SCIENCE PT-3/TERM-2

curs alongside thunderstorms. Though it might appear beautiful, it kills hundreds of people a year. Lightning is caused due the clouds getting charged by the wind due to friction. Due to this, we can say that the charge developed is electrostatic. Benjamin Frankin was the first person to prove that lighting occurs due to the charged clouds. He performed an experiment in 1572 that is now famously known as the kite experiment. Franklin flew his kite during a thunderstorm and had metal keys attached to the kite. Upon coming in contact, he saw a spark, thus proving that lighting occurred due to the charge of clouds.

Electric Charges

An Electric Charge is a physical quantity responsible for the electrostatic attraction and repulsion between objects / matter / substances. For example, when you brush a comb through dry hair and putt it near chits of paper, you will see the papers get attracted to the comb and stick to it for a bit. Or, when you take of a woolen sweater on top of a nylon shirt, you will notice crackling sounds. If you turn the lights off, you may even see sparks. Sparks are charges that flow through gaps in air. They are hot and thus create light. Or, when you rub a woolen cloth on your head, you can see strands, or your hair start to float. All of these effects are the result of electric charges.

Now, you may ask what causes electric charges. To understand that we need to talk about the composition of matter. Matter is made up of millions of small particles known as atoms. Atoms contain electrons and protons. Electrons are negatively charged while protons are positive. Normally, an object as an equal amount of electrons and protons thus making it neutral. However, when in contact with another object and rubbed against, the friction causes the electrons to move to the other object causing one object to have lesser electrons that protons ( thus making is positively charges ) and the other object having more electrons than protons ( thus making it negatively charged ).

There are two types of charges. Positive and Negative. However, these names have no such meaning and are just used by convention. Let’s learn more about how these charges react with each other with the help of a small activity.

·         Materials Required:

o   String

o   Ballons

o   Pen Refill

o   Woolen Cloth

o   Polythene Bag

·         Aim: Observe the reaction of objects with other objects with charges.

·         Process:

o   Attach two ballons with string and rub them with a woolen cloth.

o   Take two more balloons and run them with a polythene bag instead.

o   Take an ink refill and carefully rub it with a polythene bag and a ballon and run it with a woolen cloth.

·         Observations:

o   In these three experiments performed, we can tell that in the first one, the balloons repel, in the second one, they repel again. However, in the third one, where the charges are different, you can see the refill get attracted to the balloon. This observation, in conclusion, allows us to state that opposite charges attract while same charges repel.

An electrically neutral object can be charged in three ways. By:

·         Friction – When two objects rub against each other, friction is produced. This friction causes the displacement of charges from one object to another. For example, when a silk cloth is rubbed on a glass rod, electrons from the glass rod transfer to the silk cloth making the glass rod positively charged while the silk cloth negatively charged.

·         Convection – Convection occurs when two objects are in direct contact with each other. For convection to occur, one object must be neutral and the other must be charged. For example, when a charged object is touched to a neutral metal plate, it obtains charge. In convection, the neutral object obtains the charge of the charged object.

·         Induction – When a charged body is near a neutral body and is not in physical contact, the neutral object obtains the charge opposite to the one of the charged bodies’.

Objects through which charges can pass through are known as conductors. For example, iron, aluminum, copper, etc. Objects through which charges can not flow through are known as insulators. For example, rubber, wood, etc.

Transfer of Charges

We now know that charges can be transferred through conductors. On the basis of this principle, to understand a little bit about the magnitude of charge and type of charge, the electroscope was created. An Electroscope is made up of a metal plate, connected to a fine metal rod, which is attached to two thin strips of gold / aluminum known as leaves. It is vacuum sealed using a cork and is usually in glass bell jars with the base as a wooden block. When a charged object comes in contact with the metal plate of the electroscope, the leaves may either attract or repel. To demonstrate the working of an electroscope, firstly it needs to be charged with an object of known charge. For example, the comb rubbed on hair. We know that it is negative and se the leaves repel. Now, when another charged object comes in contact with the metal plate, we notice either one of three cases.

1.      Case One – The Leaves attract indicating that the object has a positive charge.

2.      Case Two – The Leaves repel further indicating that the object is of negative charge but of higher magnitude.

3.      Case Three, the Leaves remain the same, indicating that the object is of negative charge and of a similar magnitude.

The transfer of charges from the object to the rod is known as displacement. When an object, directly or indirectly, comes in contact with the earth, it’s charges transfer to the earth. When a conductor is held on one end by our hand and the other on the metal plate, the charges goes through our body and straight into the earth. This makes the leaves return to their original position. The transfer of charges from a charged object to the earth is known as earthing.

What Causes Lightning

We know that lighting occurs as a discharge of energy. To understand why it occurs, let’s go over the cycle first. During a thunderstorm, bits of ice ( frozen raindrops ) form in clouds. These frozen raindrops collide with each other as the cloud moves and obtain charges due to friction. The raindrops with the positive charge accumulate at the top while the raindrops of negative charge to the bottom of the cloud. Due to rain and wind, the ground obtains positive charge due to friction ( collision ) and these charges accumulate wherever there is a spike in the ground. For example, mountains, trees, people, etc. As the charges in the cloud accumulate, the air heats up causing them to jump from the cloud to the ground causing lighting. Lightning occurs between two clouds or one cloud and the earth. Lighting is followed by thunder. The reason we see lightning first and hear thunder next is because the speed of light is faster than the speed of sound. We now know how lighting occurs. But why does thunder? We know that lightning causes air to heat us extensively causing it to expand. This causes vibrations that we hear in the sound of an explosion known as thunder. A lightning strike usually lasts for around 1 – 2 microseconds. The Fear of Lighting is known as Astraphobia while the study of lighting is fulminology. There are a few safety measures against lightning. For example, during a thunderstorm, if in an open place, take cover immediately, stay away from trees, avoid small sheds and try to find big buildings, if in a car or bus, roll down the window and stay away from metal objects, water is the most unsafe during this period. There are also a few things of general awareness to ensure to follow during a thunderstorm. If you see lighting or are in a thunderstorm, find shelter immediately, if you feel your skin tingling or your hair starting to rise, you may be about to be struck by lightning. Squat down to your feet, use your hands to cover your ears and bend down enough so that you don’t need to use your hands or knees. Try to be on your tippy toes as if lighting strikes the ground will reduce the amount of contact you have with the ground. Try to tough your heels together. It is possible that if lighting hits the ground, it goes through one leg, the heel, and out the other. Cover your ears to minimize hearing loss from thunder. If in a forest, find areas with smaller trees, and crouch down. Avoid using traditional phones unless it is an emergency, the same with wired phones, if lighting strikes a phone pole, it may transfer through the phone. Chord – less and mobile phones are safest during this time. Stay away from wired appliances and avoid turning on and off switches. Lighting can flow through then and shock you. Umbrellas are unsafe during this time. Avoid taking a shower as water is unsafe as well. Electric Conductors are long metal rods attached to tall building around 2 – 3 floors higher than the building. This rod protects the building from the effects of lighting. If lightning hits the rod, it flows through it down to a large metal plate in the earth which utilizes the principle of earthing to discharge the charge.

