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Combustion

Thu, 13 Feb 2025 19:54:23 +0000

In 1769, Nicolas-Joseph Cugnot built the first self-propelled vehicle which was powered by steam made by heating water from burning wood. The steam was then passed to engine to drive the wheels. However it was too slow and heavy to be useful.

Then in 1861, Thomas Rickett’s steam carriage used coal as the fuel.

The Benz Patent-Motorwagen of 1886 was the first modern car. Its engine ran on petrol. The fuel was burned inside the engine. This type of engine is known as the internal combustion engine that is used in cars till date.

Several car manufacturers are developing hydrogen fueled cars. These cause less pollution than petrol and diesel vehicles.

Most hydrogen-powered vehicles use fuel cells, in which energy is released from hydrogen in a carefully controlled manner and reacts with oxygen.

We can model the reaction in a fuel cell using a word equation: hydrogen + oxygen → water

In the hydrogen fuel cell in the bus below, hydrogen fuel releases energy that is transferred to electricity to make the bus move.

Hydrogen gas is flammable. In the 1930s, airships were built to carry passengers long distances. Many were filled with hydrogen, which made them float in air. In May 1937, the Hindenburg airship burst into flames. The flames quickly spread as the hydrogen reacted with oxygen in the air. The accident killed 35 of the 97 people on board.

Fuels

A fuel is a chemical or nuclear substance from which stored energy can be transferred usefully (usually in the form of heat and light.) Examples of fuels:

Firewood
Hydrogen
Biofuel
Fossil fuels
Nuclear fuels

Food & Digestion

Tue, 04 Feb 2025 13:06:03 +0000

Food contains nutrients (raw materials) needed for energy, growth and repair, and for health. The nutrients are: carbohydrates, fats, proteins, vitamins and minerals.

Nutrition information labels can tell us how much of each nutrient can be eaten in a day (reference intake) and how much of that nutrient is in the particular food. This helps you know how much of the food you need to eat.

Nutrition labels give you the amount of energy in food (in kilo Joules and kilo Calories). 1 kilocalorie = 4 kiloJoules. Energy requirements change with age, type of activity and gender.

Uses of Nutrients

Water – transports the nutrients in the body, acts as a lubricant, fills up cells so that they hold their shape and cools us down when we sweat.
Protein– help in making new cells for growth and repair. Found in meat, fish eggs, cheese, beans and milk.
Carbohydrates– for energy. Found in starchy foods like bread and potatoes and sugary foods containing glucose.
Lipids (fats and oils)– are a source of energy and provide insulation. Found in dairy products and oily foods.
Vitamins and minerals– for overall body health and protection from disease.
Fibre - is not a nutrient but needed as roughage – Fibre contains plant cell walls which cannot be digested but helps food move through the intestine to prevent constipation.

Food Tests

To test for the presence of water in a particular food, blue cobalt chloride paper is used. It turns pink, in the presence of water.
To test for the presence of the carbohydrate starch in a particular food, iodine is used. Brown iodine turns blue-black in the presence of starch.
To test for the presence of fats in a particular food, add ethanol and then the same amount of water. A white emulsion will be formed if fats are present.
To test for the presence of protein in a particular food, blue Biuret solution turns purple in the presence of protein.

Balanced Diet

A balanced diet contains the right amount of a wide variety of foods that can provide all nutrients + fibre for growth and repair, health and energy.

Malnutrition

Too much or too little of a nutrient in your diet can make you malnourished. Too much of carbohydrates and fats can cause obesity which leads to heart disease. The extra fat can clog arteries and cause heart attack. Higher pressure on artery walls results in high blood pressure which further damages the heart and bursts blood vessels and damages kidneys.

Deficiency diseases are caused by too little of a certain nutrient. The tables below show the vitamin and mineral deficiency diseases.

Kwashiorkor is a deficiency disease caused by lack of protein in ones diet. A pot belly is the symptom of this disease as muscles that hold the abdomen get weak.
Lack of carbohydrates, fats and proteins cause starvation which causes anorexia (getting thinner and thinner)
Too much of carbohydrates and fats with no exercise causes obesity

The Digestive System

Enzymes

Enzymes are biological catalysts that speed up digestion and don’t get used up in the process and remain unchanged.

The mouth contains the enzyme salivary amylase to digest starch.

The stomach contains pepsin that functions in hydrochloric acid to digest protein.

The duodenum contains pancreatic amylase, lipase and trypsin.

The small intestine contains lactase, maltase, sucrase-isomaltase, peptidase

GUT BACTERIA

We have a mix of good and bad bacteria in our gut. Helicobacter Pylori causes ulcers, while Lactobacilli may ward off stress and anxiety. Your diet can affect which bacteria grow and reproduce more than another. Taking probiotics containing good bacteria such as yoghurt can help keep your gut healthy. Prebiotics are fibers which our body cannot digest but good bacteria feed on. Taken together, prebiotics and probiotics can turn into a healthier, happier gut.

INFLUENCE OF GUT BACTERIA ON OUR BRAIN AND BODY Gut bacteria influence our overall body health. Imbalances in the amounts of various bacteria causes:

Depression & anxiety
Irritable bowel syndrome – symptoms: cramping, abdominal pain, bloating, gas, and diarrhea or constipation, or both.
Colon cancer
Changes in brain function
Obesity & Diabetes

ABSORPTION

After enzymes break up the large insoluble molecules into smaller soluble ones, the small molecules can be absorbed by the small intestine.

Digestion ends in the small intestine and the products of digestion (glucose, amino acids, glycerol and fatty acids) that are soluble molecules get absorbed into the blood inside the villi of the small intestine.

Diffusion in small intestine - Particles tend to evenly spread out by diffusion from a high to low concentration. After a meal, there are more digested nutrient molecules inside small intestine than in the blood. This causes the overall movement of the nutrient molecules into the blood by diffusion to achieve a balance of these nutrients in small intestine and in the blood.

Adaptations of small intestine for absorption - The wall of the small intestine is folded with many villi that provide a large surface area for maximum absorption of nutrients into blood. The wall of each villus is only one cell thick so nutrients do not have to diffuse far to get into the blood. This speeds up the absorption.

Visking tubing model of small intestine:

Inside of tubing represents inside of small intestine.

Outside of tubing represents the blood.

Sound

Sat, 21 Sep 2024 13:29:43 +0000

•Sound is a vibration we can hear.

•A vibrating object makes sound

•Sound travels through air. It travels more quickly through solids than liquids or gases

•Speed of sound in air = 330m/s

•Sound needs particles to travel through them

•Sound cannot travel in a vacuum where there are no particles.

•Sound waves can pass through materials.

A wave is a vibration or disturbance in space.

Sound waves are longitudinal which means the direction of vibration is parallel to the direction of motion of the wave. Particles in a sound wave experience a back and forth movement.

The sound wave contains high pressure areas where particles get closer called compressions and low pressure areas where particles are further away called rarefactions.

Regions of compressions make the crest of the wave while areas of rarefactions make the trough of the wave. The distance between every two crests or every two troughs is called the wavelength.

Amplitude is the distance that particles move from rest when a sound wave passes through them. The louder the sound the greater the amplitude. The quieter the sound, the shorter the amplitude.

