• SIMPLE MACHINE
• METABOLISM IN THE HUMAN BODY
• SENSE ORGANS
• RESOURCES FROM LIVING THINGS
• SOIL
• ETHICAL ISSUES IN SCIENCE AND DEVELOPMENT
• FAMILY LIFE EDUCATION (TEENAGE PREGNANCY)
• RADIOACTIVITY
• FAMILY HEALTH EDUCATION (ABORTION)
• BASIC ELECTRONICS

Simple Machine

Basic Science JSS3 Third Term

Week 5

Topic: Simple Machine

Introduction

A machine is any instrument you use to make work easier. Any device that makes it easier for us to do work is a machine. The purpose of a machine is to do work more conveniently. The purpose of a machine is to make life easier for you and me. Simple machines only have one part and are used to exert or direct a force. As machines get more complicated they have an increasing number of parts which all work together to do a job.

Types of Simple Machine

Basic machines from which all others are made up are:

• The Lever
• The inclined plane
• Others include the screw, the wedge, the pulley, and the wheel and axle.

Mechanical Advantage

Mechanical advantage is a way of comparing the amount of force needed when you don’t use a device for a task with the amount needed when you do use one. Usually a mechanism has a mechanical advantage greater than 1. For example, a pulley may have a mechanical advantage of 2. This means that using a pulley to lift a load takes half the force than you would need to use if you were lifting the load by yourself. In other words, the pulley can lift twice the load that you could by yourself.

To calculate mechanical advantage you need to know the input force and the output force.

M.A = Output force / Input force

Both input and output force are measured in Newtons (N)

Velocity Ratio (V.R)

Velocity ratio is another important concept of machine. You may have heard of velocity and speed before. Speed describes how fast something is moving. A car is moving at 100km/h. Velocity described how fast something is moving and what direction it is traveling. The velocity ratio represents the ideal mechanical advantage of a machine if friction did not exist.

Velocity ratio is calculated by dividing the input distance by the output distance.

V.R = Input Distance / Output Distance

Calculating Mechanical Advantage and Velocity Ratio

Example 1: A gear moves a conveyor belt with 30N of force when 5N of force is put into the gear. What is the mechanical advantage of the gear?

Solution

M.A  =  Force Output / Force Input

           =  30/5

           =  6

Example 2: A pulley system lifts a load 5m when the rope is pulled 10m by two people. What is the velocity ratio of the pulley system?

Solution:

V.R  =  Distance Input / Distance Output

         =  10/5

         =  2

Efficiency

Efficiency can be used to describe how well a mechanism runs. It is the ratio of the work output of a machine to the work input. Any mechanism, such as a pulley lifting an object, loses some energy. Usually, the energy is lost as heat because of friction. The more energy that is lost, the less efficient the mechanism is. Some of the reasons why machines are not likely to be 100% efficient is because of friction, wear and tear and amount of heat generated as we use the machine. So, a mechanism that is 40% efficient losses more energy than another mechanism that is 70% efficient.

The percent Efficiency can be calculated by dividing the M.A by the V.R.

Efficiency  =  Mechanical Advantage / Velocity Ratio  x  100

Example 3: A pulley has a velocity ratio of 3 and a mechanical advantage of 2. Calculate its efficiency.

Solution:  Efficiency = M.A / V.R  x  100

                                     =  2 / 3  x  100

                                      =  66.67%

Simple Machines

Levers

A lever is a simple machine that allows you to gain a mechanical advantage in moving an object or in applying a force to an object. It is considered a “pure” simple machine because friction is not a factor to overcome, as in other simple machines.

Parts of a Lever

A typical lever consists of a solid board or rod that can pivot about a point or fulcrum. A force or effort is applied, resulting in moving or applying force to a load. The distance from the applied force or effort force to the fulcrum is called the effort arm and the distance from the load to the fulcrum is called the load arm.

Since there is typically a very small amount of friction at the fulcrum, overcoming friction is not a factor in a lever as it might be in another simple machine like a ramp or wedge. Thus, we consider a lever a pure simple machine.

Three Lever Classes

There are three types or classes of levers, according to where the load and effort are located with respect to the fulcrum.

Class 1

A class 1 lever has the fulcrum placed between the effort and load. The movement of the load is in the opposite direction of the movement of the effort. Note that the length of the effort arm can be greater than, equal to or less than the length of the load arm in a class 1 lever.

Class 1 lever

Examples of class 1 levers include:

• Teeter-totter
• Catapult
• Scissors
• Pair of pliers

Double class 1 lever

A scissors and a pair of pliers are considered double class 1 levers.

Class 2

A class 2 lever has the load in between the effort and the fulcrum. In this type of lever, the movement of the load is in the same direction as that of the effort. Note that the length of the effort arm goes all the way to the fulcrum and is always greater than the length of the load arm in a class 2 lever.

Class 2 lever

Examples of class 2 levers include:

• Wheelbarrow
• Crowbar
• Nut cracker

Class 3

A class 3 lever has the effort in between the load and the fulcrum. Both the effort and load are in the same direction. Note that the length of the load arm goes all the way to the fulcrum and is always greater than the length of the effort arm in a class 3 lever.