Chemical Effects of Electric Current

Conductivity of Electric Current in Liquids

You might have been cautioned by people around you not to touch electrical appliances with wet hands. How you ever wondered why? It is because water is a good conductor of electricity. Conductors are substances that allow electric current to flow through. Insulators are substances that don’t allow electricity to flow through. Below is a list of conductors and their conductivity.

Light Emitting Diode ( LED )

A Light Emitting Diode ( LED ) is a light source. Hence, it emits light. When electricity flows through it, it turns on. It is also available in many colors and is starting to be used in various industries. An LED Glows even when the electric flow is lesser. This is because, unlike normal bulbs, it need not heat anything to glow. An LED has two LEADs. The Longer one is Positive while the Shorter one is Negative. We must ensure that these leads do not touch each other.

Testing the Magnetic Effect of Electric Current

To test or to prove the magnetic effect of electric current, we can do a simple experiment. To do this experiment, we require a magnetic compass, a copper wire that is not insulated, a battery, and a switch ( optional ). We first start by assembling the circuit. We connect the switch, battery and wire together and then put the compass near them. Before closing the circuit, observe the direction in which the needle of the compass is pointing. Next, turn on the circuit. You can see the needle deflect and change it’s direction. This proves the magnetic effect of electric current.

What Makes Liquids Conduct Current

We know that matter is made up of atoms. Atoms then consist of nucleus and surrounding orbits. The Nucleus is heavy and at the center of the atom. It then consists of protons which are positively charged and . The Surrounding orbits have many electrons which as negatively charged. Generally, an atom consists of an equal number of electrons and protons. However, under certain conditions, they may obtain or lose charges from / to other atoms. When atoms lose electrons, they become positively charged. But, when atoms gain electrons, they become negatively charged. An Atom, or a Group of Atoms of positive charges are known as cations. An Atom, or a group of Atoms of negative charge are known as anions. In an Acid, Base, or salt, both positive and negatively charged atoms should be present to make it a conductor of electricity. For example, in salt ( NaCl ), Sodium ( Na + ) is a cation while Chlorine ( Cl - ) is an anion. Therefore, Salt is a good conductor. However, substances like sugar, kerosene, and alcohol ( which lack both atoms ) are insulators due to this requirement. To test whether a substance is a conductor, we need to first make it into a solution, then, connect two non – insulated wires with open Ends into the substance. Join the other end of wire one to a battery and the battery to an LED, join the other end of wire two to the LED. If the LED glows, it has both present, if not, it does not.

Electrolysis

When a conducting substance has electricity passed through it, certain reactions occur ( chemical ). These reactions are the chemical effects of electric current. For example, salt when dissolved into water forms ions. The positive ions are known as cations while the negative ones are known as anions. The rods through which electricity is passed through to the substance are known as electrodes. They are usually made up of graphite or metal. The positive one is the anode while the negative one is the cathode. The Substance through which electricity is passed through is known as the electrolyte. When electricity is passed, the cations ( + ) move to the Cathode ( - ) while the Anions ( - ) move to the Anode ( + ). This movement of ions is known as electrolytic / ionic conduction. This process is known as electrolysis and this system is known as an electrolytic cell. Therefore, electrolysis can be defined as the decomposition of a substance upon passing electricity through it. So, let’s get back to the example of Salt. When Salt ( NaCl ) is poured in the water, it forms Cations ( Na + ) and Anions ( Cl – ). When electricity is passed through it, here are the reactions that occur:

NaCl à Na⁺ + Cl^-.

At Anode: Na⁺ + e^- àNa.

At Cathode: Cl^- – e^- à Cl.

The Whole Reaction: 2NaCl à 2Na + Cl₂

Electrolysis of water can be done using a simple experiment. This experiment was first done by William Nicholas in the year 1800. Start by taking a beaker. Put 250ml of water in the beaker and take 2 iron nails or graphite sticks from a previous clean electrolysis. Use some sand paper and rub it across the rods. Put the rods in the water but ensure that 1/4^th of it is out the water. Next, add some salt. Not a lot, just a pinch. It will be used as our electrolyte. Connect a battery and observe gas bubbles coming around both electrodes. They are hydrogen and oxygen bubbles. Below is the reaction:

H₂O à H⁺ + OH^-

At Cathode: 2H⁺ + 2e^- à H₂á

At Anode: 4OH – 4e à O₂ á + 2H₂O

Overall Reaction: 2H₂O à 2H₂ + O₂

Electroplating

The Process of depositing a layer of metal on another object by the means of electricity is known as electroplating. It can be done to protect materials from corrosion, or to make materials more attractive. For example, gold plated jewelry, or the shiny handles of bikes. To display electroplating, we can do another small experiment. Start by taking two strips of different metals. For this example, I will take copper and iron strips. To clear them of impurities, rub them with sand paper. Set Copper to be the anode and iron to be the cathode. The electrolyte to be Copper Sulphate. When Current is passed through, the copper sulphate forms into ions and the copper ion ( + )gets attracted to the cathode thus slowly plating it with a layer of copper. As this experiment goes on, you will notice the copper strip getting thinner and thinner as it replenishes the copper ions in the copper sulphate, while the iron strip obtaining a new layer.

Electroplating has various uses. A few of which are:

·         Electroplating car parts, wheel rims, handles, cycle bells, etc with chromium to prevent corrosion.

·         Electroplating Iron and Copper with Gold or Silver to make inexpensive Jewelry.

·         Electroplating Iron food cans with tin as tin is less reactive to food and will not spoil it.

·         Electroplating Iron Bridges with Zinc ( Galvanization ) to prevent it from rusting.

·         Electrolytic Refining

Electrolytic Refining

The method of electroplating, when done with different techniques, can purify metals. The process of purifying metals using electric current is known as electrolytic refining. Let’s learn this via an example. Take a strip of impure copper and a thin strip of pure copper. Put the impute copper at the anode and the pure copper on the cathode. Let copper sulphate be the electrolyte. Once you connect the battery, The copper sulphates cations get attracted to the cathode while the impure copper’s copper is used to replenish the copper sulphate. After some time, you will notice the pure copper getting thicker and a pool of impurities ( anode mud / sludge ) and the bottom of the cell.