The shorter the wavelength, the higher the pitch of the sound and the higher the frequency.

The longer the wavelength, the lower the pitch of the sound and the lower the frequency.

•Frequency is the number of vibrations per second

•Frequency is measured in Hertz (Hz)

•1 Hz = 1 Vibration per second = 1 back and forth movement of particles in one second.

Humans can hear frequencies between 20Hz to 20,000Hz.

Sounds below 20Hz are called infrasounds

Atoms, Elements & Compounds

Tue, 12 Dec 2023 16:11:24 +0000

Elements are the building blocks of all matter. The Periodic Table of Elements show all the 118 elements that make up all matter on Earth. Each element is made up of its own special type of atom.

ATOM

•It is the fundamental particle that makes up all matter.

•It is the smallest particle of an element that has all the properties of that element.

•Can be represented as a tiny ball…

……but it is actually made up of electrons whizzing around a central nucleus containing protons and neutrons.

ELEMENTS

– are made up of a certain type of atom. A pure substance contains only one type of atom… (an element is considered to be a pure substance)

COMPOUND

– made up of different elements (different kind of atoms joined together)
To make a compound, the atoms of the different elements must chemically join together. If they don’t join, then it is a mixture of elements.
Other compounds include:

Molecule –

a general word to describe many atoms joined together

MIXTURE

– having many molecules of compounds and/or molecules of elements mixed together.

A pure substance contains only one type of molecule of an element or one type of molecule of a compound…

AIR IS A MIXTURE

The air we breathe is not pure. It is made up of a mixture of gases including nitrogen, oxygen, argon, water vapour and carbon dioxide.

Metals vs Non metals

Metals are found on the left hand side of the periodic table while non-metals are found on the right hand side of the periodic table.

Metals are:

shiny
sonorous,
conductors of heat and electricity
malleable and ductile
mainly solids at room temperature because they have high melting and boiling points

Non- metals are:

dull
brittle
insulators of heat and electricity
are mainly gases and liquids at room temperature because they have low melting and boiling points.

Metal ores – where metals are extracted from

•Ores are naturally occurring rocks that contain metals or metal compounds in sufficient amounts to make it worthwhile extracting them.

•Most of the compounds found on Earth including metal ores were formed millions of years ago.

•Metal ores are rocks containing a metal which can be used as a source of the metal.

How do elements form compounds?

•Two elements can be combined by heating them.

•Energy is often given out when elements react to form compounds.

E.g: Iron and Sulphur can be joined together to form a compound called Iron Sulphide.

iron + sulphur → iron sulphide

Bonds are formed between iron and sulphur atoms to make them bonded together in iron sulphide.

A chemical reaction takes place when compounds are formed from their elements or if a large compound breaks into smaller elements or compounds.

Thermal decomposition - When compounds form elements (heat can split a compound into its elements)

Some compounds can thermally decompose to form other compounds:

CHEMICAL REACTION signs

•Colour change

•Smell

•Bubbling (Effervescence) because a gas is given off

•Solid (precipitate) forming

•Heat given off

Ecosystems & Variation

Sun, 10 Dec 2023 09:39:42 +0000

Levels of organisation:

Individual → Population → Community → Ecosystem → Biome → Biosphere

•An ecosystem is a community of living organisms (plants, animals and microbes) in relation with the non-living components of their environment (things like air, water and mineral soil), interacting as a system.

A habitat is the natural home of an animal, plant, or other organism. A good habitat meets all the environmental conditions an organism needs to survive. … An ecosystem is made up of living organisms and nonliving components such as air, water and mineral soil.

•A community is an association of populations of two or more different species occupying the same geographical area and in a particular time.

•A Population is a group of individuals of the same species inhabiting the same area.

•A species contains closely related organisms that are very similar to each other and are usually capable of interbreeding and producing fertile offspring.

There is greater variation between different species than within the species itself.

•Hybrids are infertile offspring between two different species.

Animals and plants must be adapted to their habitats if they are to survive in the ecosystem

ADAPTATIONS- features which help organisms survive in a habitat

The adaptations of an organism can be inherited.
INHERITED VARIATION – variation due to features passed down by parents to offspring.

•Different species have the most inherited variation compared to inherited variation between same species.

•Members of the same species have inherited variation because all gametes contain slightly different instructions for features. A different sperm cell and egg cell are used to produce each offspring and so each inherits a slightly different mix of features.

•However, identical twins are an exception since they both develop from the same fertilized egg cell.

ENVIRONMENTAL VARIATION – variation caused by environmental factors such as sunlight, temperature, oxygen, pH, moisture and availability of nutrients.

All organisms show inherited variation and environmental variation

How does the environment affect organisms?

•Environmental factors affect organisms. Some organisms inherit features that allow the organism to change when environmental factors change.

•Nocturnal animals are active only at night when there is no sunlight and are adapted to do so by inheriting powerful hearing and eyesight and being able to move silently to catch nocturnal prey.

•Organisms adapted to changes in tides during the day e.g seashore organisms that have tentacles that can be pulled inwards when the tide is out to stop the organisms from drying out.

•Deciduous trees can lose their leaves during the winter when there is not enough sunlight for photosynthesis and their leaves also lose water when the ground is frozen.

•Evergreen tress are adapted to keep their leaves all year round since their leaves are tougher and don’t lose much water.

•Poppies are plants which die in the winter but their seeds grow in spring .

•Bluebells are plants that have bulbs underground that can grow into a plant again in spring as during winter the parts of the plant above the ground die.

•Rabbits can grow longer fur during winter.

•Ptarmigans feathers can change colour with the seasons to help it camouflage better.

•Hedgehogs hibernate (i.e. become inactive in the winter when there is less availability of food.)

•Birds fly and migrate to warmer places during winter to find food.

How do organisms affect their environment?

Organisms compete for resources in their environment such as:

•Food

•Water

•Oxygen

•Space

•Shelter

•Mates

•Light

•Warmth

•Minerals

Human activities such as deforestation and competition for these resources can further reduce them and when these resources are missing populations reduce and organisms can get extinct.

Interdependence

The organisms in an ecosystem all depend on each other. They are interdependent. E.g. birds use trees for shelter and plants use animal waste (containing mineral salts) to help them grow. A food chain shows how organisms depend on each other for food.

•The arrows in a food chain show energy flow as one organism eats the other.

Populations are affected by availability of food. Organisms compete for food. Increase in prey can increase the number of predators.

Fitness - Muscles & Breathing

Mon, 13 Nov 2023 17:47:29 +0000

•Being fit can be defined as the ability of a body to cope with all the demands of its lifestyle.

•Fitness is made up of four factors: 4 S-factors:

MUSCLES & BREATHING

•Oxygen is needed by cells to respire and release energy.

•Cells get the oxygen they need from the blood. Oxygen enters the blood in your lungs. The circulatory system carries blood carrying oxygen to each body cell.

•Respiration in cells produces carbon dioxide gas which enters blood and then leaves the blood into the lungs for it to be exhaled (excreted).

The gas exchange system

•In the lungs, oxygen enters blood and carbon dioxide leaves it. One gas is exchanged for the other and this is known as gas exchange.

BREATHING

•Breathing involves muscles of the diaphragm and muscles between the ribs changing the size of the lungs.