Class 3 lever

Examples of class 3 levers include:

• Stapler
• Mousetrap
• Broom
• Hockey stick

Wedge

A wedge is really an inclined plane turned on its side. But instead of helping you move things to a higher level, a wedge helps you push things apart. The blades of a knife or a shovel are both wedges. A wedge can also be round, like the tip of a nail, or the tines on your fork. Basically, the wedge works just like a ramp: The narrower the wedge (or the sharper the point of a wedge), the easier it drives it in and pushes things apart. To split something apart really wide, you have to push the wedge a long distance.

Inclined Plane

An inclined plane is a flat, sloping surface. Inclined planes are used to make the job of moving heavy objects easier. An object can go up an inclined plane or down.

Objects usually move straight up and down. This takes the most work and is harder if objects are heavy. With an inclined plane, the slope makes it easier to push or pull the object.

Screw

A screw is a simple machine made up of another simple machine. It is an inclined plane wrapped around a cylinder.

Picture a typical screw:

The screw thread has 4 parts: the head, the body shape, diameter and the pitch.

Screws hold down objects and hold them together. They can be used to press or crush objects too.

Pulley

A Pulley is a simple machine made up of a wheel and a rope. The rope fits into the wheel and one end of the rope is attached to the load. When you pull on one side of the pulley, the wheel turns and the load moves.
We use pulleys because they let you move loads up, down or sideways. They are good for moving objects in hard to reach places.

Wheel and Axle
A wheel and axle has 2 parts to it. The wheel, and the axle! The axle is a rod that goes through the wheel. This lets the wheel turn.

A wheel and axle helps to move objects. The faster the axle is turned, the faster the wheel spins.

Maintenance of Machines

1. Greasing the moving parts of the machine regularly
2. Regular removal of dust and dirt from a machine is necessary to ensure good performance of the machine
3. Regular checking and changing of the engine oil of our machine is an important practice recommended for all users of machines
4. When an engine is not in use, we must check and warm it up to prevent rustling
5. When any machine is faulty, and the fault detected, they should immediately be corrected.

Assessment

1. Briefly explain the following; Mechanical Advantage, Velocity Ratio and Efficiency
2. A pulley system lifts a load 7m when the rope is pulled 14m by two people. What is the velocity ratio of the pulley system?

Metabolism In The Human Body

Basic Science, JSS 3, First Term, Week 9

Topic: Metabolism in the Human Body

Introduction

Metabolism is described has the chemical reaction in the body. Food substances are taken into the mouth. In the mouth, the food materials are chewed with the teeth, mixed with the saliva and rolled down the oesophagus into the stomach. The digested food diffuses into the bloodstream through the villus on the walls of the small intestine. The absorbed food circulates to various parts of the body through the bloodstream for metabolic processes. The unabsorbed food materials, however, go out of the body from the large intestine through the anus.

Digestion of Food

Digestion is the process by which complex food materials are broken down into smaller particles, with the aid of enzymes and juice produced by specialized cells and glands so that the body can absorb them. Digestion of food starts from the mouth.

All the organs that food passes through, including those that secrete substances that act on it, such as gall bladder, pancreas, salivary gland, etc., make up the digestive system. Digestive system is also known as alimentary canal. The alimentary canal has five parts through which food pass through. These include:

1. Mouth
2. Gullets (Oesophagus)
3. Stomach
4. Small Intestine
5. Large Intestine

Digestion Process

Digestion process begins with ingestion. Ingestion is the act of taking food into the alimentary canal. The food is sent to the mouth and the mouth chewed it into bits with the teeth and acted upon by the saliva that converts starch to maltose. This change is possible due to an enzyme called ptyalin in the saliva which acts on the starch. Enzymes are chemical substances produced in the body by specialized cells. They speed up digestion of food.

The food from the mouth passes through the oesophagus into the stomach where substances like gastric juice (which contains rennin and pepsin) produced in the stomach act on it. They act on protein, converting it to polypeptides in the case of pepsin, while rennin coagulates milk protein. Hydrochloric acid in the gastric juice neutralizes the alkali in food from the mouth. The food is churned in the stomach and passed into the small intestine. The small intestine consists of three parts—the duodenum (the first part), jejunum and the ileum. When the food enters into the duodenum, the gall bladder produces bile which breaks down fats and oil (emulsifies) into smaller molecules. The food also passes into the second and third parts of the small intestine where other enzymes act on it.

Absorption of Food in the Body

Absorption of food is the process whereby digested food particles diffuse into the bloodstream, which circulates them to where they are required for metabolic activities. Absorption of food takes place in the villi of the small intestine.

The digested food is absorbed into the bloodstream because it can pass easily through the walls of the small intestine through structures called the villi (singular: villus). The villus is a finger-like structure that contains a structure called the lacteal which transports fatty acids and glycerol. There are also blood vessels which transport digested proteins and carbohydrates through the capillaries.

The end products of digestion namely glucose, fatty acid and glycerol and amino acid are the substances that the body can readily use because they can pass through the small intestine directly into the bloodstream and taken to the liver. Energy from the absorbed food helps the muscles to carry out their activities as found in heartbeats, respiration, excretion, etc.

Forms in which Excess Foods are Stored

Most times, the foods we eat are in excess and so must be stored in the tissues to be used later. The ability of the body to store excess absorbed food substances that are not for immediate use is known as food storage. Of the six classes of food (i.e. carbohydrates, proteins, fats and oils, minerals, vitamins and water), only two are converted and stored in the body for use when needed. They are carbohydrates, fats and oils.