Force and Pressure

Force – A Push or Pull

A Force is either a push or a pull that results in the change of an objects state of rest, direction of motion, speed, and / or shape. To apply Force, a minimum of two things need to interact with each other. For example, when a golf ball is hit, a golf club is used, when a football is kicked, out feet are used, when we squeeze a toothpaste, our hands are used. Based on these experiments, we can infer that force requires the interaction of two or more bodies.

Effects of Force

There are 4 main effects of force. They are:

·         Force Changes the State of Rest in an Object – When a Foot Ball that is at rest is kicked, the football starts moving in the direction it was kicked and after some time, reobtains it’s state of rest.

·         Force Changes the Speed of an Object – When a Goal Keeper wants to stop a football, they apply force in the opposite direction. Applying force in the direction an object is going will make it faster while applying force in the opposite direction will make it slower.

·         Force Changes the Direction of an Object – When, in cricket, the bats person hits the ball, the ball changes it’s direction and goes in the direction the bats person hit it. The same can be seen in football. To change the direction of the ball, people kick it in the direction they want it to move. Hence, they apply force.

·         Force Changes the Shape of an Object – Upon Crumpling a piece of paper, pressing a tube of toothpaste, or pulling clay apart, the force applied causes change in the shape of the object.

Types of Forces

There are different types of forces. They are classified on the bases on how they are applied. For example, when you press a balloon or pop a balloon using a needle, you are in direct physical contact with the balloon. However, when an apple falls from a tree due to earths gravitational pull, the apple and earth are not in contact during the application of force. Therefore, it is a non – contact force. By these examples, we understand that we can classify force into two types on the bases of how it is being applied. They are:

·         Contact Force – Contact Force is a force in which both the objects are in direct or indirect contact with each other. For example, the squeezing of lemons using our hands. Two examples of contact forces are:

o   Muscular Force – Walking, Running, Pulling, Pushing, or any force that is done with a human or animal bodies muscles are known as muscular force. For example, throwing a ball. A ball cannot be thrown by a human without having muscular / physical contact. This makes this a contact force.

o   Frictional Force – Friction, also known as frictional force, is a force applied on an object that usually slows it down or stops it. It occurs due to tiny irregularities in the surfaces of the objects colliding with the other object’s irregularities therefore slowing it down. When a ball is rolled on the ground, the force applied by the ground that eventually causes it to stop is known as frictional force.

·         Non – Contact Force – When two objects need not come in contact to exert a force, they come under non – contact force. For example, an apple falling down to the earth even though the earth Is not in contact with the apple. The area in which only can something apply non – contact force is known as field of influence. Three examples of Non – Contact Forces are:

o   Magnetic Force – Magnetic Force is the force exerted by a magnet on another magnet and / or magnetic substance within its field pf influence. Though this may not be seen at first, it can be observed when iron nails are brought near a magnet. The field / area in which a magnet can act its force upon Is known as its magnetic field. This property f magnets is used for various things / in various places. For example, junkyards. A bar Magnet has two poles. Opposite poles attract while like poles repel.

o   Electrostatic Force – Electrostatic Force is a force exerted by a charged body on another charged or uncharged body. In Electrostatic Force, the charged body can either attract or repel other bodies. It also has a field of influence known as the electric field. We can demonstrate this using a simple experiment. Start by taking a comb and brushing it through dry hair 5 – 10 times. By doing this, the comb becomes charged by friction. Upon bringing it near paper, the paper gets attracted to the comb causing it to get stuck to the comb for a few seconds.

o   Gravitational Force – Gravitational Force is the pull of Force. It is found in every object that has mass. For example, the earth’s gravitational pull what is allowing us to walk conveniently without floating off. Any object that we throw up will always come back down. This is because the earths center is always trying to pull objects down and close to it. The larger the mass of an object, the more the gravitational pull it exerts.

Weight of an Object

The width of an object is the measure of the gravitational pull on the object. Upon using a spring balance, the number derived is the amount of gravitational pull a body ( earth ) is applying on the object. More the pull, more the weight. This is why bigger rocks are heavier than smaller rocks. To measure weight using a spring balance, we must attach an object and then let it suspend freely. Weight and mass are two very different quantities. Weight is the amount of gravitational pull felt by an object while mass is the material content of the body. The gravitational pull of the moon Is 1/6^th that of the earths. So, if you weigh 42 kgs on earth, you weigh 7 kgs on the moon.

Unit of Force

The SI unit of force is Newtons ( N ) named after the famous scientist Sir Issac Newton ( Discovered Gravity ). However, the Unit of Kilogram Weight ( Kg-wt) is also a unit of force where 1kg-wt = 9.8N.

Resultant Force

At one period of time, there is not a limit to the number of forces that can act on an object. However, You will not be able to feel these forces individually, you will feel it all as one force instead. This one force is the resultant force. The Resultant force is the force an object is felt due to other forces. To make it simpler to understand, we can illustrate it with three examples.

1.      Two Forces are Acting on the Same Object in the Same Direction on the Same Line – Let’s Say person A is pushing a cupboard north with the force of 100N. The Cupboard is moving, but is moving slowly. Person B joins person A and uses 150N of force to push the cupboard with him. The force applied on the cupboard will therefore be F = F₁ + F₂ = 100N + 150N = 250N. Now, the cupboard is moving much faster.

2.      Two Forces Acting in the Same Line, on the Same object, In opposite Directions – Let’s take the previous example. But instead of person B helping Person A, They are opposing them. Then, the force felt on the cupboard will by F = F₁( Greater Force ) – F₂( Lesser Force ) = 150N – 100N = 50N and the cupboard will move in the direction of greater force ( in this case B ).

3.      Two Forces Acting in the Same Line, On  the Same Object, It opposite Directions, with the same amount of force – If person A Gets as strong as person B, their forces will add up to 0 Causing the cupboard to stay at rest.

Pressure

Why is It easier to cut an apple with a knife than with a ruler? This is because the ruler has more area to distribute the force making it require more force to cut. However, a  knife keeps the force concentrated, making it easier to cut. Pressure is, therefore, the outcome or result of force. The SI Unit of Pressure is Pascal ( Pa ) named after the French mathematician and Physicist Blaise Pascal due to his contributions in the field. Force is also defined as Force per Unit Area. This is because  . Pressure is responsible for many important things we see today. For example, Some very important and useful devices operate on the principle of pressure. A few of the applications of pressure are:

·         Needles and Pins having sharp edges to make it require less force / easier to penetrate the paper / cloth.

