Electrical
protect an appliance in use from getting Energy
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Solar flare Core
damaged.
1. Damaged appliances must be repaired by qualified

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electrician only.
8.5 Cost of Electrical Energy Usage (a) Corona (outermost layer) is seen only during
2. Avoid overloading a power point.
a total solar eclipse.
Energy used (J)
1. Power (W) = ———————–
Time (s)
2. Power (P) = Voltage (V) × Current (I)
.b
3. Avoid touching switches, wires or plugs with
wet hands, as this may cause electric shock or
electrocution.
(b) Chromosphere (middle layer) appears reddish
during a solar eclipse.
(c) Photosphere (innermost layer) is the Sun’s
in
4. Install Earth Leakage Circuit Breaker (ELCB) and
3. Energy (kWh) = Power (kW) × Time (h) surface as seen from the Earth. It has sunspots,
Miniature Circuit Breaker (MCB) in home wiring
prominences and solar flares.
1 unit of electrical energy = 1 kWh system for additional protection against electrical
(d) Core (centre of the Sun) is the place where
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accidents.
nuclear fusion takes place, that is, hydrogen
8.6 Fuse and Earth Wire
is changed into helium, releasing a lot of
8.8 Conserving Electrical Energy
1. Fuse and earth wire are protection devices. energy.
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(a) Fuse breaks off the electrical circuit. 1. We need to conserve electrical energy to prevent (e) Sunspots (dark patches) are cooler and they
(b) Earth wire ensures the leakage of current wastage. can cause changes in the Earth’s climate, such
flows to the ground. 2. Ways to conserve energy: as extreme drought.
2. Function of the fuse: (a) Use fluorescent lamps instead of incandescent (f) Prominences are ‘giant flares’ which are huge
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(a) A fuse has a piece of short wire which has light bulbs. columns, extending thousands of kilometres
a low melting point. (b) Use energy efficient electrical appliances. from the surface. It produces solar wind and
(b) When excess current flows through it, the (c) Use the washing machine with a full load. causes aurora.
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wire in the fuse melts and disconnects the (d) Switch off electrical appliances when they (g) Solar flares are huge clouds of hydrogen that
current. are not in use. explode violently on the Sun’s surface. They


also change the Earth’s climate and affect (e) The death of a large star:
Types Description
the telecommunication systems on Earth.
Red giant → Supergiant → Supernova → Irregular-shaped • It has a diameter between

u
Neutron star galaxy 25 000 and 32 000 light
9.2 Stars and Galaxies in the Universe
(f) The death of a super-large star: years.

.a
1. Stars: • It does not have a definite
(a) Made up of dust and gases (such as hydrogen Red giant → Supergiant → Supernova → pattern or shape.
and helium). Black hole • It exists in various different

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(b) Generate heat and light through nuclear forms and is usually made
6. Galaxies:
fusion. up of young stars that are
(a) Are collection of billions of stars, planets, dust
(c) Differ in size, brightness, colour and very hot.
and gases held together by a gravitational
temperature. • Example: Large Magellanic
force
2. Arrangement of stars in ascending order of Cloud

t.c
(b) Types of galaxies:
temperature:
Red → Yellow → White → Whitish-blue → Blue Types Description 7. The Milky Way:
Elliptical-shaped • It has a diameter between (a) It is a spiral-shaped galaxy.
3. Arrangement of stars in ascending order of

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galaxy 3000 and 10 000 light years. (b) The solar system is located in the Milky
size: Way.
• It looks like a smooth,
Neutron star → White dwarf star → Dwarf star round and oval-shaped disc, 8. The Universe:
→ Giant star → Supergiant star and has no arms. (a) It consists of all the matter, energy and space

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• It is the brightest at the that exist.
4. Formation of stars: (b) It has billions of galaxies, stars, planets and
core and gradually fades
(a) Stars are formed from nebulae (singular: particles.
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towards the edge.
nebula), which are made of clouds of dust (c) Its size is infinitive and unknown.
• It is made up of old yellow

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and gases.
stars and does not contain
(b) The nebula contracts when the gases and 9.3 The Universe as a Gift from God
gas and dust, so new stars
dust exert a strong gravitational force on
are not formed.
each other.
(c) Further contraction causes the ball to become
denser until hydrogen atoms fuse to form
.b • Example: M87 in the centre
of Virgo cluster.
1. The Universe is a unique creation of God.
2. Everything that exists in the Universe is not
permanent: Stars are born and die out, new stars
in
helium atoms – a nuclear fusion reaction. Spiral-shaped • It has a diameter of about are formed to replace them.
(d) The reaction causes the temperature to rise galaxy 20 000 to 100 000 light years.
and causes the star to expand. • It is disc-shaped and made
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(e) The balance between the contraction and up of stars gathering in CHAPTER 10
expansion of star will form a stable star, such a whorl with spiral arms
as the Sun. at the edges. These arms Space Exploration
contain dust and gases.
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5. The death of stars: 10.1 Developments in the Field of Astronomy and
(a) When nuclear fusion no longer takes place, • It has a bright centre. Its
Space Exploration
the size of the core of the star will reduce. centre has older stars. Its
(b) The size of a star determines its lifespan. arms have younger stars, 1. Astronomy is the study of objects in the
while dwarf stars and
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(c) Massive stars have longer lifespan than Universe.
smaller ones. nebulae. The arms rotate 2. The Greeks:
(d) The death of a medium-sized star: around its centre. (a) The first people to study astronomy.
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• Example: The Milky Way, (b) First to declare that the Earth is spherical,
Red giant → White dwarf → Black dwarf Andromeda and the orbits of the planets are circular.


3. The Islamic astronomers studied the rotation of
the Earth and the eclipses of the Sun and the
Moon.

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4. Other developments:
(a) Hans Lippershey invested a telescope.

.a
(b) Galileo Galilei was the first man to observe
objects in space with a telescope.
(c) Yuri Gagarin was the first person in space.

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(d) Neil Armstrong was the first human to set
foot on the Moon.
(e) Aristotle believed wrongly that the Earth was
the centre of the Universe.
Space probe

t.c
(f) Claudius Ptolemy supported Aristotle’s
belief that the Earth was the centre of the
Universe.
(g) Nicholas Copernicus (The father of the

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modern astronomy) stated that the Sun is Satellite
the centre of the solar system.
5. Technology used in space exploration: 6. Types of satellites:
(a) Space telescope (such as Hubble Space (a) Communication satellites – enable instant

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Telescope) – helps scientists to discover radio and telephone communication, live
distant objects telecast and Internet applications
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(b) Space probes – send images and data back (b) Weather satellites – enable meteorologists to
to Earth for analysis predict weather hazards such as hurricanes

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(c) Space station – allows scientists to work in and floods
space for a long period of time (c) Navigation satellites – guide ships and
(d) Space shuttles – carry astronauts to repair aircraft
and retrieve damaged satellites in space
(e) Satellites – unmanned devices which are
placed in the orbit of the Earth to carry out
.b Space station
(d) Military satellites – improve national security,
defence and spying systems
(e) Environmental satellites – detect world’s
in
certain functions. resources
7. Remote sensing is the means of using satellites
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to study the conditions on Earth from space.
8. Remote sensing can be used in geology,
agriculture, forestry, disaster management and
national security management.
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Space telescope Space shuttle


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