1. Carbohydrates: These are energy – giving foods. Examples include cereals, yam, potatoes, cassava, etc. These are called starchy foods which are digested into glucose. Excess glucose is converted by insulin and stored in the liver as glycogen. Some others are oxidized to carbon (IV) oxide and water which are used up by the body.
2. Fats and Oils: These are oily food substances, they are also called lipids. Fats and oils provide warmth to the system, and are also called energy – giving foods. Fats and oils are digested to glycerol and fatty acids. Excess fat is stored under the skin, around the abdomen, thigh and muscles.
3. Proteins: are not stored in the body. Blood from the small intestine only contains amino acids needed by the body at a particular time. Excess amino acids are deaminated in the liver. This is the removal of the nitrogen – containing amino group from the amino acids. The amino group is then converted into urea which is excreted by the kidney as urine.

Places of Storage

Starch in the blood is in the form of glucose and is converted by insulin and stored in the liver as glycogen. Excess fat is stored under the skin, around the abdomen, cheek, hips/waist, thigh, muscles, etc. Proteins when in excess, are not stored in the body but are immediately excreted in the form of urea by the kidney.

Problems Associated with Food Storage

• Excess glucose is stored as glycogen in the liver by the insulin. In the absence of insulin, excess glucose or sugar is found in the bloodstream. This process causes diabetes.
• Excess protein is deaminated by the liver. In any case of malfunctioning of the liver, the presence of proteins in the bloodstream causes hepatitis.
• Excess fat is stored under the skin and gives energy. The accumulation of excess fat in the skin leads to obesity and other heart diseases.

Assessment

State the forms in which excess foods are stored in the body

Sense Organs

Basic Science, JSS 3, First Term, Week 10

Topic: Sense Organs

Introduction

There are five sense organs in the mammalian body, namely: the eyes, the nose, the tongue, the ears and the skin. They are very sensitive to external and internal stimuli.

The Eye

This is the organ for seeing (sight). With our eyes, we can see things in their varying colours, shapes, sizes, etc. We have two eyes (a pair of eyes) that enable us to have a wide vision. This is called binocular vision (bi means double).

Parts of the Eye and functions

• Sclera: tough outer white layer of the wall of the eye.
• Cornea: transparent ‘window’ of the eye, focusing of light on the retina.
• Iris: the coloured sheet of muscle, controls the pupil size so controls entry of light.
• Pupil: a hole in the iris letting light into the back of the eye.
• Ciliary Body: a ring of muscle controlling the shape of the lens.
• Suspensory Ligaments: transfer the pull of the ciliary body to the lens.
• Lens: accommodation — the fine adjustment to the focusing of light onto the retina.
• Retina: light sensitive layer of rods and cones converting light into nerve impulses.
• Fovea or Yellow Spot: a tiny area of densely packed cones for detailed and coloured vision.
• Choroid: a black-pigmented layer preventing internal reflection of light.
• Blind Spot: exit point of the optic nerve cutting through the retina so no rods or cones here.
• Optic Nerve: carries the impulses from the rods and cones to the visual centre of the brain.
• Aqueous Humour: a clear liquid in front of the lens maintaining the shape of the cornea.
• Vitreous Humour: a clear jelly offering support and shape to the back of the eye.

Eye Defects and Correction

Short Sight (myopia): can view close object clearly but distant objects are out of focus. It is caused as a result of eyeball being too long or the focusing elements of the eye are too strong.

• Correction: use a concave (divergent) lens to widen the angle over which the light rays have to be refracted.

Long Sight (hypermetropia): can view distant objects clearly but close objects are out of focus. It is caused as a result of eyeball being too short or the focusing elements of the eye are too weak.

• Correction: use a convex (convergent) lens to reduce the angle over which the light rays have to be refracted.

Presbyopia: This eye defect id the loss with age of elasticity of the lens and ciliary muscle.

• Correction: use of bi-focal lenses (a combination of convex and concave lenses).

Other eye problems people can suffer from are:

Colour blindness, conjunctivitis, cataract, night blindness, muscular degeneration, glaucoma, etc.

Care of the Eyes

1. Bath with salt solution
2. Use a clean handkerchief for cleaning the eyes.
3. Consult a medical doctor in case of suspected infection
4. Use antibiotic eye drops e.g. chloramphenicol and visine in case it is inflammed (or turns reddish).

The Nose

We perceive smell and breathe through our nose. The nose has two openings called the nostrils. It is through these nostrils that we breathe air in and out. The nostrils are always wet (moist). The part of the brain that aids us in smelling is the olfactory lobe. The nasal nerves carry the messages of smell to the part of the brain (i.e. olfactory lobe) where the message is interpreted and sent back for response.

Care of the Nose

1. Do not pick your nostrils with a sharp object.
2. Do not hit anyone on the nose.
3. Always visit a doctor when you have a problem with your nose.
4. Clean your nostrils with soft tissue paper.

The Tongue

The tongue is our sense organ for taste.

We identify food as sweet, sour, salty, bitter, pungent or hot, and a flat or tasteless.

Along the sides of the tongue are the taste buds.  The taste buds have nerve endings that bring a message of the taste to the brain.

There are four areas of taste in the tongue.

The taste buds at the tip of the tongue taste sweet foods.

Those at the side taste sour and salty foods.

At the base are the taste buds which taste bitter foods

Care of the Tongue

1. Brush regularly
2. Use blunt plastic materials to scrape the surface of the tongue once in a while.
3. Rinse with salt water solution.