·         Knives, pins, and cutters are sharpened to reduce the area making the same amount of force exert more pressure. The amount of pressure reduces as the knife gets blunter ( the area increases ).

·         School and Laptop bags have broad padded straps to evenly distribute the weight of the objects inside them making them lighter and easier to carry on the shoulders.

·         Syringes are used to take blood for blood tests as when they are pushed into the skin, the liquid ( blood )forces itself to move into the syringe when the plunger is withdrawn as it creates a low pressure zone ( vacuum ) which the blood fills.

·         Skis are broad so that the weight of the person gets distributed, and the pressure applied on the snow gets reduced. This ensures that the person does not sink into the snow.

·         A camel has large – padded feet so that the pressure exerted on the sand is distributed, making the camel to not sink into the sand.

·         The feet of elephants are broad to hold their weight.

·         Since water pressure increases with depth, the base of the Dam needs to be broad and strong.

·         Porters place a thick folded spiral cloth on their heads to evenly distribute the weight of the objects on top of their heads.

Pressure Exerted by Fluids

Anything that flows is defined as a fluid. Liquids and gases can flow. Hence, they are considered fluids. Solids, however, can not flow. Fluids have mass and weight as well due to the force of gravity. These Fluids exert pressure as well. For example, upon inflating a balloon with air, the air inside is applying pressure on the walls of the balloon causing it to expand and grow. However, when too much pressure is put by the air to a point where the balloon can’t withstand it, the balloon pops. Similarly, when you try to push a balloon full of air in a bucket, the water in the bucket puts up great resistance that caused the balloon to float back up.

Let’s learn a little bit more about pressure exerted by liquids through various Activities:

·         Liquids exert Pressure on the Walls of the Container – Take a bottle, create a small hole in the center, attach a pipe there and connect the pipe to a balloon. You will see the balloon start to partially inflate and with water. This proves that liquids exert pressure on the walls of containers.

·         The Amount of Pressure exerted on the Bottom of the Column Depends on the Height of the Liquid in the Column – Take a transparent tube with both ends open. On one end, attach a ballon and leave the other end open. Start pouring water in the tube. Stop at around 1/4^th the way to the top of the tube. You will see the balloon inflate a little. Add more and move water and observe how the size of the balloon changes.

·         Liquids exert more Pressure as the Depth Increases – Take A Bottle of water, Poke three holes at different depths. Upon filling it up with water, you will notice that the bottom hole shoots water much further, the highest one shoots it the closest and the middle one between the two. Around 1000m in the ocean, the pressure exerted by liquids is 100 times the atmospheric pressure of earth. So, to avoid getting crushed, divers need to wear special suits.

·         Liquids exert Equal Pressure on Equal Points of the Container – Take a Bottle of water. Poke holes on all four sides at an equal depth. You will notice that the distance that the water is flowing is equal on all sides of the bottle.

To measure liquid pressure, a device known as a manometer is used. It consists of a U shaped tube ( usually containing mercury ) attached to a pipe that is put into liquids. But, when doing this at home, replace the mercury with water, and notice the water level rise as you go deeper.

Gasses, just like liquids, exert pressure as well. For example, the pressure exerted on the tyres of cars, pressure exerted on the walls of the ballon upon inflation, etc. A tyre looses air when pricked with a needle, proving that the air inside is exerting pressure on the body.

Magdeburg Experiment

A German scientist conducted a famous experiment at Magdeburg to show how large atmospheric pressure was. During this experiment, he connected two identical spherical hemispheres 51cm in diameter. He then smoothened them out and utilized a vacuum pump to suck out all the air. Then, 8 horses were employed on either side of the hemisphere who were asked to pull it apart. However, the atmospheric pressure was so large that they could not separate it.

Atmospheric Pressure

We have studied about the atmosphere in previous classes. It is the layer of air around the earth. The atmosphere extends several kilometers above the Earth's surface. Since air has weight, it exerts pressure on the surface below it. So, atmospheric pressure can be defined as the pressure exerted on an object by the weight of the air above it. We can see atmospheric pressure by performing a simple experiment. First, take a bowl and fill around half – 1/4^th of it with water. Next put a candle in the middle and cover the candle with a glass jar. The lit candle will start using the oxygen which makes the atmospheric pressure in the jar lesser that it is outside causing the air to exert pressure on the water which causes a sudden rise in water level inside the jar. This proves that the atmosphere exerts pressure. Atmospheric pressure is roughly 1 * 10⁵ N/m². Atmospheric pressure decreases with a rise in altitude. A few places where atmospheric pressure is used are:

·         Vacuum Cleaners – When the fan inside runs, it pushes the air out creating a low pressure zone which the air and dust particles fill.

·         Rubber Suckers – When a good quality rubber sucker is pressed down on a surface, the air between the surface and the sucker escapes creating a low pressure zone making it harder to pull out.

·         Straws – When we suck from a straw, a low pressure zone is created which causes the liquid to get pushed up through the straw and into our mouths.

·         Syringes – When the piston of the syringe is retracted, a low pressure zone is formed in the tube. This causes the atmospheric pressure to push the fluid up to take the place of the low atmospheric pressure zone.

Cell – Structure and Functions

Cells – Shape, Size, and Number

A Cell is the Structural and Functional Unit of every Living Organism. Every organism starts of as one cell. Over Time, they divide to form new cells, which for tissues, slowly forming organs, and then forming an organism. Therefore, they are the structural unit of a living organism. These cells also carry our life processes such as Respiration, Digestion, Excreation, etc. These Process show that a cell is the functional unit of a living organism as well.

Shape – The Shape of a cell varies based on it’s job. For example, most cells are spherical, cuboidal, flat, thin, and / or long. Cells such as Red Blood Cells ( RBCs ) are thin, disk shaped. While muscle cells are long and thing as they need to expand and contract a lot. Amoeba, a single cellular organism ( unicellular ) keeps on changing it’s shape. It does this to move and to capture its prey. Nerve Cells are long with multiple branches. This is because they need to be able to quickly transmit signals all over the body.

Size – The Size of a cell also varies. For example, the ostrich egg is the largest cell while bacteria is the smallest. The size of a cell does not affect the size of the organism. They are not at all related. For example, both cow’s and birds nerve cells are long and branched.

Number – Organisms can be classified into Unicellular Organisms and Multicellular Organisms. Unicellular Organisms are organisms in which only one cell is present. They are usually microscopic organisms. Uni means one, while cellular means cell. For example, Chlamydomonas, amoeba, paramecium, etc are unicellular organisms. They perform all life functions such as digestion, respiration, excretion, and growth from that one cell. Multicellular organisms are organisms that have more than one cell. For example, Humans, Big Plants, Animals, etc are multicellular. They have millions and billions of cells present, and the cells work together to carry out life processes.