•Muscles are made of nerve tissue and muscle tissue.

•Muscle tissue is made from muscle cells which can contract and relax.

•When you inhale, rib muscles and the diaphragm contract to increase size of the lungs for air to flow in them.

•When you exhale, rib muscles and the diaphragm relax to reduce the size of the lungs for air to flow out of them.

Muscles & Blood

•Each time your heart pumps blood it causes a pulse. The pulse rate is the number of pulse beats you can feel in a minute.

•Fitter people have lower pulse rates than unfit people when resting. Most people have pulse rates of between 60 to 100 beats per minute. Fit athletes have pulse rates below 50 beats per minute.

•The left side of the heart has much more muscle than the right. Muscle tissue in the heart contracts to push blood through the heart and into blood vessel called arteries.

•Arteries lead into tiny blood vessels called capillaries which have very thin walls made up of very thin, flat cells so that nutrients (from food) and oxygen can leave the blood and get into cells for respiration and growth. The capillary walls keep large structures such as red blood cells inside the capillary. Other substances such as oxygen, carbon dioxide, glucose (sugar), and water can pass through.

•The blood then picks up waste materials from cells as it travels through capillaries and then into veins which carry blood back to the heart.

When the heart pushes blood into the aorta, the blood’s impact on the elastic walls creates a pressure wave that continues along the arteries. This impact is the pulse.

The normal breathing rate of 12-18yr olds is 12 to 16 breaths per minutes. (One complete breath comprises one inhalation when the chest rises, followed by one exhalation when the chest falls. To measure the breathing rate, count the number of breaths for an entire minute or count for 30 seconds and multiply that number by two.)

The normal heart rate of 12-18yr olds is 60 and 100 beats per minute. With activity, the heart rate may get as high as 200 beats per minute. (When you feel your pulse, count the number of beats in 15 seconds. Multiply this number by four to calculate your beats per minute.)

The walls of capillaries are made up of very thin, flat cells. The capillary walls keep large structures such as red blood cells inside the capillary. Other substances such as oxygen, carbon dioxide, glucose (sugar), and water can pass through.

BLOOD

•The liquid part of blood is called Plasma. Plasma contains dissolved nutrients and waste which are carried by blood.

•Blood contains Red blood cells which carry oxygen. Copy FACT pg 43

Adaptation:

1.They don’t have a nucleus so the cytoplasm can pack hemoglobin which is where oxygen is carried.

2.The cells have a curved disc shape which gives them a large surface area for oxygen to quickly get in and out of them.

•Blood also contains white blood cells to fight infections and keep you healthy.

Red blood cells and white blood cells are made in the bone marrow tissue in bones.

THE SKELETON

Bones are hard, strong (to withstand pressure) and light (can be moved easily). They are living organs containing the following tissue:

•Cartilage tissue – flexible but resists stretching

•Osteoblast tissue – bone making cells called osteoblasts make compact bone and spongy bone

•Bone marrow tissue – reduces mass of bone and makes blood cells.

FUNCTIONS OF THE SKELETON

•Support -The human body’s main support is the backbone made up of smaller bones called the Vertebrae. Bones like the ribcage help support internal organ
•Protection – Bones protect internal organs e.g the skull protecting the brain from injury
Movement –

•Two bones next to each other can form a joint.

Types of Joint:

•Fixed joint – where bones meet but cannot move e.g. in the skull

•Flexible Joint – where bones can be moved by muscles. The muscles are attached to the bones by tendons. Ligaments hold the two bones together. Cartilage is a slippery tissue that can allow the two bones to slide past each other.

Flexible joints include:

Hinge joint – e.g elbows & knees

Ball and Socket joint e.g. Hips & shoulders

Muscles and Moving

The muscles and bones form the locomotor organ system which allows you to move the parts of your body. Biomechanics is the study of how muscles and bones work together.

Thicker bones are needed to support bigger muscles.

ANTAGONISTIC MUSCLES

A muscle can only pull on a bone and not push back on it. So in order to lift and lower a bone, it needs two separate muscles that are antagonistic to each other - which means if one contracts to lift the bone, the other relaxes.

E.g. To lift the lower arm bone, biceps muscles contract and the triceps muscles relax. To lower the arm bone back, the triceps contract while the biceps relax. Therefore biceps and triceps are an antagonistic muscle pair.

Other examples of antagonistic muscle pairs in the body are:

wrist flexor and wrist extensor to move the wrist bone
calf and shin muscles to move the foot
biceps femoris and quadriceps to move the lower leg.

DRUGS

A drug is a substance that affects/changes the way your body works.

Types of Drugs:

Medicinal Drugs

These types of drugs help people fight diseases and recover from injuries.

Examples include:

Paracetamol that reduces swelling
Ibuprofen which reduces pain and swelling
Decongestants to help recover from flu by helping you breathe easily e.g. Salbutamol is used to treat asthma by relaxing airway muscles and decongesting them making it easier to breathe.
Antibiotics to kill bacteria in bacterial infections
Antivirals to fight virus related infections
Antifungals to kill fungi infections

Although these drugs are useful they may have harmful side effects e.g most drugs can damage the liver whose job is to break drugs down in the body.

Recreational drugs -

Legal recreational drugs – Caffeine (stimulant), nicotine (stimulant) and alcohol(depressant).
Illegal recreational drugs – Cannabis (cause memory loss and mental illness), Ecstasy (a stimulant causing mental illness, kidney problems and even death), Cocaine (a stimulant which blocks arteries), Heroin (a depressant causing collapses veins, vomiting and severe headaches)

Substance Misuse – is the harmful use of drugs.

•Drugs can become addictive which means people feel like they can’t live without them. Addicts are people who are addicted to drugs and keep using them even though the drugs cause them harm.

•Overdoses of drugs can lead to death.

•Overuse of steroids (medicinal drugs that work like hormones) can cause drastic changes in a person’s body.

SI Units

Sat, 28 Oct 2023 08:28:37 +0000

SI units are an International System of units that are recognized and used in calculations by scientists world wide.

Fundamental SI Units

1. Length - SI Unit is meters with the symbol m.

2. Mass- SI Unit is kilograms with the symbol kg.

3. Time- SI Unit is seconds with the symbol s.

4. Electric current- SI Unit is amperes with the symbol A.

5. Temperature- SI Unit is Kelvin with the symbol K.

Derived units (from the fundamental units)

1. Area- SI Unit is derived from length x length - meters squared with the symbol m2

2. Volume- SI Unit is derived from length x length x length- meters cubed with the symbol m3.

3. Velocity- SI Unit is meters per second with the symbol m/s

4. Acceleration - SI Unit is meters per second squared with the symbol m/s2

5. Density - SI Unit is kilograms per meter cubed with the symbol kg/m3.

6. Force- SI unit is derived from mass x acceleration with the symbol N for Newtons

Pressure - SI unit is derived from force/area with the symbol Pa for Pascals.
Energy - SI unit is derived from force x area with the symbol J for Joules.
Power - SI unit is derived from energy/time with the symbol W for Watts.
Moment or Torque - SI unit is derived from force x length with the symbol Nm

Forces

Tue, 08 Aug 2023 13:58:55 +0000

•A force is a push or pull on a body.

•Force causes motion: change in speed, direction, shape or size.