The Ear

The ear is an organ of hearing and also helps in maintaining balance. Each person has two ears. The ear has three major parts namely: the outer part, the middle part and the inner part.

With our ears, sounds are heard and the direction from where the sounds are coming from is also known. Sound from the environment reaches the outer ear as vibration in the air. These vibrations are carried through the external auditory meatus to the eardrum which is the opening of the outer ear. The eardrum vibrates and passes the vibrations to the ear bones called the ossicles, which are in the middle ear. The ossicles also vibrate and transmit these vibrations to the oval window. The vibration of the oval window stimulates the sensory cells of the walls of the cochlea where the nerve endings are found and the nerve endings now pick the vibration (message) to the brain for interpretation and are sent back for response through the same nerves. The nerves ending responsible for this are called auditory nerves. Once the interpretation is made, we hear the sound and also detect the direction of the sound.

Care of the Ear

1. Do not pick your ears with stick or any sharp objects, for this might puncture the eardrum.
2. The ear, the nose and the throat are linked together, so if you have catarrh, do not blow too hard on the nose or else fluid will enter the middle ear.
3. In case of any problem, consult your doctor.
4. Cotton buds should be used to remove excess wax from the ear.

The Skin

The skin is the organ of touch. Stimuli like heat, pain, cold, etc., can be felt on the skin.

Diseases of the Skin

Disease of the skin is called dermatitis, caused improper care. Such diseases as acne (pimples), eczema, dandruff, etc., affect the skin.

Care of the Skin

1. We should wash our bodies at least twice daily with soap and water to remove the accumulated dirts, oily secretion, cream, powder and bacteria. This helps to reduce or prevent body odour.
2. We should apply moisturizing cream on our bodies.
3. Our hair should be properly washed to prevent lice infestation.
4. We should expose the skin to adequate sunlight and fresh air as this enables the skin to produce Vitamin D.
5. We should exercise our bodies regularly.

Nervous System

The combination of all the nerves in the body that are concerned with the communication of feelings or sensation in living organisms makes up the nervous system.

The nerves can pick messages from either inside or outside the body, and when we respond to stimuli, a message is sent to the brain via other nerves which connect the receiving nerves with the brain.

There are two main parts of the nervous systems, which are:

• The central nervous system (CNS)
• The peripheral nervous system (PNS)

Centre Nervous System (CNS)

The brain and the spinal cord make up the central nervous system. The brain and the spinal cord help other nerves like the peripheral nerves and sense organs make responses possible.

The Brain

The human brain forms about 2% of the body mass. It is made up of structures called neurons. The brain is also called the control centre of the body because stimuli received by the sensory neurones are first taken to the brain or spinal cord, for interpretation before responses are sent to the outside through the motor neurones.

There are three types of neurones

1. Sensory neurones: these are nerves that receive the stimuli from the outside and pass the information to the spinal cord and the brain.
2. Motor neurones: when the brain or spinal cord receives the stimulus and interprets the information, the motor neurone collects the interpreted information for appropriate action in the body.
3. Intermediate/Association neurones: this connects the sensory neurones and motor neurones.

Spinal Cord

The spinal cord start from the part of the brain called medulla oblongata. It is found in the neural canals of the vertebral column. The neural canal also contains a spinal fluid known as cerebrospinal fluid. It is to the spinal cord that all the nerves are connected. The outer part of the spinal cord is called white matter while the inner part is called grey matter. It consists of the cell bodies (soma) and dendrites.

When the sensory neurones collect information from the outside, it pass it to the spinal cord then the spinal cord takes the information to the brain. After the interpretation by the brain, the information is taken back to the spinal cord to the outside through the motor neurones.

Peripheral Nervous System (PNS)

The nerves (axon, synapses, denrons and dentrites) make up the peripheral nervous system. These nerves form the sensory and motor neurones that send and collect impulses from the brain through the spinal cord. Peripheral nervous system is divided into two parts namely:

1. Somatic nervous system: these are nerves that are connected to the skeletal muscle system.
2. Autonomic nervous system: these are nerves connected to glands for metabolic processes.

Simple Reflex Action

Reflex actions are the action that cannot be control. Reflex action is therefore defined as an involuntary action. They are automatic actions that are very important for our survival. They protect us from harm and sudden danger because they act fast without our knowledge. For instance, when we step on a hot coal, we remove our legs immediately without prior preparation. Other examples include blinking of the eye, removing our hand from fire, sneezing out dust from our nose, coughing, beating of the heart, swallowing, salivation, vomiting, etc.

A simple reflex arc

The path through which impulses pass in a reflex action is called a reflex arc.

Voluntary actions are actions that can be controlled, for example, thirst, hunger, driving, eating, etc.

Assessment

• State the parts of the Eye and its functions
• Briefly explain the Nervous System

Resources From Living Things

Basic Science, JSS 3, Second Term, Week 1

Topic: Reproductive Health

Meaning of Reproductive Health

Reproductive health is the ability of people to have a satisfying and safe sex life and the capability to reproduce as well as the freedom to decide if, when and how often to do so.