Life Span – The Life span of cells can vary based on their habitat and functionalities. Some cells in the digestive track only survive for a few days, while white blood cells usually survive for six weeks. Pancreatic Cells can also survive for a year.

Observing Cells

We know that cells are usually very small and can not be observed directly from the naked eye. To observe cells, a device was created known as a compound microscope. It obtains its name due to the fact that it uses two lens’ to magnify. The two lenses are the eyepiece lens and the objective lens. These lenses together enlarge the image of organisms significantly. To magnify a cell, firstly, a clear slide is taken. On the center of this slide, the specimen is put. A Specimen can be a tissue or cell of an organism. 1 – 2 drops of water is then added and a thin slip known as the cover slip is put on top. Then, upon putting this slide under the microscope, we can see small cells. To make it easier to observe internal organelles of cells, or even some cells themselves, the cells are stained with chemical dyes such as safranin, methylene blue, iodine, and crystal violet. This provides the cell with a hint of color thus making it easier to observe. Let’s try this with the help of an activity. Take an onion and cut it into thin strips vertically. Then, take one of these strips and break it into two using the twist and pull method. This will leave thin, thread like objects on the end of one piece / both pieces. Use tweezers and carefully pull out this membrane and get it ready on a slip. Stain it with safranin and you will be able to observe brick wall like things.

Cell Structure

We now know that cells, externally vary in shape and size. However, internally, their structure is almost the same for all cells. A cell is made up of A Cell Membrane / Cell Wall, Cytoplasm, and Nucleus. Let’s Go deep into each of these topics and learn some more about them:

·         Cell Membrane – A Cell membrane is the outermost covering or a cell. It is thing and delicate made up of proteins and lipids. It is also known as the plasma membrane. Here are Some of its functions:

o   It is the outer covering that separates a cell from the outside and protects the cell.

o   It is permeable. It allows certain substances to enter and certain to leave. For example, oxygen and other nutrients to enter and carbon dioxide to exit. This makes it selectively permeable.

o   It gives shape to the cell.

o   It Provides the cell with rigidity and support.

·         Cell Wall – In addition to Cell Membranes, plant cells have a cell wall. Since plants can not move, they have to sustain the effects of the environment. This cell wall is made up of a carbohydrate called cellulose. It provides the cell with a hard outer covering.

o   It protects the cell from atmospheric effects such as wind, rain, dust, etc.

o   It gives shape to the cell.

o   It provides the cell with rigidity and support.

      Now, let’s compare both cell membrane and cell walls:

·         Cytoplasm – Cytoplasm are jelly like structures that separate the nucleus from the cell membrane. Cytoplasm consists of many small organelles that perform all the functions of a cell. Therefore, the cytoplasm performs all life functions of a cell.

·         Nucleus – The Nucleus is an oval shaped / spherical shaped component of the cell. It is one of the most important components of the cell as well. It consists of an outer covering called the nuclear membrane. This membrane separates the nucleus from the cytoplasm. This membrane is also selective permeable and only allows certain things to go in and out. The Nucleoplasm is the fluid part of the nucleus. The nucleus also contains a nucleolus at its center. The Nucleolus is important as it manufactures proteins. This can only be seen under a microscope. The Nucleus also contains thread like structures known as chromatins. During cell division, these chromatins split to form rod like structures known as chromosomes. These Chromosomes contain Genes. Genes are certain characteristics that are inherited from the parent organism / cell to the offspring. When parents have different genes, new features can be found in the offspring. Genes control the living function of the cell. Which is why the nucleus is known as the controller of all living functions of a cell. On the basis of the presence of a nuclear membrane, cells can be classified as Prokaryotic or Eukaryotic. Pro means Primitive and Karyotic means nucleus. A Prokaryotic cell does not have a nuclear membrane or has genes present outside the nucleus. For example, blue algae. Eu means Present, and Karyotic means Nucleus. Eukaryotic cells contain a well – organized nucleus a nuclear membrane present.

The Living parts of a cell are called protoplasm. They include the cytoplasm and nucleus. The protoplasm is thus the living part of the cell. Non living things such as water and minerals in a cell are known as cell inclusions.

Cell Organelles

The cytoplasm of a cell contains many small structures known as cell organelles. These organelles are responsible for performing life functions such as digestion. Let’s Learn more about some cell organelles:

·         Endoplasmic Reticulum – The Endoplasmic Reticulum is a fine network of pipes that transport substances such as food and water around the cell.

·         Ribosomes – Ribosomes are attached to the Endoplasmic Reticulum and are responsible for the absorption of proteins and the synthesis of proteins.

·         Plastids – Plastids are only present in plant cells. They are of various types.

o   Leucoplasts – Leucoplasts are Responsible for storing food and nutrients in a plant cell.

o   Chloroplasts – Chloroplasts are Important for plant cells as they contain a green pigment known as Chlorophyll that is responsible for the process of photosynthesis.

o   Chromoplasts – Chromoplasts are the red, yellow, or other color giving parts of the cell. They provide color to parts of leaves, flowers, and fruits.

·         Lysosomes – Lysosomes are responsible for the killing / removal of old cells. They are therefore known as suicide bags. They are sac – like structures.

·         Mitochondria / Mitochondrion – Mitochondria is an important part of a cell. Singular – Mitochondrion. It produces energy during respiration and is therefore known as the powerhouse of the cell. It is not present is Red Blood Cells and Bacteria.

·         Golgi Apparatus – Golgi Apparatus or Golgi Body is a tube like structure responsible for the storage and excretion of substances.

·         Vacuoles – Vacuoles are hole like structures in cells ( present only in the cytoplasm ) that are responsible for the storage of food and other substances.

·         Centrosomes – Centrosomes are structures responsible for managing / looking over the process of cell division. They are only present in animals.

Plant vs Animal Cell

Both Plant and Animal Cells have a nucleus, cytoplasm, cell membrane, and a nuclear membrane. However, Plant cells are usually larger than animal cells due to the addition of the cell wall. Below are some comparisons of both plant and animal cells:

Cell Division

Cells, after reaching a certain size divide into two new cells known as daughter cells. The Process first starts off with the nucleus slowly dividing into two. Followed by the chromatins forming chromosomes. Then, after some time, the cell splits into two cells. In animal cells, the centrosome regulates this process. Cell division leads to the growth of an organism and repairs damaged cells. This is why it is so important. All Plants and Animals grow due to this. However, after a certain age, cells divide less and do not cause growth. In humans, our skin cells keep dividing and dead skin cells keep getting replenished.