•SI Unit of Force: Newton : N

Types of forces:

•Contact Force - force between objects that are touching each other. e.g friction, upthrust , reaction force

•Non Contact Forces -force between objects that are not touching each other e.g gravitational, magnetic and electrostatic forces

Friction

Friction acts to slow objects down. Friction is the force opposing motion. It produces heat.

How is friction reduced?

•By lubrication -Using a lubricant – such as oil or grease

•Making the surface smoother

•Streamlined shape to reduce air resistance or water resistance.

Air Resistance (drag force)

Air reistance is an opposing force slowing down objects moving through air.

Reduce air resistance on a body by making the body have a streamlined shape:

Water resistance

Water resistance is an opposing force slowing down objects moving through water. It can be reduced by making the object have a streamlined shape and lubricating it.

Upthrust

Upthrust is the force that makes things float. It acts opposite to weight.

Weight

Weight is the force of gravity acting on an object with mass.

Your weight is determined by your mass and the gravitational field strength of Earth.

Every 1kg of mass on Earth is pulled with a force of 10N towards the center of the Earth. The gravitational force is therefore 10N/kg. (10N per kg).

So a 50kg weight would be pulled towards Earth with a force of 500N:

1kg : 10N

50kg : (50x10)/1 = 500N

Therefore:

Weight (N) = Mass (kg) x Gravitational force per every 1kg of mass (N/kg)

The gravitational field strength on the moon is about 2N/kg so weight on the moon will be less than on Earth.

The force meter – used to measure Force (weight)

Springs are used inside force meters that are used to measure weights of certain masses.

If the meter is measuring a small weight, the spring stretches by a small amount. If the meter is measuring a large weight, it stretches by a larger amount.

Most force meters have a force limit to them so weights exceeding that limit cannot be measured using them.

Extension and Springs

•When a force / weight is applied on some materials, it can cause them to stretch or compress leading to an extension (a change in length from original length of spring)

•Springs extend when weights are placed on them. With springs, the extension is proportional to the force up to a certain point after which the spring can permanently get deformed or even snap. This was known as Hooke’s law.

Hooke’s law states: Extension of a spring is directly proportional to the force until the elastic limit (or limit of proportionality) is reached.

This means that with every increase in force applied to the spring, the extension will increase by the same amount up to a certain point after which the spring can snap or lose its elasticity.

The spring stretches by the same amount (x) as you keep increasing the amount of force (F) steadily on the spring.

So Hooke’s law: force is directly proportional to extension means: Doubling force, doubles extension; tripling the force, triples extension)

There’s a limit to the amount of force a spring can withstand. When this elastic limit is passed, the spring gets deformed and Hooke’s law no longer works which means with increase in force, the extension will not be the same.

Hooke’s law: Force is proportional to extension until elastic limit is reached.

With every 0.4N of force, the extension increases constantly by 2cm. The spring is obeying Hooke’s law.

Elastic limit/ Limit of proportionality is at 1.6N. When force added is greater than 1.6N the extension does not increase constantly.

After elastic limit the spring does not return to its original shape.

Balanced and Unbalanced Forces

Balanced forces are forces on an object that are the same size but work in opposite directions. If forces are balanced:

a stationary object stays stationary.
a moving object continues to move at the same speed and in the same direction.

If there are unbalanced forces on an object:

a stationary object will start to move.
a moving object will change its speed or direction.

Resultant Force

The resultant force is the overall force with which an object moves in the direction of the greater force.

When forces are balanced, the resultant force is zero.

Pressure, Force and Area

Pressure is the force of particles pushing on an area,

The units for Pressure are Pascals (Pa)
1Pa = 1N/m2

•For the same force; a large area gives less pressure and a small area, gives high pressure.

•For the same area, a large force gives high pressure and a small force gives low pressure

The Particle Theory

Thu, 30 Mar 2023 06:45:07 +0000

The Particle theory formed due to hypothesis supported by evidence.

The Particle Theory states that:

All matter is made up of tiny particles
The particles are moving all the time
There are forces of attraction holding the particles together
These forces vary in strength in different states of matter.

Observations

•Solids have a fixed shape

•Liquids can change their shape according to their container and flow unlike solids

•Gases have no fixed shape or volume

•Gases can be compressed but solids and liquids cannot.

Question

•How does the movement, arrangement and forces of attraction between particles affect the shape, volume and compressibility of solids, liquids and gases?

Hypothesis

Matter being able to keep its shape and volume and be compressed depends on how close the particles are, their movement and arrangement and the forces of attraction between them.

Predictions

If matter keeps its shape, then particles in it vibrate in fixed positions and are close together with strong forces of attraction.
If matter keeps its volume, then its particles have strong forces of attraction
If matter can be compressed, then its particles are spaced out and have weak forces of attraction

Experiments

In order to test the above hypothesis and predictions, the following experiments need to be done:

•Brownian Motion

Pollen grains in water move about randomly. This proves that liquid water particles are moving about randomly pushing the solid pollen grains around. Specks of smoke move about randomly in air. This proves gas particles in air are moving about randomly in all directions and colliding with the specks of smoke making their movement random. Brownian motion proves that liquid and gas particles can move around.

•Conduction of heat and sound in solids

proves that solid particles vibrate in fixed positions and these vibrations can be transferred from particle to particle in a solid thereby transferring heat and sound energy in solids.

•Particles in solids vibrate faster when heated and when heated to melting point can break free into a liquid state. When heating continues heat causes the particles to move even faster (increase in kinetic energy) and move further apart and after reaching boiling point can become gas

• Pressurizing solids, liquids and gases

Using a syringe to compress solids liquids and gases to prove that the syringe containing gas can easily be pushed in, showing gases can be compressed because their particles have greatest spacing between them.

•Diffusion

Diffusion (is the random movement of particles from where they are many to where they are few) occurring fastest in gases proves that gases do not have a fixed volume and their particles can move away from each other and fill up a container due to their weaker forces of attraction compared to liquids.

Electricity

Thu, 02 Mar 2023 07:24:26 +0000

An electric circuit is a path for electric charge (electrons) to flow along.

Circuit Symbols

Series and Parallel Circuits

In a series circuit, all circuit components are connected in one single loop. If one component gets damaged, the entire circuit gets broken.

In a parallel circuit, there is more than one path around the circuit. There are junctions connecting many branches or loops together in the circuit. If one component in a branch gets damaged, the other branches can still function and the entire circuit does not break.

Current

Electric current is the rate of flow of charge. It is a measure of how many electrons flow every second at a point in the circuit.
An ammeter measures current in a circuit. The ammeter is connected in series in the circuit.

The units of current are Amperes or Amps

Current is the same everywhere in a series circuit.

Current is shared across branches in a parallel circuit. The current entering the circuit is split across the branches and then is added up again so that current leaving the circuit is the same as current entering it.

Voltage

Voltage is the push given to electrons by a power source such as a cell or battery. Voltage is a measure of the energy transferred across each component in the circuit.

Voltage is measured using a voltmeter. The units for voltage are the Volts.

In a series circuit voltage from the power source is shared by the components in the series circuit.

In a parallel circuit voltage is the same across each branch of the parallel circuit.

Resistance

Resistance is a measure of the opposition to the flow of electrons in a circuits. It is the prevention of current in a circuit. Resistance is measured in Ohms by an Ohmmeter.

Wires in a plug

A plug connects a device to the mains electricity supply. The cable between the device and the three-pin plug contains three copper wires that are coated with plastic.

Features of a plug	Function
Outer insulation	All three wires in the cable are bundled together and there is extra plastic insulation wrapped round them all for safety.
Cable grip	This holds the cable tightly in place so that wires do not become loose.
Live wire	Copper wire coated with brown plastic along which the current enters the device.
Fuse	A glass or ceramic canister containing a thin wire that melts if the current gets too high.
Neutral wire	Copper wire coated with blue plastic that also connects to the cable in the wall and completes the circuit.
Earth wire	Copper wire coated in striped plastic that provides a path for current to flow from the case of the device to the ground if there is a fault.

Grounding and Fuses

FUSE

A fuse is an electrical safety device that operates to provide overcurrent protection in a circuit. It’s an essential component that must be present in both Electrical and Electronic appliances.

•Without the earth wire, if a fault occurs and the live wire becomes loose, there is a danger that it will touch the case of an appliance. The next person who uses the appliance could get electrocuted. The earth wire is therefore connected to the case and is attached to a metal plate or water pipe underground. As the wire is made of copper, the earth wire provides a low resistance path to the ground. In the event of a fault, the live current will follow this path to the ground instead of passing through a person. However, this would generate a very large current, leading to intense heating which could start a fire, so a fuse or a circuit breaker is also included in the circuit.

•The fuse contains a thin wire that will melt if the current gets too high in a circuit. If there is a fault that causes the casing of the device to become live, a large current will flow through the live wire and low-resistance earth wire. This high current will also cause the fuse in the plug of appliance to melt.

•Once the fuse has melted, the circuit is broken and no more current flows through the device. This means the case of the device is no longer live and there is no more risk of electrocution. A circuit breaker can serve the same function as a fuse but can be reset without the need for replacement if it trips.

•The fuse or circuit breaker must be connected in the live wire side of a domestic circuit to ensure that it keeps high voltage from reaching the user, or surroundings, if a fault develops.

Acids and Bases

Wed, 01 Mar 2023 08:36:22 +0000

Acids are substances turn litmus paper red and have a pH of less than 7.

Alkalis are substances that turn litmus paper blue and have a pH more than 7. Alkalis are soluble bases.

Acids and Bases can cancel each other out to become neutral. Neutral substances have a pH of 7.

The pH scale measured using Universal Indicator shows the strength of acids and alkalis from 1 to 14.

Pure water is neutral.

The pH of soil affects flower colour.

•Hydrangea flowers are blue in acidic soil with a pH of 5.5 or lower. Blooms are pink if soil pH is 7 or higher.

Indicators

Indicators are substances that change colour in solutions of different acidity and alkalinity.

Examples are:

•natural pH indicators include: Beets: A very basic solution (high pH) will change the color of beets or beet juice from red to purple. Blackberries: Blackberries, black currants, and black raspberries change from red in an acidic environment to blue or violet in a basic environment

•Red cabbage

•Litmus

•Phenolphthalein

•Methyl orange

•Universal indicator

•Litmus, phenolphthalein, methyl orange etc do not show how strong or weak an acid or alkali is, but Universal indicator does.

•Universal indicator is a mixture of indicators that give a range of colours which correspond to the pH of a solution.

•Using a pH meter is a more accurate way of measuring the pH numerically.

•Using pH paper and Univeral Indicator solution shows the colour change and is a simpler way to measure pH.

Neutralisation reactions

This is a chemical reaction where an acid and base react together to form a salt and water.

Acid + Base → Salt + Water

Alkalis are bases that are soluble in water.

Acid + Alkali → Salt + Water

Acids and Alkalis cancel each other out (neutralize)

Neutralization produces substances called salts.

•Hydrochloric acid produce ‘chloride’ salts

•Sulphuric acid produces ‘sulphate’ Salts

•Nitric acid produces ‘nitrate’ salts

Examples of neutralisation reactions:

hydrochloric acid + sodium hydroxide → sodium chloride + water

sulphuric acid + lithium hydroxide → lithium sulphate + water

nitric acid + potassium hydroxide → potassium nitrate + water

Titration

Titrations are often carried out by using a neutralization reaction between an acid and an alkali. <!–

Titrations can tell you the volume of acid needed to neutralise a fixed volume of alkali.

Neutralisation in daily life

Examples of neutralisation reactions in daily life:

•If soil is too acidic, farmers add lime (an alkali) to cancel out the acid and make soil neutral.

•If soil is too alkaline, farmers add manure (acidic) to make soil neutral

•Nitric acid and Ammonium hydroxide (alkali) react to form Ammonium nitrate which is used to fertilize soil (allow plants to grow healthy.)

•Too much acid in the stomach causing heartburn and indigestion can be neutralized by an antacid such as Milk of Magnesia containing magnesium hydroxide (base)

•Toothpaste contains bases like magnesium hydroxide and calcium hydroxide which react with acids in your mouth to reduce acidity.

•Bee stings are acidic and can be neutralized with weak alkalis such as baking soda.

•Wasp stings are alkaline and can be neutralized with a weak acid like vinegar.

•Rust is a base called iron oxide. It can be removed by neutralization with sulphuric acid.

•Acidic waste gases from industries are neutralized by sprays of calcium hydroxide to prevent acid rain.

Note: Acids and alkalis are hazardous. a hazard is something that can cause harm.

•Acids and Alkalis may cause harm. They can be corrosive when concentrated and when dilute can be irritants.

Reproduction

Mon, 09 Jan 2023 07:33:04 +0000

All living things make more of themselves by reproduction.

Fertilization

Fertilization is the fusion of the male and female cell nuclei to form a zygote.

Adaptations of male and female gametes for fertilization

Sperm cells have these adaptations:

•a tail to move them towards an egg cell

•many mitochondria to provide energy

•the head that releases enzymes to digest the egg membrane

Egg cells have these adaptations:

•Large and bulky

•Contains yolk which contains a large food store for zygote.

Internal vs External fertilisation

Internal vs External Development

In summary:

Reproduction in different animals

Human Development and Birth

The fertilized egg (zygote) divides to form a ball of cells called an embryo. The embryo attaches to the lining of the uterus. It begins to develop into a fetus and finally into a baby.

The fetus is protected by the uterus and the amniotic fluid, a liquid contained in a bag called the amnion that acts as a shock absorber.

The Placenta

•The placenta is an organ responsible for providing oxygen and nutrients to the baby, and removing waste substances. It grows into the wall of the uterus and is joined to the fetus by the umbilical cord.

The mother’s blood does not mix with the blood of the fetus, but the placenta lets substances pass between the two blood supplies:

The mother’s lifestyle can affect the developing fetus. For example, smoking reduces the amount of oxygen in the bloodstream. This can lead to low birth weight and premature birth (when a baby is born too soon). Drinking alcohol during pregnancy can harm the developing baby’s nervous system, especially its brain.

Pregnancy cravings can be caused by a number of things, including hormones, a heightened sense of smell and taste, and nutritional deficiencies.

Birth

•It takes about 40 weeks for a baby to develop in the uterus. This time is called gestation. After this, the baby is ready to be born. The muscles in the wall of the uterus contract. Waves of muscle contraction push the baby out of the mother’s body.

Puberty

•The reproductive system of a child is not mature. It needs to change as a boy or girl develops into an adult, so that the system is fully working. The time when the changes happen is called puberty.

•The changes happen because of sex hormones (chemicals produced in the testes of boys and ovaries of girls)

The time between puberty and adulthood is called adolescence.

Here are some changes that happen to both boys and girls:

•underarm hair grows

•pubic hair grows

•body smell gets stronger

•emotional changes

•growth rate increases

Menstrual Cycle in females

•The menstrual cycle involves the preparation of the uterus lining so that it is able to receive a fertilized egg.

•If an egg is fertilized, it can implant itself in the prepared uterus lining.

•If it is not fertilized, the lining of the uterus breaks down and is lost from the body. This is called menstruation or a period.

•The menstrual cycle starts with menstruation (the loss of the uterus lining and some blood.).

• About 14 days after menstruation starts, an egg cell is released from an ovary. This is called ovulation.

•If the egg cell is not fertilized, the uterus lining starts to break down and the cycle starts again.

Energy & Changes

Sat, 15 Oct 2022 18:21:32 +0000

Energy from food

Energy is measured in Joules. We get energy from food. Energy in foods is measured in kiloJoules. It is also measured in kilo Calories. 1 kCal = 4 kJ Different people have different energy requirements per day:

Energy Transfers & Stores

Energy can be stored as:

•Chemical energy in batteries, food and other fuels like petrol/diesel.

•Thermal energy in hot objects

•Kinetic energy in all moving objects

•Elastic potential energy (strain) in objects which are stretched, twisted, bent or compressed (squashed).

•Gravitational potential energy in objects held at high positions.

•Nuclear (atomic) energy inside all materials

Energy can be transferred (moved) from a store of energy) by:

•Forces

•Light

•Electricity

•Sound

•Heating

Law of Conservation Of Energy

Energy cannot be created or destroyed but can only be transferred from one form to another.

Energy flows

•Since energy is conserved, total energy going into the object equals to the total energy coming out from it.

More examples of energy flows in:

photovoltaic solar panels - converts light energy into electrical energy
a greenhouse - converts light energy into t.hermal energy.
a television - converts electrical energy into light and sound energy.
an electric heater - converts electrical energy into heat energy
a car - converts chemical energy into kinetic energy.
playing a drum - kinetic eneryg into sound energy.
an explosion - converts chemical energy into kinetic, sound, heat and light energy.
a torch - converts chemical energy into electrical energy into light energy.
a star - converts nuclear energy into heat and light energy,
a battery charger - converts electrical energy into chemical energy.
a tree - converts light energy into chemical energy.
a microphone - converts sound energy into electrical energy.
a nuclear bomb - converts nuclear energy into kinetic, sound, light and heat energy.
a rocket - converts chemical energy into kinetic energy into gravitational potential energy.
a glow stick - converts chemical energy into light energy.
a ball rolling down a slope - converts gravitational potential energy into kinetic energy.
a generator - converts chemical energy into kinetic energy into electrical energy.
shooting an arrow from a bow - converts elastic potential energy into kinetic energy.
a clockwork toy - converts elastic potential energy into kinetic energy.
a hot air balloon - converts chemical energy into heat energy into gravitational potential energy.
a light mill - converts light energy into kinetic energy.
a wind farm - converts kinetic energy into electrical energy.
a pole vaulter - converts kinetic energy into elastic potential energy into gravitational potential energy.

•Since energy is conserved, total energy going into the system equals to the total energy coming out from it.

Fuels & Energy resources

•A fuel is a substance that contains a store of chemical or nuclear energy that is transferred into heat and light. A fuel is an energy resource.

•Energy from burning fuels is used to generate electricity in power stations. These fuels have been mainly fossil fuels.

FOSSIL FUELS – Coal, Crude Oil and Natural Gas

These are made over millions of years under heat and pressure from layers of Earth over the remains of organisms. Coal is formed from ferns, plants and trees which hardened due to pressure and heat Oil is formed from smaller organisms, like zooplankton and algae. Intense amounts of pressure caused this complex organic matter to decompose into oil. Natural Gas undergoes the same process as oil; however the process is longer and subject to higher amounts of heat and pressure, causing further decomposition. Fossil fuels are non renewable sources of energy because they cannot be replaced easily once they are used up. It takes millions of years to form them.

Renewable Fuels – can easily be made and replaced once they are used up. The rate at which they are used is less than or equal to the rate at which they are made again.

•BIOFUELS – made from plant and animal waste.

•HYDROGEN GAS – can be made from water. Hydrogen combining with oxygen in fuel cells can produce electricity. Water is the only product which makes hydrogen a clean energy resource.

Other Energy resources

•SOLAR POWER – uses energy from sun to:

a) Heat water – solar panels mounted on roofs are tubes full of water which heats up and can be used to heat the building on provide hot water.

b) Produce electricity –

i)solar cells can convert sunlight energy to electricity directly.

ii)A solar power station focuses sunlight using mirrors onto a tower. The concentrated heat from the sun onto tower heats up water, turns it into steam which can drive turbines to generate electricity.

•WIND TURBINES – use the wind to turn turbines to generate electricity.

•HYDROELECTRIC POWER – use flowing water to turn turbines and generate electricity. Moving water in waves and tides can also be used.

•GEOTHERMAL POWER – use the heat from rocks underground to heat water, turn it to steam to drive turbines and generate electricity.

•NUCLEAR ENERGY – uses the energy stored in particles to release heat and light. The heat released can be used to heat water, turn it to steam and drive turbines.

Energy resources depending on the sun

1.Hydroelectricity:

The sun has a store of nuclear energy that is converted to heat and light which we receive on Earth:

To drive the water cycle by using sun’s energy to evaporate water and continue the water cycle (hydroelectric power therefore depends on the sun)

Fossil fuels

Plants use the sunlight energy to convert it to chemical energy by photosynthesis. The chemical energy gets transferred through food chains. When these plants and animals die and get buried under heat and pressure over millions of years they become fossil fuels.

Wind & Tidal energy - Energy from the sun also causes wind and waves.

Energy resources that do not depend on the sun:

1. Nuclear fuels

2. Geothermal energy.

USING RESOURCES

•Renewable energy resources (solar, wind, hydroelectric, geothermal, nuclear, waves and tidal energy) can be regenerated and will never run out but non-renewable energy resources (fossil fuels) are limited and can run out. The rate at which non renewable resources are used up is more than the rate at which they are being formed.

•Burning fossil fuels for energy releases carbon dioxide which is a gas that traps the sun’s heat making the Earth warmer (global warming) leading to climate change.

Energy efficiency

•Not all the energy transferred by a machine is useful. Some of it is wasted.

•The amount of useful energy transferred compared to the total input energy is called the efficiency of a machine.

•An efficient machine has more useful energy transferred than wasted.

•Since an efficient machine wastes less energy and produces more useful energy; it will require less fossil fuel to produce the electricity to run it and so your energy bills will be cheaper.

Mixtures and their Separation

Thu, 13 Oct 2022 07:29:50 +0000

Matter mainly exists as a mixture.

A mixture is made up of two or more components physically intermixed.

75% of the Earth is water in which many different substances can dissolve making it become a solution

Water in rivers and streams may also carry solids such as sand, gravel or mud making it a colloid and suspension.

To make water safe for drinking it must be treated in different ways to remove the unwanted substances mixed in it.

In the first stage of water treatment, waste water (from homes, offices and street drains) passes through a screen, which acts as a sieve to remove large solids such as leaves, rubbish and lumps of human waste, as well as smaller solids.

2: It is then passed through fine filters and left to stand in large ‘settlement ponds’. This stage removes smaller suspended solids that eventually settle out when the water is still.

3: The water from the settlement ponds is still not clean because very small solids are still dispersed in it. Special substances (coagulants) are added to make these solids clump together. They are then easily separated from the water.

4: Disease-causing microorganisms are too small to be removed by filters or settlement ponds. Drinking water may be treated with chlorine to kill them.

Filtration

Filtration is a method used to separate an insoluble solid from a liquid or solution.

The substance from the mixture that is filtered out is called the filtrate. The substance that remains behind in the filter paper is called the residue.

Apparatus:

Method:

A. Fold a circular filter paper in half.

B. Fold the filter paper in half again to form a triangle shape.

C. Open out one layer of the paper to form a cone.

D. Place the filter paper cone into a filter funnel.

E. Place the filter funnel into teh neck of a conical flask.

F. Stir the sand and water mixture so that all the sand is suspended in the water.

G. Pour the sand and water mixture into the filter paper.

Solutions & Solubility

•Substances that can dissolve in a liquid form solutions. In solutions the dissolved substance breaks up into pieces so small that light can pass straight through the mixture.

•A substance that can dissolve in a certain liquid is said to be soluble. Substances that do not dissolve in a certain liquid is said to be insoluble.

solute + solvent = solution

•A solute is the soluble substance

•A solvent is the liquid which is dissolving the solute.

Mass of the solution is the same as the mass of solute plus the mass of solvent at the start. No extra mass is gained or lost. This is known as the law of conservation of mass,

Total mass of the solution = mass of solute + mass of solvent

Salt water solution contains salt as the solute and water as the solvent.

Water dissolves substances from the rocks and soil that it passes through. Water is a very good solvent because many solids, some gases and other liquids can be soluble in it.

•Solids that are soluble (i.e. can dissolve) in water – salt, sugar, coffee

•Solids that are insoluble (i.e. cannot dissolve) in water – sand, flour etc.

•Liquids that are soluble in water – alcohol; acids, alkalis

•Liquids that are insoluble in water – oils, petrol, gasoline, turpentine

•All gases have a certain degree of solubility in water. Some gases like ammonia, bromine, hydrogen chloride and sulphur dioxide are more soluble than oxygen and nitrogen.

•Those solutes that are insoluble in water can be soluble in solvents like ethanol and propanone (acetone).

•There is a limit to how much solute you can dissolve in a particular volume of solvent. If the solubility limit is exceeded, the solution becomes saturated.

•In a saturated solution, the extra solute will sink to the bottom and stay undissolved.

SOLUBILITY

•The solubility of a solute is the mass that will dissolve in 100g of a solvent.

•Factors affecting solubility include:

1.Temperature – the higher the temperature, the more the solubility

2.Type of solvent - 36g of sodium chloride can dissolve in water but only 0.1g can dissolve in ethanol at 20°C

3.Stirring increases speed of solubility

Evaporation & Heating to dryness

Heating a solution until all the solvent has evaporated is known as heating to dryness. We use this methd to separate out a solute from a solution.

Method:

A. Use a medium flame to heat the solution.

B. Wear eye protection while heating to prevent eyes getting burnt from spitting of the solution during heating.

C. Do not fill evaporating dish more than half full with solution.

D. If heating liquid in a tube, make sure open end of tube is not pointing towards anyone.

E. Always use tongs to hold or move hot things.

F. When most of the liquid has evaporated, turn the burner off. Let the rest of the liquid evaporate more slowly.

G. Always set the Bunsen burner to a safety flame when not in use and just before turning off.

Evaporation vs Boiling

Chromatography

Chromatography separates and helps identify different substances found in a mixture.

•After water is cleaned at a water treatment plant it must undergo tests to see what is dissolved in it.

•Chromatography is one of the techniques used in water analysis.

Paper Chromatography

Method:

1.Place a concentrated dot of the solution you are testing on the base line of the chromatography paper

2.Suspend the chromatography paper in a beaker filled with a solvent that can dissolve your solution

3.Make sure the base line with concentrated dot of solution is above the solvent in beaker.

4.Cover the beaker with a lid to prevent the solvent evaporating away.

The solvent soaks up the paper and separates the dissolved solutes in the solution being analyzed. Each solute will be dissolved at different rates. The fastest solute will have travelled the furthest along the chromatography paper.

For analyzing colorless substances, UV light is used to make the solutes glow and become visible on chromatogram.

Uses of paper chromatography:

•Identifying the components in mixtures like water, food , urine, blood, sweat, soil and the atmosphere.

•Testing blood and urine samples of athletes for drugs

•Forensic analysis of crime scenes

Distillation

Drinking water may be made from sea water in a process called desalination. Distillation is a process during desalination in which the sea water is heated so that the water evaporates to form steam leaving behind the salt solutes. The steam is collected and cooled so that it condenses back into pure liquid water containing no solutes.

Factors affecting simple distillation:

•Amount of heat – the greater the heat available, the faster the distillation. Lab distillation is quicker than distillation using sunlight.

•Rate of condensation – Cold water into condenser should come from the bottom of the condenser instead of the top to ensure all the vapour has condensed before it leaves the condenser.

•Boiling point of the substances in the mixture should be far away from each other. The closer the boiling points of the substances in the mixture, the more impure the final product will be.

Cells, Tissues, Organs and Organ Systems

Sun, 05 Jun 2022 08:51:58 +0000

A cell is the smallest unit of life.

Cells of the same type make a tissue.

Different tissues make up an organ.

Different organs work together in organ systems.

Many organ systems make up a living thing – an organism.

Life Processes

All organisms including cells carry out the following life processes.

Movement - they can move from place to place or move parts of themselves. Sunflower plants slowly track the motion of the sun across the sky during the day and then back during the nighttime.
Reproduction - they can make more of themselves. Bacteria are single celled unicellular organisms that reproduce by a process called binary fission.
Sensitivity - they can sense and respond to changes inside and outside their bodies called stimuli around them. Mimosa pudica is a flowering plant of the pea/legume family. The leaves fold inward and droop when touched or shaken, defending themselves from harm, and re-open a few minutes later.
Growth - they can increase in size. Seeds germinate using warmth, water and oxygen and the leaves photosynthesize with the help of water and minerals from soil, carbon dioxide and sunlight.
Respiration - they use glucose and oxygen to release energy. Energy is released when glucose and oxygen react in our cells to produce carbon dioxide and water.
Excretion - they can produce waste and get rid of it. Excretion is the release of waste in the form of urine, sweat and exhalation of carbon dioxide
Nutrition - they require food for energy, growth and overall health.

For anything to be living, it should be able to carry out all the above life processes.

Human & Plant Organ Systems

•Circulatory system helps transport oxygen and nutrients to all body cells via blood.

•Respiratory (Gas exchange) System helps take in oxygen into our body and remove carbon dioxide.

•Digestive system helps break down large food molecules into smaller nutrients that can be absorbed into blood.

•Urinary system helps to excrete waste and extra water from the blood.

•Nervous system helps respond to stimuli by transmitting electrical impulses along nerves.

•Skeletal system helps provide movement, protection and support.

Roots, stem, leaves work together in the plant water transport system

The water transport system in plants takes water from the ground up to the leaves by capillary action.

Water is always flowing from this organ system as leaves constantly lose water by evaporation (transpiration).

Human & Plant Organs

The following are fundamental organs in the human body.

•The brain is the control center of the nervous system and is located within the skull. Its functions include muscle control and coordination, sensory reception and integration, speech production, memory storage, and processing of thought and emotion.

•The heart is a hollow, muscular organ that pumps blood through the blood vessels by repeated, rhythmic contractions.

•The lungs are two sponge-like, cone-shaped structures that fill most of the chest cavity. Their essential function is to provide oxygen from inhaled air to the bloodstream and to exhale carbon dioxide.

•The liver lies on the right side of the abdominal cavity. Its main function is to process and control the contents of the blood. This involves breaking down fats, producing urea, filtering harmful substances and maintaining a proper level of glucose in the blood.

•The stomach is a muscular, elastic, pear-shaped bag, lying crosswise in the abdominal cavity. Its main purpose is digestion of food through production of gastric juices (including hydrochloric acid) which break down, mix and churn the food into a thin liquid.

•The intestines are located between the stomach and the anus and are divided into two major sections: the small intestine and the large intestine. The function of the small intestine is to absorb most ingested food in the blood. The large intestine is responsible for absorption of water and excretion of solid waste material.

•The kidneys are two bean-shaped organs located at the back of the abdominal cavity, one on each side of the spinal column. Their function is to maintain the body’s chemical balance by excreting waste products and excess fluid in the form of urine.

•The bladder is a muscular organ located in the pelvic cavity. It stretches to store urine and contracts to release urine.

Roots - anchor the plant to the ground and absorb water and minerals from the ground.
Stem- holds the plant upright and transports water and nutrients from roots to the leaves.
Leaves - trap sunlight to make food for the plant by the process of photosynthesis.
Plant storage organs e.g. bulbs, storage roots and tubers - store food and water for the plant to use when needed:

Human & Plant Tissues

Tissues contain cells of the same type that perform a certain function.

All organs are made up of tissues. Example: the heart is made up of muscle, nerve, fat and blood tissues.

Nerve tissue - Made up of nerve cells which transmit electrical messages throughout the body
Muscle tissue - made up of muscle cells.
Fat (adipose) tissue - made up of adipose cells. The layer of fat tissue under the skin insulates the body to keep it warm. Pads of fat act as shock absorbers and support and cushion vital organs. The stored fat also provide energy when required.
Epithelial tissue - made of epithelial cells which form the covering of all body surfaces

Plant Tissue

•Root hair tissue absorb water and minerals

•Xylem tissue transports water up the plant from the roots

•Phloem transports nutrients and food up and down the plant and into storage organs

Specialized Cells

Red blood cells - carry oxygen.

Special features

They have a biconcave shape which provides a large surface area for oxygen to pass into them.
They contain hemoglobin which joins with oxygen.
They have no nucleus.

Nerve cells - carry nerve impulses to different parts of the body,

Special features:

They are long and connected to each other.
They can carry electrical signals.

3. Ovum (Egg cell) - this is the female reproductive cell which joins with the male reproductive cell by the process of fertilization during sexual reproduction.

Special features:

It is large
It carries a food store in the form of yolk .in its cytoplasm

4. Sperm cell - this is the male reproductive cell which joins with the female egg cell by the process of fertilization during sexual reproduction.

Special features:

It has a long tail for swimming
It has a head that allows it to enter the female cell.

5. Ciliated epithelial cell - it moves dust particles and germs away from the lungs.

Special features:

It contains hair-like structures called cilia which waft away the germs and dust particles.

6. Root hair cell - it absorbs water and minerals.

Special features:

It is long and thin which provides a large surface area for maximum absorption of water and minerals.

7. Palisade cell - absorbs sunlight for photosynthesis and is found in leaves.

Special features:

Lots of chloroplasts.

Animal & Plant Cells

Cell Organelles & their Functions

All cell organelles are held in the cytoplasm. The cytoplasm is a jelly like fluid that holds all the cell organelles and it is where chemical reactions take place.

Projects | TheScienceTeacher

Combustion

F﻿uels

Food & Digestion

Uses of Nutrients

Food Tests

Balanced Diet

Malnutrition

T﻿he Digestive System

E﻿nzymes

G﻿UT BACTERIA

A﻿BSORPTION

Visking tubing model of small intestine:

Sound

Atoms, Elements & Compounds

ATOM

ELEMENTS

COMPOUND

Molecule –

MIXTURE

Metals vs Non metals

Metal ores – where metals are extracted from

How do elements form compounds?

Ecosystems & Variation

Levels of organisation:

I﻿ndividual → Population → Community → Ecosystem → Biome → Biosphere

How does the environment affect organisms?

How do organisms affect their environment?

I﻿nterdependence

Fitness - Muscles & Breathing

MUSCLES & BREATHING

The gas exchange system

Muscles & Blood

BLOOD

THE SKELETON

Muscles and Moving

DRUGS

SI Units

F﻿undamental SI Units

Derived units (from the fundamental units)

Forces

Friction

Air Resistance (drag force)

W﻿ater resistance

U﻿pthrust

W﻿eight

The force meter – used to measure Force (weight)

Extension and Springs

B﻿alanced and Unbalanced Forces

Resultant Force

Pressure, Force and Area

The Particle Theory

O﻿bservations

Q﻿uestion

H﻿ypothesis

P﻿redictions

Experiments

•Brownian Motion

•Conduction of heat and sound in solids

• Pressurizing solids, liquids and gases

•Diffusion

Electricity

C﻿ircuit Symbols

S﻿eries and Parallel Circuits

Current

V﻿oltage

Resistance

Wires in a plug

Grounding and Fuses

Acids and Bases

I﻿ndicators

N﻿eutralisation reactions

E﻿xamples of neutralisation reactions:

T﻿itration

N﻿eutralisation in daily life

E﻿xamples of neutralisation reactions in daily life:

Reproduction

F﻿ertilization

Adaptations of male and female gametes for fertilization

I﻿nternal vs External fertilisation

Fuels

The Digestive System

Enzymes

GUT BACTERIA

ABSORPTION

Individual → Population → Community → Ecosystem → Biome → Biosphere

Interdependence

Fundamental SI Units

Water resistance

Upthrust

Weight

Balanced and Unbalanced Forces

Observations

Question

Hypothesis

Predictions

Circuit Symbols

Series and Parallel Circuits

Voltage

Indicators

Neutralisation reactions

Examples of neutralisation reactions:

Titration

Neutralisation in daily life

Examples of neutralisation reactions in daily life:

Fertilization

Internal vs External fertilisation

The Placenta

Birth

Puberty

Evaporation vs Boiling

Chromatography