Significance of Reproductive Health

Reproductive health is significant because it promotes good sexual health which enhances life and personal relations. It is also a prerequisite for social, economic and human development i.e. human energy and creativity is the driving force of development and this cannot be generated by a sick person. It sets the stage for health beyond the reproductive years for both men and women. Similarly, the health of a newborn is largely a function of the mother’s health, and nutritional status and her access to good health care.  Furthermore, reproductive health takes care of reproductive health problems at various stages in life, thereby preventing health problems at later stages in life. It contributes enormously to physical and psychosocial comfort and closeness. Reproductive health creates awareness on the dangers associated with disease, abuse, exploitation, unwanted pregnancy, etc.

Care and Protection of the Reproductive System

This is done through:

1. Circumcision of the male at childbirth reducing the effect of micro-organisms on the fore skin of the penis.
2. Regular bathing of the individual and drying of the reproductive organs.
3. Shaving of the pubic hair to avoid the growth of bacteria and fungi.
4. Ensuring thorough cleanliness of the toilet system to avoid contracting diseases, such as candidacies.
5. Washing of undies (pants) regularly.
6. Using sanitary pads by females during menstruation to avoid getting stained and infections.
7. Using tissue paper to clean up after urinating.

Sexually Transmitted Infections (STIs)

These are highly infectious diseases that are spread by sexual contact. They are referred to as venereal diseases (VD). These diseases are caused by bacteria and can survive in human body.

The two most common STIs are syphilis and gonorrhea. Other examples include, HIV/AIDS, genital herpes, etc.

Syphilis

This is caused by a spirochete bacterium called Treponema pallidum. The pathogen enters the body through a break in the skin or mucous membrane. The bacteria may attack any kind of body tissue.

This disease is highly contagious. In its early stages, the symptoms appear about 10-25 days after sexual contact with an infected person. The first sign is usually a large but painless ulcer which often appears on the penis or vulva. Other symptoms include nervousness, fever, anaemia, loss of weight and pain in the bones and joints. In the final stages, syphilis may attack the brain, spinal cord and valves of the heart, resulting in paralysis, insanity, blindness, etc.

Treatment

In the early stages, the disease can be cured by a four –day treatment with penicillin injection. Penicillin administered to a pregnant woman will also kill any spirochetes in her foetus. People allergic to penicillin can be given tetracycline or other drugs.

Gonorrhoea

This is caused by a bacterium called Neissueria gonorrhoeae and sometimes called gonococcus. There is a white discharge from the urinary tract and a burning sensation during urination in an infected person. The symptoms may be noted 3-5 days in the males. The female may show no symptoms at all. This leads to sterility, blindness in children, etc.

Treatment

A single dose of penicillin injection can cure gonorrhea if it is diagnosed at an early stage.

HIV/AIDS

• HIV- Human Immunodeficiency Virus
• AIDS – Acquired Immune Deficiency Syndrome

This disease is caused by a virus called Human Immunodeficiency Virus (HIV). An infected person with HIV has no symptoms of the disease for some years and can infect others without realizing that they are infected.

HIV can be transmitted sexually through intercourse with an infected person, from infected mother to the child during pregnancy or as a result of breast feeding, during transfusion of infected blood, using unsterilized sharp instruments, etc. however, HIV cannot be transmitted through handshakes, insect bites, water or food.

HIV infects special cells in the immune system called the lymphocytes and monocytes. It eventually destroys these cells and this leaves the individual susceptible to other diseases. This leads to vulnerability to opportunistic infections like tuberculosis, pneumonia, meningitis and possible death.

Coping Skills for Preserving Reproductive Health

1. The coping skill for preserving reproductive health are:
2. Educational empowerment: This provides girls and women information they need which affects their status as well as the control they have over their health and fertility.
3. Multi-sectoral action: Reproductive health encompasses more than biomedical aspects and goes beyond the health sector. Reproductive ill health equally lies in poverty, gender forms of inequality and social injustice, etc. To this end, different sectors can come together to promote reproductive health.
4. Prevention of reproductive tract infections (RTIs), including STIs and HIV/AIDS through preventive counseling. Condom distribution as part of primary health care.
5. Discouragement of harmful practices, such as female genital mutilation.
6. Compulsory sex education in the curriculum.
7. Abortion counseling and family planning.
8. Eating balanced diet.

Assessment

Briefly explain Sexually Transmitted Infections (STIs) you know

Soil

Basic Science, JSS 3, Second Term, Week 4

Topic:Soil

Introduction

Soil is the upper layer of the earth on which  we build houses, plant food crops, etc. All soils are mixtures of different sizes of particles. soil contains mineral salts for plant growth and some animals live in the soil.

Types of Soil

There are three types of soil. These are:

• Sandy soil,
• Loamy soil and
• Clayey soil.

Each soil type has its characteristic properties.

Composition of Types of Soil

• Sandy soils contain a high proportion of large particles (sand)
• Clayey soil contains a high proportion of small particles (clay and silt).
• Loamy soils contain nearly equal amounts of sand, clay and silt. It is the most fertile soil for agricultural purposes.

Characteristics Properties of Sandy Soil, Loamy Soil and Clayey Soil

Properties	Sandy Soil	Loamy Soil	Clayey Soil
Texture	Particles are not closely packed (loose)	Particles are closely moderately packed	Particles are packed together
Air Content	High	Moderate	Low
Porosity	High	Moderate	Poor, waterlogged
Water Content	Low	Moderate	High
Humus Content for Plant	Very little	Moderate	Variable
Provision of Support for Plants	Poor	Very good	Only to a small extent
Soil Particles	About 80% sand, 20% clay and silt	50% sand, 50% clay and silt	Sand is less, 40% clay and still about 60%.