Discovery of the Cell

In 1665 Robert hook was the first person to observe a cork ( part of the bark of a tree ) under a magnifying glass. He then proceeded to observe the same cork under a microscope. He noticed many small honeycomb – like structures present and named these boxes as ‘cells’. A few years later, a Dutch scientist Antonie Van Leeuwenhoek observed these cells under his self – made microscope and observed many organism’s cells, bacteria, reb blood cells, protozoa, etc. However, the discovery of cells was proved by Theodor Schwann and Matthias Schleiden that in 1838 – 1839 proving that all organisms are made up of cells.

Light

Reflection Of Light

The reflection of light is a phenomenon that states that light bounces back from a surface when shone upon one. This takes place effectively when light strikes against a polished surface. A plane mirror is a good example of a polished surface. As we go deeper into this lesson, there are a few terms we need to be familiar with.

·         Incident Ray – The Ray of light that strikes the polished surface is known at the incident Ray.

·         The Point of Incidence – The point at which the Ray of light meets the polished surface.

·         The Normal – An Imaginary perpendicular line drawn vertically from the point of incidence.

·         The Reflected Ray – The ray of light that has been reflected ( bounces back ) from the polished surface.

·         Angle of Incidence – The Angle formed between the incident ray and the normal line.

·         Angle of Reflection – The Angle formed between the Reflected ray and the normal line.

Laws of Reflection

For a reflecting surface, there are two main laws that are followed when light strikes. It is impossible to go against these laws. The Two laws are:

·         The Incident Ray, Normal, and Reflected ray are all found on one plane.

·         The angle of Incidence is equal to the angle of reflection.

We can prove these laws with the help of a small activity. Start by taking a piece of paper and drawing a line MM’ on it. On the middle of the line, draw a point. This will be Point O. Point O will be the point of incidence. Next, draw a dotted line perpendicular to MM’ from point O. This will be your normal. Place a plane mirror vertically on the line MM’. Finally, Take a Lazar light and shine it at point O. Mark the angle you shine it at. Observe the angle it is reflected at and mark it as well. Measure both angles and you will notice that they are equal. Keep changing the angle you shine the lazar at and notice the exact same thing repeat.

Plane Mirror

A plane mirror is the most common kind of mirror. We often look into it to leek at ourselves. To make a plane mirror, a sheet of clear glass is taken. This sheet is then painted with silver paint on one side, and the silver paint is then coated with another layer of colored paint. The glass provides a smooth surface for the light to reflect off of, the silver paint provides a shiny coating and reduces the amount of light lost ( amplifying the reflected light ), followed by the paint coat which protects the silver coating and reduces the loss of light. By following these steps, we can make a plane mirror. The refection formed by the mirror is known as the mirror image or the image. A plane mirror has certain characteristics that can be seen upon observation. They are:

·         The Image is always erect and of the same size as the object.

·         The Distance between the mirror image and the mirror is equal to the distance between the object and the mirror.

·         The Image is  always Virtual. Hence, it can’t be obtained on a screen.

·         The Image is laterally inverted. This means that right appears as left and left appears as right. This is why the word ABULANCE is written inverted on ambulances. This is because when drivers look into the rear view mirror, the inversion gets inverted displaying the word AMBULANCE properly thus making it easy to read and less distractive.

Types of Reflections

Through this lesson we will be mainly covering the reflection of light off of plane surfaces or mirrors. But have you ever wondered what happens to an image when it’s reflected from an irregular surface? Let’s learn more about it!

·         Regular Reflection - Regular Reflection occurs when the reflected rays are parallel to each other. This is usually seen on smooth surfaces or plane mirrors.

·         Irregular Reflection or Diffused Reflection – Irregular Reflection also known as diffused reflection occurs when the reflected rays are not parallel to each other. This can be seen on rough surfaces and is caused due to the irregularities on the surface.

If you wonder if reflected rays can further be reflected, the next paragraph will give you the answer with examples! Yes, reflected rays can be further reflected. But this only occurs if the reflected rays reflect on other mirrors as the angles of incidence. This phenomenon is used at barbet shops to show customers the back of their haircut. It is also used to make a device known as a periscope. A periscope is a device that lets us see over restrictions. It utilizes two plane mirrors attached at 45 degree angles each. The first mirror reflects the image onto the second mirror which reflects in into our eyes thus allowing us to see the image. This is used in submarines to look over the water and in army bunkers and tanks to look for enemies.

Multiple Reflections

When an image gets reflected multiple times from multiple mirrors, it forms multiple reflections. When two mirrors are connected, in the middle, the angle between them is used to determine the number of images formed. To Determine the number of images formed, this formula is used:

For example, the angle between the mirrors is 60 Degrees. Then the number of images formed will be (360/60) – 1 = 6 – 1 = 5.

A Kaleidoscope is An instrument that uses this phenomenon. It usually consists of three rectangular mirrors connected to one another which are enclosed in a cardboard casing of similar size followed by a hole on one side, a translucent sheet, beads, covered by a transparent piece of plastic on the other side. Upon observation through the hole, we can see symmetric patterns being formed.

Refraction of Light

When light travels through different mediums, it’s direction changes. This is because the speed at which light travels through different mediums is different. This causes images to look different or weird. The speed at which light travels through a vacuum is 3 * 10⁸ m/s. However, it reduces while going through different mediums causing the ray of light to bend. The phenomenon of the bending of a ray of light upon passing through different mediums is known as refraction.

Dispersion of Light

Upon shining wight light or sunlight through a glass prism, seven colors can be seen. It appears as if the white light / sunlight is being split into these seven colors. This is because the glass is refracting the ray into these colors. The band of colors is known as the spectrum. The Spectrum consists of 7 colors known as VIBGYOR which is an acronym for Violet, Indigo, Blue, Green, Yellow, Orange, and Red. We can see dispersion of light when a CD ( Compact Disk ) is exposed to light, or sometimes in water droplets, and even in rainbows in which the raindrops act as the medium through while the light is dispersed.

The Human Eye

The Human Eye is one of the 5 sense organs and is one of the most important ones. For the rest of this lesson, we will be talking about our eye and going deeper into its functions. We humans have two eyes which as places in the eye ball socket in our skull. Let’s learn a little about the parts of the eye:

·         Cornea – The Cornea is a transparent covering on top of the iris, pupil, and anterior part of the eye.

·         Iris – The Iris is a circular disk in inside the cornea. The pupil is located inside this. It is what gives color to our eyes.

·         Pupil – The pupil is a gap in our iris through which light passes through into our eyes.

·         Lens – The lens is just behind the pupil. It allows for the light to get refracted and focused on the retina where the image is perceived.

·         Retina – The Retina acts as a screen at which the light is focused on. The retina is connected to the optic Nerve. The point in which the image is focused on the retina is known as the yellow spot. It is highly sensitive. The retina consists of two cells that allow for the perception of the image. They are rod shaped cells and cone shaped cells.

o   Rod Shaped Cells – Rod Shaped Cells allow for the perception of images in low light conditions such as night.

o   Cone Shaped Cells – Cone Shaped Cells allow for the perception of images in bright light such as the day. They also allow for the perception of color.

·         Optic Nerve – The optic nerve is the nerve that transmits signals from the retina to the brain to be interpreted as images. It is very important.

·         Optic Blind Spot – The point at which the optic nerve meets the retina is known as the optic blind spot. This area lacks the presence of rod shaped and cone shaped cells.

·         Vitreous and Aqueous Humour – The Aqueous Humour is a thin layer of liquid between the Cornea and the lens. The Vitreous Humour is a layer of liquid that allows for the refraction of light. It is present between the lens and the retina.

How our Eyes See

The rays of light first start by entering our eye using the pupil. They go through the lens and the vitreous humour which refracts them and focuses it on the retina. The rod Shaped Cells and the Cone Shaped Cells Then interpret this image and send it through the brain through the optic nerve in the form of electrical signals. These get interpreted by the brain as the images we see. Our eyes act as a camera, but the image perceived by the retina is inverted. The brain has to invert it to the image we see.

Defects of Vision

Out eyes are provided with eyelids to protect them from foreign particles damaging them. Our eyes also have the ability to adjust the thickness of the lens to see further and closer objects. This ability is known as the accommodation of power in our eyes. Our eyes can focus up to 25cm without strain and lower that that will cause strain. However, due to certain irregularities, or age, our eyes slowly loose this ability, and we start developing things known as defects of vision.

Myopia and Hypermetropia – When the eyes can not see far off in the distance but can see close by, this defect is known as Myopia or short – sightedness. To correct this, we wear glasses with a concave lens. Whenever we can see objects far off but not closer objects, it is known to be hypermetropia or long – sightedness. To correct this, we wear glasses with a convex lens.

Cataract – Another Defect of vision coming with age is cataract. Cataract is a defect of vision that is caused due to regular weak and tear. It causes the blurring of the eye lens and is one of the main reasons for the loss of vision in people 40 and older. It is also the principle cause of blindness. Therefore, it is advised to treat it via surgery once diagnosed. Some common symptoms include blurring of vision, or maturing cataract.

Persistence of Vision

Our eyes work just like a camera. When we look at something, the sensation of us looking at it lasts for a period of 1/16^th seconds. This phenomenon is called the persistence of vision. This is used in various ways and one of the more prominent ones is animations. Images are drawn on pieces of paper called frames. These frames are flashed on the screen for a very short period of time and then replaced by another frame. This creates the optical illusion that the images are moving.

Care of Eyes

Our eyes are one of the most essential organs. However, most of us oversee their importance until an ailment gets created that defects our vision. So, to avoid this we must take good care of our eyes. Here are some ways we can take care of them:

·         Eat A Vitamin A Rich Diet – Eating a Diet Rich in Vitamin A which includes fish, eggs, milk, fresh fruits, etc can replenish our eyes with nutrients. The deficiency of vitamin A causes night blindness which does not allow us to see in low light conditions.

·         Wash Eyes 2 – 3 times a day with cold water.

·         If something enters the eye, do not run it, wash it instead.

·         If you face twitching, itching, dryness, or redness in the eye, visit an eye specialist.

Special Care for Visually Impaired People

A visually impaired person is a person who is visually impaired to such a degree that they require assistance to perform their day to day activities. Visual Defects such as Hypermetropia or Myopia can be treated by the use of special lenses, cataract can be treated via surgery unless it is of such extent that the person is blind. To aid these people, a lot of aids have been created. A few of which are:

·         Auditory Aids – Auditory Aids Such as Cassettes and CD’s allow people to get an understanding of their surroundings.

·         Olfactory Aids – Olfactory Aids use Unique smells to give visually impaired people a sense of their surroundings.

·         Tactual Aids – Tactual Aids are aids such as a blind stick or braille dots that allow the visually impaired to navigate their surroundings.

·         Electronic Aids – Electronic Aids are devices that help the visually impaired learn about their surroundings.

Braille

The Visually impaired read using a special language known as braille. This language consists of rectangular cells being printed on thick papers with dots in specific orders to indicate letters, groups of letters, or numbers. Each rectangular cell consists of 6 dots, or two columns with three dots each. The way these dots are placed can make 63 combinations.

Luis Braille

Luis Braille is the creator of the modern braille language. He was born in France in 1809 and went blind at the age of three due to an accident at his dad’s bard. This infection caused him to completely lose his sight. His parent sent him to a normal school in which instead of reading and writing braille relied on his sense of memory. In 1819, he received a full scholarship to  France’s school for the blind youth and began to develop a system that would allow him to read. He utilized signals used by soldiers to communicate in the dark to work on his language. By the Age of 20 he had perfected this language and 2 years after his death in 1852, it was officially adopted as the official language for the blind.

Metals and Non Metals

Metals, Non – Metals, and Metalloids

Metals are used extensively in our day to day life. From being used in Automobiles, to pen tips, bikes, rims, houses, etc they are used for a lot of things. Around 80% of the elements discovered by us are metals. Metals are usually hard and shiny. They are also found in a combined state. For example, Calcium in Limestone ( Calcium Carbonate ), or Sodium in Rock Salt ( Sodium Chloride ). However, they can also be found in a free state such as gold or silver. Non – Metals are usually Dull and Soft. For example, Oxygen, carbon, etc. Some elements show properties of both metals and non – metals. They are known as metalloids. For example, arsenic, silicon, etc.

Physical Properties of Metals and Non – Metals

Let’s Learn more about the physical properties of Metals and Non – Metals:

·         Physical State –

o   Metals are Usually solid at room temperature. There are exceptions of metals such as mercury and gallium which are liquid at room temperature.

o   Non – Metals exist in all states at room temperature. For example, phosphorus, sulphur, iodine, etc are solid at room temperature, while oxygen, nitrogen, etc are gaseous at room temperature, etc.