Uses of Soil

Soil is used for:

• Agricultural purposes in planting of trees, crops, fish farming, etc.
• Building construction in making cement blocks, bricks, concrete works, etc.
• Road construction, bridges, drainage systems, taming of roads, etc.
• Pottery, decoration-marble
• Making brick oven

Importance of Soil to Plants and Animals

• To anchor plants
• As sources of plant nutrients
• Pathway for drainage
• For agricultural purposes
• For building, moulding, decorating, pottery, road construction, etc.
• As a source of food for some animals e.g. earthworms.
• As living places (habitat) for other animals, e.g. crickets, rats, snakes, ants, termites, etc.

Assessment

• State the uses of soil
• List the importance of soil to plants and animals

Ethical Issues In Science And Development

Basic Science JSS 3 Third Term

Week 4

Topic: Ethical Issues in Science and Development

Introduction

Over the years science has developed many processes and products which have conferred on the subject the formidable stature it has at the present time. Science could be used productively, such as in the production of food, curing of diseases, earning income for nations and individuals, gainful employment, etc. Science could be used destructively, such as in atomic bomb production, poisons, nuclear war, production of weapons of war and mass destruction, abortions, etc. The view of science, even in the circumstances given above as either productive or destructive, depends on which side one is considering. It should be emphasized here that when a scientist invents or discovers a thing, he/she does not do it with the intention of causing harm or fear. He does it to reveal or document what is possible or what has been happening.

Meaning of Right and Wrong Application of Science

It is sometimes very difficult to classify an application of science as right or wrong. For example, can we say it is right or wrong for women to abort unwanted pregnancies which might have occurred as a result of rape?

• The right application of science from a moral perspective is when the application is used to engender the development of society, such as provision of shelter, improvement of living conditions, improving life expectancy, fighting diseases, producing gadgets that can generate income and employment for the nation and its citizens.
• Wrong use would include any use that will lead to dehumanizing individuals or groups or cause death and suffering. Any use that does not recognize the sacredness of life is a wrong use.

Implications

• Some applications of science are harmful to individuals and even to society. Such applications ought to be controlled. For example, uncontrolled use of drugs leads to drug abuse. This may ruin the individual drug user and may lead to committing serious crimes in society.
• Children may learn new things and negative vocabulary from watching films. However, watching late night films can lead to children being corrupt or commit themselves to premature and unsafe sexual practices.

Adverse Effects on the Country

Wrong application of science can lead a country to undue loss of revenue, especially when lots of citizens spend their resources to buy foreign films and gamble on the internet. Such practices may also result in increasing number of maladjusted citizens.

Assessment

Give the Right and wrong application of science

FAMILY LIFE EDUCATION (Teenage Pregnancy)

Basic Science JSS3 Third Term

Week 1
Topic: Family Life Education

Contents:

• Implication of Teenage Pregnancy
• Myths and facts about Pregnancy

Teenage Pregnancy

This is  an unintended pregnancy during adolescence and it occurs in females under the age 20. Teen pregnancies carry extra health risks to both the mother and the baby. Pregnant teenagers face many of the same pregnancy related issues as other women. There are, however, additional concerns for those under 15 of age as they are less likely to be physically developed enough to sustain a healthy pregnancy or to give birth. It is common that at this age, the girl has not completed her education and is completely dependent upon her parents thus unable to provide for the unborn child.

Implication of Teenage Pregnancy

• The children are:
  1. Less likely to receive timely and consistent prenatal care.
  2. More likely to be born prematurely, to have low birth weight and more serious medical and developmental problems.
  3. More likely to live in poverty.
  4. More likely to have lower academic performance, worse behavioural outcomes and become school dropouts.
  5. More likely to require government assistance and taxpayer-funded programs.
  6. More likely to be victims of abuse.
  7. More likely to be committed to a juvenile detention facility or prison.
  8. More likely to continue the cycle of teen pregnancy by engaging in sex at an earlier age.

The mothers are:

• More likely to have pregnancy or delivery complications.
• Less likely to get a high school diploma.
• Less likely to get a college degree.
• More likely to live in poverty.
• Less likely to be in a stable marriage or relationship.
• More likely to get government help such as welfare, housing assistance and food stamps.

Myths and Facts About Teenage Pregnancy

• Myth: Everyone is doing it.Fact: Who, exactly, is everyone? Don’t be so gullible. The reality is that less than half of all high school students have had sex – ever.
•  Myth: Girls can’t get pregnant during their period.Fact: Most girls ovulate in the middle of their cycle on about day 14 after their period starts, but some ovulate closer to or during their period. Also it is important to remember that sperm can survive in the body for up to seven days. If you ovulate within a week of having unprotected sex, there is a possibility you can still become pregnant.
• Myth: You can’t get pregnant if you have sex standing up.Fact: Yes, you can get pregnant this way whether standng or sitting. No matter what position you are in, whenever you are having vaginal sex, especially without any form of protection, you are at risk of getting pregnant. Gravity has no effect on a sperm’s ability to travel through the vagina, into the uterus, where it can potentially reach an egg. The truth is that there is no sex position where you can’t get pregnant.
• Myth: Is there an age limit? Can someone be too young to get pregnant?Fact: No. Once a woman is ovulating, she can become pregnant. This can happen even before your first period (since ovulation begins 14 days before your period).
• Myth: You’re a prude if you wait until you’re older.Fact: Prude? How about Smart. Everyone is different and everyone is unique. And, everyone has a time that is exactly right for them. Truth told, young teens who have sex say they regret it and that they wished they’d waited.
• Myth: What if the guy “pulls out” before he finishes?Fact: Once a guy is aroused, he releases pre-ejaculation fluid. That’s at least 300,000 sperm swimming upstream. And guess what? It only takes 1 sperm to fertilize an egg. 
• Myth: You can’t get pregnant the first time you have sex.

Fact: First time or Tenth time, it doesn’t really matter, your chances of becoming pregnant are the same. Even if a girl has never had her period, there is a possibility that she’s about to start her first cycle. In that case, then she has already ovulated, which means that an egg is present, and when an egg and sperm are present, pregnancy can occur.

Assessment

• State the Implications of Teenage Pregnancy

Radioactivity

Basic Science JSS3 Third Term

Week 3

Topic: Radioactivity

Introduction

Radioactivity is the disposition of certain elements to send out rays on their own. This makes the nuclei break down. It also refers to the particles which are emitted from nuclei as a result of nuclear instability. Because the nucleus experiences the intense conflict between the two stronger forces in nature, it should not be surprising that there are many nuclear isotopes which are unstable and emit some kind of radiation. The most common types of radiation are called alpha, beta and gamma radiation, but there are several other varieties of radioactive decay. The atom has a nucleus around which electrons evolve. The nucleus contains protons and neutrons. A proton has a positive electric charge while the neutron is neutral i.e. it has no charge. The electron has a given negative electric charge. When a radioactive element sends out rays, the structure of its atoms changes, in some cases the number of electrons revolving round the nucleus reduces.

Radioactive Elements

There are naturally occuring radioactive elements and artificial ones. Natural radioactive elements include radium, uranium, plutonium, thorium etc. Artificial radioactive elements are made by using neutrons and protons t bobard the normal atoms of sulphur, iodine and cobalt include sulphur-35, iodine-131 and cobalt-60. They are artificial isotopes and so are called radio-isotopes since they are radioactive elements. Both natural and artificial radioactive elements disintegrate by giving out alpha, beta and gamma rays. 

Properties of Radiation

Radiation	Alpha (α) –particles	Beta particles	Gamma (λ) rays
Nature	Helium nuclei 42H	High energy electrons	Electromagnetic waves of very short wavelength

Uses of Radioactivity

1. Treatment of Cancer – Cancer of the skin or an organ such as the breast is treated with gamma rays. Once every month or at intervals prescribed by the doctor, the part of the body affacted by the cancer is exposed to gamma rays for a short time.  This treatment is called Radiotherapy and it is continued till the affected part is healed.
2. Sterilisation of Fruit and Drinks – In the past, germs in bottld drinks and canned foods were killed by a process called pasteurisation. The bottled drink or food was warmed to a temperature that killed the germs. In some cases, chemicals were added to the canned food or drinks such as orange juice.
3. Sterilisation of syringes and medical equipment was done in the past with boiling water. It is believed that application of heat to the water in these instruments to 100 degree celcius will kill germs and bacteria. It is now easier to use gamma rays to kill bacteria in syringes and medical equipment.
4. Carbon dating is a method used to find the age of very old objects. The radiation given out in a given time interval is proportionate to the whole radiation that has been given out in the time past. This is because reduction in radiation is proportional to the age of the object.

Dangers of Radioactivity

1. Though alpha particles may not be able to penetrate into the body as they are stopped by the skin’s outer layer, they are dangerous and injurious to organs
2. The beta particles can penetrate the body where they damage and destroy cell tissue. 
3. Gamma rays are even more dangerous inside the body, they penetrate deeper into the body than the other two rays. They destroy the cells of bodies exposed to them. They also upset the natural chemical reactions of the body and this may cause death or at best injure the parts exposed to them.

Assessment

1. Radioactivity is the spontaneous ____ of the nuclei of some elements to give off radiation in the form of particles or rays
   a. integration
   b. disintegration
   c. aggregation
   d. formation
2. Which of this element is not a natural radioactive element?
   a. sulphur
   b. uranium
   c. radium
   d. thorium
3. The following are artificial radioactive elements except
   a. Sulphur-35
   b. Uranium-238
   c. Cobalt-60
   d. Iodine-131

Answers

1. B
2. A
3. B

Family Health Education (Abortion)

Basic Science JSS3 Third Term

Week 2
Topic: Abortion

Abortion

Abortion is the removal of pregnancy tissue, products of conception or the fetus and placenta (afterbirth) from the uterus. It can also be defined as the ending of pregnancy by removing a fetus or embryo before it can survive outside the uterus. An abortion may be caused purposely and is then called an induced abortion, or less frequently, “induced miscarriage”. 

Reasons for Abortion

• Failure of Contraceptives or Birth control. 
• To end an unwanted pregnancy or teenage pregnancy.
• Inability to support or care for a child.
• Pregnancy resulting from rape or incest.
• Poverty
• To prevent the birth of a child with birth defects or severe medical problems. Such defects are often unknown until routine second-trimester tests are done.
• Physical or mental conditions that endanger the woman’s health if the pregnancy is continue

Types of Abortion

Medical Abortion – Medical abortions do not involve surgery or other invasive methods but rely on medications to end pregnancy.

Surgical Abortion – All surgical abortions are medical procedures that must be done in a health care provider’s office or clinic. Aspiration is an abortion procedure that can be performed on a woman up to 16 weeks after her last period. Dilation and evacuation (D&E) is typically performed during the second trimester (between the 13th and 24th week of pregnancy.) .

Unsafe Abortion – An unsafe abortion is the termination of a pregnancy by people lacking the necessary skills, or in an environment lacking minimal medical standards, or both.

Complications of Unsafe Abortion

• Severe damage to internal organs
• A large range of infections
• Uterine perforation when the uterus is pierced by sharp objects
• Incomplete abortions, when all pregnancy tissues aren’t pulled out
• Heavy internal bleeding
• Excruciating abdominal pain
• Collapse of the circulatory system
• Abnormal vaginal bleeding

Assessment

• What are the complications of unsafe abortion
• State the reasons of abortion

Basic Electronics

BASIC TECHNOLOGY

JSS 3 – 3^rd Term

Week 3

Basic Electronics

Outline:

• Basic emission theory
• Types of emission devices

Basic Emission Theory –

If we provide energy to an electrode then the electrons in the outermost shell of the atom of the metal gain enough energy to eject from the surface of that metal or electrode. This process is called electronic emission.

The term emission means the dislodgement or displacement of electrons from a material with the intention of directing such emitted electrons to a predetermined position or object.

When electrons are displaced from the outermost layer of an atom of any material, they form free electrons and emission takes place. The continuous movement or drifting of such free electrons constitutes the flow of electric current. These free electrons also form the basis of operations of both electronic and electrical devices.

Emission theory, also called emitter theory or ballistic theory of light, obey the principle of relativity by having no preferred frame for light transmission, but say that light is emitted at speed “c” relative to its source instead of applying the invariance postulate.

History

The name most often associated with emission theory is Isaac Newton. In his corpuscular theory Newton visualized light “corpuscles” being thrown off from hot bodies at a nominal speed of c with respect to the emitting object, and obeying the usual laws of Newtonian mechanics, and we then expect light to be moving towards us with a speed that is offset by the speed of the distant emitter (c ± v).

Types of emission:

1. Thermionic Emission:

This type of emission of electrons is obtained by heating the metal surface directly or indirectly to free or liberate electrons. The metal on which effort is applied for the purpose of removing electrons is called metal electrode. In this type of emission, the electron emission is achieved by heating the metal electrode. Due to the heating of the metal, the electrons get enough energy and they ‘escape’ from the surface of the metal. An electron emitted from a hot cathode comes out with a velocity that presents difference between the kinetic energy possessed by the electron just before emission in cathode, diode, triode, pentode, CRT and many others.

Thermionic emission

In a simpler explanation about the process of thermionic emission, the electrode is heated by an electric heater just to raise the temperature a little above normal room temperature. This increases the heat or thermal energy of the surface electrons, enabling them to attain sufficient and high speed thereby causing them to escape from neighboring atoms at the surface of the electrode. The electrode is called the emitter because of the streams of electrons coming from its surface. The higher the temperature of the emitter, the greater the number of free electrons which will be released from its surface. The source of heat in the thermionic emission of electrons can be obtained either by:

1. Direct heating method
2. Indirect heating method

In the direct heating method, the metal electrode is heated by connecting electric current to the metal electrode which itself can be in the form of a wire.

In the indirect heating method, a separate heating element is heated and usually placed into the metal electrode called cathode. It is coated with an electron emissive substance (a substance that can emit electrons). The cathode is heated up by the heat transferred from the heating element. The current used for heating the cathode or emitter may be direct current (d.c.) or alternate current (a.c.). This type of emission is referred to as primary emission

2. Photoelectric emission

Photoelectric emission is another method of liberating electrons from a material for a useful purpose.

Photoelectric emission occurs when light falls on a metal surface causing electrons to be emitted. Photoelectric emission is the liberation of electrically charged particles from matter when light falls on it. It employs light energy from through dissimilar material =s for the liberation of electrons.

A photoelectric cell works on the principle of electric charges produced when a cell containing photosensitive materials is exposed to light rays. A typical photocell is in the form of a metallic sandwich shaped like a disc. It consists of three layers of different materials which allow light to pass through it.

Photoelectric emission

When light is focused on the Selenium which is situated in the middle of the sandwich it allows light through the translucent film and an electric charge is created between the film and the iron layer. An ammeter connected across these layers will deflect thereby indicating the amount of electric charge generated. This type of photocell is used by photographers to indicate the quantity of light allowed in their studios. The photoelectric cell is employed in operating burglary alarms, traffic lights control and automatic doors.

3. Cold-Cathode emission

The method of liberating electrons in order to obtain free electrons is achieved either by the use of energy stored in an electric field or a magnetic field. Cold or field emission is obtained from one or two electrodes when there is a sufficient potential difference (p.d.) between the electrodes. The emission is caused by reducing the potential barrier at the surface of the emitter.

Cold-cathode ray emission

4. Secondary emission

The principles employed in the secondary emission to free electrons is the use of kinetic energy i.e. electric charges sufficient enough to bombard the surface of the metal electrode. The free electrons obtained can be used for controlling electronic circuits.

Assessment

Briefly explain the types of Emission