·         Malleability – Malleability is defined as the ability of a substance to be beaten into thin sheets.

o   Metals are malleable. Gold and silver are the most malleable metals. This is why they are often used to make ornaments. Aluminum is also an example of a malleable metal and is used to wrap foods. Gold can be beaten so thing that it turn translucent while still being intact.

o   Non Metals are non – malleable and break upon beating due to their brittle – ness.

·         Ductility – Ductility is the Ability of a substance to be coiled into thin wires.

o   Metals are ductile. However, their ductility may vary. Gold and Silver are the most ductile metals. However, tin is not so ductile but can still be made into a wire. Copper and Aluminum are also quite ductile and are hence used to make wires.

o   Non – Metals are not ductile and are brittle.

·         Luster – Luster means Shine.

o   Most metals are lustrous. Metals such as Gold, Copper, and Silver are highly lustrous while metals such as magnesium and aluminum are dull but regain luster upon rubbing with sand paper.

o   Non – Metals are not lustrous. However, there are exceptions. Iodine and Graphite as two lustrous non – metals.

o   Why do some metals become dull but regain their luster upon rubbing? – Metals react with substances in the air such as oxygen, carbon dioxide, and moisture to form oxides, carbonates, and hydroxides on their surface. Upon rubbing, this layer of metal goes away exposing the shiny metal making it appear lustrous again. Metals Such as silver obtain a black coating called silver Sulphide while copper obtains a greenish coating of copper carbonate.

·         Hardness –

o   Metals are usually hard except for exceptions such as sodium, calcium, and phosphorus. Otherwise, most metals are resistant to cuts, scratches, and grinding. Sodium can even be cut with a knife.

o   Non – Metals are usually Soft except for exceptions such as the diamond. The Diamond is the hardest known substance to the human race. That is why it is used in cutting machines.

·         Tensile Strength – The Tensile Strength of a Substance is its resistance to pulls.

o   Metals have a high tensile strength which is why they are used in construction.

o   Non – Metals have a low tensile strength and can be broken easily.

·         Density –

o   Most metals have a high density while exceptions such as sodium and potassium exist.

o   Non Metals have a low density.

·         Sonority – Sonority is a Substances ability to produce a ringing sound when struck.

o   Metals are sonorous and produce unique sounds therefore being used in bells.

o   Non – Metals are not sonorous and do not produce a ringing sound.

·         Conductivity –

o   All Metals are conductors of heat and electricity. Some better, some worse. Silver is the best conductor while lead is the worst. Metals such as aluminum and copper are moderate therefore are used to produce wires and cooking utensils. Iron and Mercury both offer great resistance to electricity,

o   Non Metals are bad conductors of heat and electricity. Graphite, however, is an exception which is why it is used as electrodes in electrolysis.

·         Melting and boiling Points – The Melting point is the temperature at which a solid substance turns into a liquid, While the boiling point is the temperature at which a liquid turns into a gas.

o   Metals Usually Have a high melting a boiling point with tungsten have the highest at 3410 degrees Celsius. However, some metals have a moderate burning point. Gallium has the lowest melting point of 30 degrees Celsius.

o   Non – Metals usually have a low melting and boiling point with exceptions such as diamond, boron, etc.

Chemical Properties of Metals and Non – Metals

Properties that describe how a substance changes upon undergoing certain reactions are known as chemical properties. The Reactivity of these substances with other substances or even themselves is a substances reactivity.

·         Reaction With Oxygen –

o   Metals –

à Metals Such as Potassium and Sodium react with oxygen at room temperature.

à Metals Such as Magnesium and Zinc React with oxygen upon heating.

à Iron and Copper do not react with oxygen even upon strong heating. They only React upon prolonged heating.

à Most Metalloids Formed during these reactions are basic in nature. They dissolve into water to form bases ( alkali ). They will turn red litmus blue which verifies this. However, Aluminum oxide, zinc oxide, etc display properties of both acids and bases and are called amphoteric oxides.

o   Non – Metals –

à Carbon Reacts with oxygen upon prolonged heating.

à Sulphur Reacts oxygen easily with a flame.

·         Reaction with Water –

o   Metals –

à Potassium and Sodium metals react with cold water to form their respective hydroxides and Hydrogen.

à Magnesium Reacts with hot water to form magnesium oxide.

à Zinc and Iron React with steam to form their respective oxides and hydrogen.

o   Non – Metals –

à Non – Metals generally don’t react with water. This is important as it is what allows underwater life to exist. If non - metals reacted with water or steam, oxygen in water would not exist therefore killing all marine life.

Corrosion of Metals

You would have observed that some objects get a thin layer of deposition on top of them. For example, the brownish layer of iron, the green layer of copper, etc. This layer is caused due to a chemical reaction between the surface of the substance and the moisture and oxygen present in the air. This Reaction is called Corrosion. The corrosion of iron is called rusting. Metals react with dilute acids to form salts and hydrogen gas. Non – Metals do not react with dilute acids to give hydrogen gas.

Reactivity of Metals

The reactivity of metals is a list in descending order ( most reactive à Least Reactive ). This makes it simpler to understand which metals can displace which in a displacement reaction. Hydrogen, a non – metal is put in this list as it also forms positive ions upon electrolysis.

Uses of Some Metals

Metals are very important in our life. Below are Some uses of Metals:

·         Iron is Used to make steel which is used in construction due to its high tensile strength.

·         Aluminum and Copper are Used to Make Wires and Utensils due to their high conductivity.

·         Copper is Also Used to make statues and decorative pieces of art.

·         Gold and Silver are Used to make Jewelry and Ornaments.

·         Magnesium Hydroxide is used as an Antacid

·         Metals like titanium are used for a countries economy and for space exploration.

·         Some metals are used to make nuclear weapons.

Uses of Some Non – Metals

Non – Metal Substances are also important to our life. Some of which, we require to survive. Here are some uses of non – metals:

·         Oxygen is utilized by almost every living organism and is required to sustain life.

·         Nitrogen and Phosphorus are used to make fertilizers.

·         Sulphur is used to make fire crackers.

·         Coal is used to sustain fires.

·         Phosphorus is used to make match sticks.

·         A dilute solution of iodine is used as an antiseptic for wounds.

·         Chlorine and Ozone are used as Germicides

Alloys

Alloys are a combination of or mixture of two or more metals. There are alloys that also include non – metals such as carbon. Alloys are done to make metals harder or to alter / obtain new characteristics. Steel is an alloy of iron, chromium, and / or nickel. The small amounts of chromium and nickel make the iron rust less. Carbon is also added to make it harder. The Composition of an alloy may be altered to fit certain requirements. Let’s go deeper into the composition of 5 of the most common alloys: