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Ionic Bonding | IGCSE Chemistry (0620) | Best Notes

2021-05-05T22:14:00.001+05:00

Ionic bonding is an important topic in IGCSE Chemistry. Therefore, you should be familiar with some of its important concepts.

So if you want to know about cations, anions and ionic bonds, stay tuned. Now, let's start the topic without further introductions.

What is an Ion?

An ion is a particle with an electric charge (either positive or negative). If a particle gains electrons (like non-metals), then it will have a negative charge.

On the other hand, if a particle loses electrons (like metals), it will have a positive charge. Now moving on to the question I asked you earlier about cations and anions.

Remember that cations are positively charged ions (which means that they lose electrons). Apart, the anions are negatively charged ions (which means that they gain electrons).

Note: The electronic structure of an ion will be similar to that of a noble gas (for example neon, argon and helium).

Now, let's dig a little bit deeper into the topic to discover new concepts as well.

Ionic Bonding Notes:

Metals: When we are talking about metals (such as calcium and potassium), remember that they will lose electrons to achieve an electronic structure that of a noble gas.

What do I mean by that?

Let me explain.

Noble gases are gases that have either two or eight electrons in their outermost shell. This means that they are stable. Thus, they do not lose or gain electrons to become stable.

When it comes to metals, they lose electrons to become stable. Or in other words, they achieve the same state as noble gases have (stable or unreactive).

This is the reason why I referred to their structure as similar to noble gases. I hope this makes sense to you as well now.

Non-metals: They always gain electrons to achieve the electronic configuration of that of a noble gas (become stable). This is the reason why they are negatively charged (because they gain electrons).

Note: The force of attraction between the positive and negative charges (that hold them together) is known as the electrostatic force.

Now, let me tell you about how ionic bonds are formed and how can we deduce their formula?

How ionic bonds are formed?

Let's take an example to understand how the formation of ionic bonds take place.

Lithium Chloride (LiCl)

Lithium is an alkali metal (in group 1 of the periodic table). Its electronic configuration is 2, 1. This means that it has to lose one electron to become stable.

Moving on to chlorine, its electronic configuration is 2, 8, 7. This means that chlorine needs only one electron to become stable.

So what happens is that both of these elements form an ionic bond (lithium loses an only electron and chlorine gains one electron) to become stable.

Note: An ionic bond is formed between a metal and a non-metal. For example, sodium chloride (NaCl) is formed between a metal (sodium) and a non-metal (chlorine).

More Resources:

Speed of Reaction Notes

The atmosphere and environment | O Level Notes (5070)

To deduce the formula of an ionic compound, follow the steps mentioned below.

Find out the ions in the compound (in this case lithium and chlorine ion)

Then, write down the ions (for example Li+ and Cl-)

Finally, cross multiply their powers (value on the ions) to find out the formula.

Now moving on, let's talk about the properties of ionic compounds.

Properties of Ionic Compounds:

They have high melting and boiling point.

The ionic compounds have a high melting and boiling point because the electrostatic forces between the positive and negative charges and very difficult to overcome.

Therefore, high heat is required to break the strong bonds. As a result, they have a high melting and boiling point.

They conduct electricity in the molten and aqueous state:

In solid-state, they do not have any free moving (mobile) ions or electrons to conduct electricity (by moving around the structure). However, they have free moving ions or electrons in a molten or aqueous state.

These ions allow ionic bonds to conduct electricity by freely moving around the structure.

They are soluble in water and insoluble in organic compounds (Higher):

Most ionic compounds are soluble in water because water molecules strongly attract the charged ions. Therefore, they dissociate in water and become solvated.

This is the reason why ionic compounds are soluble in water.

On the other hands, they are insoluble in organic solvents because the organic solvents are non-polar. In simple words, they cannot break or dissolve the ionic compounds.

Conclusion:

Thank you very much for reading this article about ionic bonds. If you have any questions, do leave them below. I will try my best to answer them.

To recap, we discussed ions (cations and anions), the formation of ionic bonds, how to find out the formula of ionic bonds, and their properties.

This information may be useful for IGCSE Chemistry and GCE O Level Chemistry students. Stay tuned for further useful resources.

Homeostasis | GCE O Level Biology Notes (5090)

2021-01-05T23:54:00.001+05:00

Homeostasis is a very important topic in biology (5090) and there are multiple concepts in this topic which you need to learn.

First of all, you should know that what is meant by homeostasis?

The system of a body which is responsible for the maintenance of the internal environment is known as homeostasis.

In other words, it is the ability to maintain a stable state that continues despite the changes outside. This system ensures the survival of all species from plants to animals.

This was all about the introduction of this topic. Now, let's move into further details and learn about some other topic as well.

Negative feedback:

To maintain a constant internal environment, a significant principle known as negative feedback occurs. In other words, it is the principle on which homeostasis works.

In biological systems, negative feedback (a regulatory mechanism) is a type of regulation that occurs when a specific stimulus (change) is detected.

For instance, when the temperature of your body will rise, the body will bring about specific actions in order to reduce the temperature. This opposite change is known as negative feedback.

Some of the examples of negative feedback are listed below:

Thermoregulation (a mechanism to restore the body temperature when it changes).

The maintenance of blood glucose level (insulin to reduce it and glucagon to increase the glucose level).

Osmoregulation (to retain the water potential of the body).

We will discuss all these examples in detail in this article.

Now you might be wondering, how does negative feedback occur? Let me tell you.

Firstly, any change (stimulus) occurs. Secondly, the receptor in the body detects this change. When the change is detected, a mechanism to correct that change occurs.

In this way, negative feedback (an opposite effect to the change) occurs.

Examples of homeostasis:

Osmoregulation:

Osmoregulation refers to the mechanism in the body that maintains the water potential. The body brings about the opposite change to the stimulus to restore the normal condition.

When the water potential increases (than normal), less ADH (anti-diuretic hormone) is secreted so that less water is absorbed by the body.

Moreover, more water is excreted through the urine and the kidney also absorbs less water.

These opposite changes lower the water potential and as a result, the water potential is restored back to normal. In short, when the water potential rises, the body will reduce the water potential to restore normal conditions.

However, when the water potential in the body decreases, more ADH is secreted so that more water is absorbed by the body and kidneys.

Similarly, less urine is produced to secrete less water and the urine becomes concentrated (because it contains less water). The negative feedback increases the water potential.

As a result, a normal condition is brought about. This is how the water potential of a body is regulated.

Now, you should also know how the glucose level of your body is maintained. So, let's discuss the topic in detail now.

Regulation of blood glucose concentration:

In order to maintain normal glucose concentration in the blood plasma, our body is responsible for certain actions depending upon the concentration of glucose.

For example, when the glucose concentration increases after a meal, the pancreases detect the stimulus (because they act as a receptor) in this case.

Therefore, the pancreas secretes insulin in the bloodstream to decrease blood glucose concentration.

Insulin enters the liver where it converts glucose to glycogen to be stored in the liver. In this way, the glucose concentration is reduced so that normal conditions prevail.

Further reading:

Enzymes notes | GCE O Level Biology (5090)

Drugs notes | GCE O Level and IGCSE

The atmosphere and environment

However, when the glucose concentration decreases, pancreases (acting as a receptor) releases glucagon which enters the liver through the bloodstream.

Glucagon converts the stored glycogen to glucose which enters the bloodstream to increase glucose concentration back to normal. This is how negative feedback maintains the glucose concentration in our body.

When the body is unable to maintain the blood glucose concentration, a disease known as diabetes occurs. In type 1 diabetes, the insulin-secreting cells are unable to produce insulin.

As a result, the glucose concentration in the body remains high and the presence of glucose in urine indicates diabetes because the urine of a healthy person will never contain glucose.

This can be treated by injecting insulin which converts glucose to glycogen in the body which is stored in the liver. Some of the symptoms of glucose are:

Blurred vision
Weakness or tiredness
Extreme thirst
Weight loss
Loss of consciousness

The people with type 1 diabetes can perform regular exercise to maintain their glucose concentration because glucose level is reduced during exercise as it is used for respiration.

These were some key concepts which you should know about the maintenance of glucose concentration in your body.

Skin and thermoregulation:

Skin is the largest organ of the body and it helps us to maintain the body temperature, protect us from microbes and elements and permits us to feel sensations like hot and cold.

The skin has multiple layers such as:

Epidermis

Dermis

Subcutaneous fat

The epidermis is the part of the skin you see (the top layer of the skin). The epidermis consists of a cornified layer (which prevents germs from entering the body), a granular layer (containing living cells) and a Malpighian layer (which provides skin with its colour).

The dermis is another thick layer, underneath the epidermis, and it has hair follicles (from where the hairs emerge) which cause goosebumps to occur.

During cold, the erector muscles contract causing the hairs to erect which allows them to trap air. In this way, heat is trapped inside the hairs which raise the body temperature during cold (an example of homeostasis).

Blood capillaries are also present inside the dermis and they also play a very important part in maintaining the body temperature.

When the arterioles dilate (during hotter conditions), more blood flows through them (to lose some heat to cool the body). However, when they contract (during cold), less blood flows through them.

Apart, the sebaceous gland in the skin is responsible for secreting sebum (an oily substance) which keeps the hair smooth, soft and even lubricates them.

It also prevents the entry of pathogens (such as bacteria) to the body. The nerve endings in the skin also play an important role in detecting the changes in temperature in the body.

Lastly, the sweat gland is responsible for producing sweat. When the temperature of the body rises, heat from the body is lost through sweat.

However, less sweat is produced during the cold in order to maintain heat during cold. The actions of the body during hot and cold are summarised below.

During summers (hotter conditions):

Blood vessels dilate (vasodilation)

Sweat gland produces more sweat

The metabolic rate decreases

Heat is lost through urine, faeces and expired (exhaled) air

During winters (colder conditions):

Blood vessels constrict (lesser blood flows to prevent heat loss)

Shivering occurs to increase body temperature

The metabolic rate increases the generate more heat

The sweat glands become less active (to prevent heat loss)

Conclusion:

With this, our article about homeostasis has come to an end. I hope that all your questions have been answered through this article.

The topics covered in this article are listed below for your reference:

What is meant by homeostasis?
What is negative feedback?
Osmoregulation (maintenance of water potential)
Maintainance of blood glucose concentration
Diabetes
Skin
Thermoregulation (maintenance of temperature)

Thank you very much for reading till the end and stay tuned for more.

Turning Effect of Forces | GCE O Level Physics (5054)

2021-01-02T00:53:00.004+05:00

The turning effect of forces is a very important topic in Physics and there are multiple topics in this chapter which you need to learn.

First of all, you should know that a force may cause an object to rotate (clockwise or anticlockwise) around its pivot (a central point or shaft where an object turns).

This is known as the turning effect of a force or the moment of the force.

The turning effect of a force is mainly dependent upon two factors which are:

The magnitude of the force
The perpendicular distance from the pivot to the line of action of the force

The moment of a force (torque):

The torque (moment of a force) is the product of the force and the perpendicular distance from the line of action of the force to the pivot (central point).

In terms of an equation, this can be summed up as:

moment of a force = force (F) x distance (d)

M = F x d

The SI unit for torque (moment of a force) is newton metre (N m) because the symbol for force is newton and the symbol of distance is metre.

Note: The distance taken from the pivot to the line of action of the force will always be perpendicular.

There are multiple applications of turning effect in our daily life and some of them are mentioned below.

Examples of turning effect:

The force applied by a worker to a spanner to rotate a nut.

A person pushing a swing and making it rotate around its pivot.

A force applied to a door-knob (making it swing around its hinge).

A driver turning a steering wheel by applying a force on its rim.

A person removing a bottle's cork by pushing down the bottle opener's lever.

These are some of the daily life applications of turning effect of a force.

Principle of moments:

According to the principle of moments, when a body is in equilibrium (balanced state), the sum of the anticlockwise moment about a pivot is equal to the sum of the clockwise moment about the same pivot.

In other words, you can say that torque 1 is equal to the torque 2 and in terms of formula, it can be said:

anticlockwise moment = clockwise moment

F1 x d1 = F2 x d2

Note: When an object is at equilibrium, the resultant force on the object is zero and the resultant moment on the object is also zero.

To ace this concept, you need to practice some questions which are listed below.

Question 1:

A uniform rod AB of length 2 m has a weight of 100 N carries a load of 20 kg as shown in the diagram below. It is supported by two strings at its end. Determine the tension in the strings.

Solution:

Let the tension of the string at A be T1

Let tension of the string at B be T2

The moment at A = F x d

100 x 1 + 200 x 0.5 = T2 x 2

T2 = 100 N

By applying the principle of the moment:

Sum of upward forces = sum of downward forces

T1 + T2 = 200 + 100 = 300 N (total force)

T1 = 300 - 100 = 200 N

Question 2:

A uniform rule is balanced about a pivot at its midpoint when a 10 N weight is suspended from the 20 cm mark. One more weight of 8 N is suspended from another position (X).

Find the torque (moment) of the 10 N weight about the pivot and the position (X) from where the 8 N weight is suspended.

Solution:

We will solve this question in two parts. Firstly, we will calculate the moment around the 10 N force.

moment = F x d

moment = 10 x 0.30 (because 30 cm is 0.30 m)

moment = 3 N m

To find the unknown distance, we will apply the principle of the moment.

Let the unknown distance be d1;

clockwise moment = anticlockwise moment

8 x d1 = 10 x 0.30

d1 = 0.375 m

Position X = 0.50 - unknown distance = 0.50 - 0.375

Posiotion X = 0.875 m

Centre of gravity:

The centre of gravity (CG) of an object is when all sides are in balance and is the point at which the weight is equally dispersed.

Further reading:

Electromagnetic waves notes (5054)

Mass, weight and density notes

Speed of reaction notes (5070)

In simple words, this is the point through which the weight of the whole body appears to act.

The objects which have a uniform density and regular shape (such as triangles, circles, cuboids, rectangles and spheres) have their centre of gravity at their geometric centre.

However, the centre of gravity of an irregular object is not its centre.

You can calculate it by following the procedure mentioned below:

Draw a line on the object along the string.

Use another point on the object to draw one more line.

Now, you will have two lines that will intersect (cut) each other.

The point of intersection will indicate the centre of gravity.

This method can be used to determine the centre of gravity of irregularly shaped objects since they are difficult to balance. You can also draw a third line in order to increase the accuracy of the experiment.

Stability:

Stability refers to the ability of an object to return to its original static equilibrium (or the original position) after it is displaced.

In order to understand stability, you should know some types of equilibrium.

Stable equilibrium: When small externally induced displacements produce torques or forces that oppose the displacement allowing the body to return to its original equilibrium.

For instance, a brick lying on a level plain and a hanging pendulum (suspended freely).

In other words, the centre of gravity rises and returns to its original position as well.

Neutral equilibrium: When externally produced small displacements do not produce any unbalanced forces (torques) that oppose the displacement allowing the body to remain in its new equilibrium.

In simple words, the centre of gravity remains at the same height. For instance, a football lying on a plane (level) surface.

Unstable equilibrium: When the centre of gravity drops because the forces (torques) add to the displacement.

You should also know that the centre of gravity is dependent upon:

Low centre of gravity
Wider base area

This means that if the centre of gravity is kept as low as possible, the object will be more stable (the concept is applied to the racing cars).

Stability increases with a wider base area.

Similarly, if the height is increased and the base area is kept wider, the stability also increases.

Conclusion:

With this, the topic of turning effect of forces has come to an end. I hope that all your queries have been addressed.

You should practise past paper questions from this topic because it is a very important topic from examination point of view. The topics covered in this article are listed below for your guidance.

Moment of a force (torque)
Principle of moments
Centre of gravity
Types of equilibrium
Stability

Thank you very much for reading and staying with me till the end and stay tuned for more.

Speed of Reaction | GCE O Level Chemistry Notes (5070)

2020-12-31T23:52:00.001+05:00

Speed of reaction is a very important topic in Chemistry and there are multiple concepts with which you should know to ace your exams.

Rate of reaction refers to the speed at which a chemical reaction proceeds (takes place) and this speed can vary dramatically.

The speed at which a chemical reaction takes place is mainly dependent upon two factors. Those are:

Frequency of collisions:

The more often molecules collide with each other, the greater the rate of reaction.

The energy of collisions:

When the molecules strike each other with greater energy, the reaction proceeds faster. In other words, the forcefully the molecules collide, the greater will be the rate of reaction.

This was all about the introduction of this topic. Now, let's discuss some important concepts about this topic.

How do we measure the speed of a reaction:

To know the rate at which the reactants are utilised or the rate at which the products are formed, we can measure the time taken for the reaction to complete.

Note: If the reaction is faster, it will take less time to complete. However, if the reaction is slower, it will take more time to proceed.

To find the speed at which a reaction takes place, you can:

Measure the change in mass
Measure the amount of gas released

Let us design an experiment on how you can measure the change in mass and find the rate (speed) of reaction.

Measuring the change in mass:

Set up the apparatus as shown below.

Firstly, place a conical flask on an electronic balance.

Secondly, add hydrochloric acid (HCl) and marble (calcium carbonate).

Place cotton wool at the top of the conical flask to close it so that the gas (carbon dioxide) does not escape. This is the time when you should note the initial mass of the contents.

Start a stopwatch as soon as the acid and marble start reacting.

Note down the mass at different internals (for example measure the mass after each minute).

Note the mass of the contents once the reaction is over and stop the stopwatch immediately.

Plot the graph of the change in mass (on Y-axis) against time (on X-axis). The gradient of the graph will represent the rate (speed) of reaction.

In the reaction mentioned above, the graph would look like:

This was one of the methods to find out the rate of a reaction. Now, let's take a look at another method to find the speed at which a reaction proceeds.

Measuring the amount of gas released:

In this method, you would require a conical flask, gas syringe, stopwatch and a stand.

Set up the apparatus as shown above.

Firstly, add dilute hydrochloric acid (HCl) to the conical flask containing calcium carbonate (marble).

Note: When an acid reacts with a carbonate, carbon dioxide gas is released.

Secondly, measure the amount of gas released after each minute. Then, plot the graph of the volume of gas produce (on Y-axis) against time (X-axis).

In the graph, the gradient will indicate the speed of the reaction (the larger the gradient, the higher the speed of a reaction).

Initially, the gradient of the graph will increase but as the reaction proceeds, the gradient decreases. There will be a time when the graph will show a horizontal line which would indicate that the gradient is zero.

This is because, after a certain period, no more carbon dioxide will be produced.

These are the two methods which you can use to calculate the speed of reaction. Now, you should also know some of the factors that affect the rate of a reaction.

Factors affecting the rate of a reaction:

Size of the reactant:

The smaller the size of a particle, the higher the rate at which a reaction would proceed. Why is this so?

This is because the particles with smaller size have a larger surface area (the exposed area).

Similarly, larger surface area means more effective collisions and therefore, the speed would also increase.

However, if the size of a particle is bigger, the rate (speed) of reaction would be lesser because the surface area would also be less. This will be because the collisions would also decrease.

Further reading:

The atmosphere and environment notes (5070)

Electromagnetic waves | GCE O Level Physics

In order to put this information into an experiment, add some marble to dilute hydrochloric acid and calculate the amount (volume) of carbon dioxide produced.

Note that everything in the experiment (such as temperature and amount of acid) should be kept constant. The size of the marble should only be varied.

You will conclude that when the size of a marble is smaller, the amount of carbon dioxide produced will be greater. Now, what do you think would be the effect of pressure? Let me tell.

The pressure:

When the pressure is increased, the speed of reaction would also increase because there will be more effective collisions.

When the particles will collide more frequently, the reaction would proceed faster. You can increase the pressure by decreasing the volume because the particles will get closer to each other.

But, if you decrease the pressure, the speed would decrease because there will be less effective collisions.

When the particles will collide less frequently, the reaction would proceed slower. It is to note that when you decrease the pressure, the concentration of the gas also decreases.

The concentration of the reactant:

Increasing the concentration would increase the rate of reaction because the particles (reactants) will collide more frequently (effective collision).

This is because higher concentration refers to an increase in the number of particles. As a result, more particles would collide and the reaction would occur rapidly.

If the concentration is less, the reaction rate will decrease because there will be lesser collisions between the particles. The diagram below illustrates what is meant by higher and lower concentration.

The temperature:

If you increase the temperature, the reaction speed would also increase.

Increasing the temperature raises the average kinetic energy (related to motion) of the reactant particles. As a result, the particles move at a faster rate and collide more frequently.

These effective collisions cause the reaction to proceed faster.

However, decreasing the temperature also decreases the rate of reaction because the number of collisions reduces when the average kinetic energy reduces.

In short, temperature and reaction rate are directly related (when one increases, the other also increases and vice versa).

The use of catalysts:

A catalyst is a substance that increases the rate at which a reaction proceeds but remains unchanged at the end of a reaction.

In other words, a catalyst remains unconsumed during a reaction. Enzymes are the catalysts made up from protein and they speed up biochemical reactions.

How do catalysts increase the speed of a reaction?

Catalysts lower the activation energy (the energy required for a reaction to proceed) for a reaction. You can also say that a catalyst changed the reaction mechanism.

Moreover, lowering the activation energy means that bonds are broken down more rapidly and therefore, effective collisions also occur. You should know that catalysts only speed up a reaction but they do not affect the amount (volume) in a reaction.

For example, we use Iron as a catalyst in the Haber's process (production of ammonia) and Vanadium pentaoxide (V2O5) as a catalyst in the contact process (for the production of sulphuric acid).

These are some of the factors that affect the rate of a reaction.

Conclusion:

With this, this article about the speed of reaction has come to an end. I hope that all your questions have been answered. Practice plenty of past paper questions to ace this topic.

Some of the topics that are covered are listed below for your guidance.

How to calculate the speed of a reaction?

The affect of temperature, pressure, concentration and catalyst on the rate of reaction.

How does the particle size influence the rate (speed) of a reaction?

Thank you very much for reading and staying with me till the end.

Electromagnetic Waves | GCE O Level Physics Notes (5054)

2020-12-27T20:37:00.001+05:00

What do we mean by electromagnetic (EM) waves?

The electromagnetic waves (also known as EM waves) are formed as a result of the vibrations between the electric field and magnetic field.

In simple words, these are the waves of the electromagnetic field which make up a family of waves known as the electromagnetic spectrum.

The EM waves, such as radio, micro, ultraviolet and X-rays, propagate through space carrying electromagnetic radiant energy.

Let me further explain this with the help of an example. The light from a lamp in your house is a type of electromagnetic radiation. Similarly, the waves travelling from the radio station are also a type of electromagnetic radiation.

In the electromagnetic spectrum (refers to the range of frequencies of the electromagnetic radiations in order with their respective wavelengths), the EM waves are arranged in order of their frequencies and wavelengths.

Radio wave (which have the longest wavelength and the lowest frequency) is the first in the electromagnetic spectrum while gamma rays (which have the shortest wavelength and highest frequency) are the last.

Note: Gamma rays have the highest energy in the electromagnetic waves because they have the greatest frequency.

The EM waves are mentioned below in respect to their frequencies and wavelengths.

Radio waves (greatest wavelength, lowest frequency)
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays (greatest frequency, lowest wavelength)

You can use the following mnemonic (a pattern of words which assists in learning something) to learn the order of these waves:

Red Monkeys In Vans Use X-ray Guns

This takes us to another very important topic which is about the properties of electromagnetic waves, so let's discuss that topic in detail now.

Properties of EM waves:

They carry no electric charge

This is because the EM waves are neutral in nature.

They do not require a medium to propagate

This means that these waves travel through the vacuum because they are very powerful.

EM waves are transverse waves (waves that vibrate perpendicularly to the path of propagation)

This is because the magnetic and electric field oscillate at 90° to each other.

They travel at the same speed of 3x10^8 m/s (speed of light) in a vacuum and transfer energy from one place to another

Electromagnetic waves obey the laws of reflection and refraction

When EM waves move from one medium to the other (for example from glass to air), their speed and wavelength change

However, their frequency remains unchanged in all mediums.

You should also know that mathematically, we can calculate the speed of the EM waves with the help of a formula.

The formula says:

v = f x λ (where v = wave speed, f = frequency of the wave and λ = wavelength of the wave).

Visible spectrum:

Colour is a quality of light and light has properties in common with particles and waves.

Moreover, the beans of light have different values of frequency (number of waves passing through a fixed point in one second) and wavelength.

You should know that in the colour spectrum, red has the smallest frequency and the longest wavelength while violet has the highest frequency and the shortest wavelength.

Red (shortest frequency, longest wavelength)
Orange
Yellow
Green
Blue
Indigo
Violet (longest frequency, shortest wavelength).

You should also know about the application of electromagnetic waves in practical life. So, let's discuss the topic.

Application of electromagnetic waves:

Radio Waves:

They are used in the standard broadcast radio, air-traffic control, television, remote-controlled toys and for navigation as well.

Since radio waves have the longest wavelength, they can travel over obstacles, such as mountains). Different frequencies of radio have variable propagation characteristics.

They can produce high voltage AC transmission lines and can transmit power over long distances.

The radio waves with longer wavelength are also used for submarine communication and waves with shorter wavelength are used as FM (frequency modulation) radio.

Ultraviolet rays:

Ultraviolet radiations are used in medical, dental and industrial processes for multiple purposes such as killing bacteria, curing resins and inks and suntanning.

You can also say that UV (ultraviolet) radiations are used in sunbeds for tanning. This use is controversial because constant exposure to UV rays can lead to skin cancer.

UV rays have the ability to inactivate viruses and bacteria and therefore, they are used for sterilizing equipment (medical and laboratory).

Furthermore, these rays are also used in "curing". One example is the hardening of glues by this process.

Microwaves:

Microwaves are extensively used in modern technology.

For instance, they are used in wireless networks, spacecraft communication, radar satellite and for cancer treatment as well.

Moreover, these waves are also used in microwave ovens as a source of transferring energy. They heat the food by penetrating into it and as a result, water molecules vibrate vigorously to produce heat.

Mobile phones, speed cameras, aircraft, ships and weather forecasters also use microwaves.

Microwaves are also used in carrying signals to and from satellites for the global positioning system (GPS). This is because they can penetrate through the atmosphere and pass light, haze, snow and rain as well.

There are plenty of other uses of microwaves as well but some of the prominent ones are mentioned above.

Visible light:

We use visible light images to predict the weather by watching clouds. In short, visible light has multiple uses in terms of "sight".

Apart, visible light is also used for making lasers for multiple purposes such as for surgery. These waves also make our television, mobile phone screens and computer.

Visible light is also used in optical fibres for telecommunications and medical purposes.

Infrared radiation:

These waves are used in detecting heat loss in insulated systems, detecting overheating of electrical apparatus and are also utilised for studying blood flow in the skin.

In terms of military, these are used for surveillance, tracking homing and target acquisition.

Apart, the infrared remote controllers are utilised for controlling multiple electrical devices such as television and air conditioner. The temperature of the human body can also be detected by measuring the number of infrared radiations emitted by our body.

These waves are also used by electrical heaters, cookers, optic fibres and thermal imaging cameras (to detect people in the dark) but these radiations can cause burns to the skin.

X-rays:

X-rays are the high-frequency (and can penetrate through the human body) waves and are used to kill cancer cells in radiation therapy.

They are also used to detect and diagnose a bone fracture, infections, some tumours, dental issues and bone loss as well.

In terms of security, they play an important part in detecting equipment in the bags and are also used to check tiny flaws in heavy metal equipment.

X-rays are also used in detecting digestive problems, blood vessels blockage and heart problems such as congestive heart failure.

Gamma rays:

Gamma rays are used in medicine (radiotherapy) and industry (sterilization and disinfection).

They have high penetration power and therefore, they are used for treating brain tumours to kill cancer cells.

Gamma rays are also used in detecting minerals underground and they can bring about significant biochemical changes in the living cells (making them suitable for radiation therapies).

Therefore, exposure to these ionizing radiations can cause cancer.

These are some of the application of the electromagnetic waves which you should be familiar with.

Conclusion:

With this, the article about electromagnetic waves has come to an end. I hope that all your queries have been answered.

The topics covered in this article are listed below for your reference.

Electromagnetic waves
Visible spectrum
Application of electromagnetic waves

Thank you very much for reading.

Atmosphere and Environment | GCE O Level Notes (5070)

2020-12-18T20:42:00.002+05:00

The atmosphere and environment is a very important topic in GCE O level Chemistry (5070). There are multiple concepts in this chapter that need to be addressed.

Therefore, let's dive into the topic without further introductions and start from the very beginning of this chapter.

What is the atmosphere?

Our earth is surrounded by a layer or layers of gases known as the atmosphere.

In other words, atmosphere refers to the layer of air that is held by gravity. You should know that without the atmosphere, there would be no life on earth.

But, why is that so? Let me explain that in detail.

The atmosphere is a protective layer that serves as a shield to the earth and protects it from the harmful radiations from the sun. This action ensures that an optimum temperature is maintained on earth.

In other words, due to the atmosphere, the climate of the earth is moderate and it is a major reason why life exists on the earth.

We discussed earlier that the earth's atmosphere is made of air. Now you might be wondering, what does air consists of?

Similarly, you can also say that what is the composition of the atmosphere? Let me answer your question.

The composition of air:

You should know that the air is a mixture of multiple gases and it comprises of useful elements and compound.

The air comprises consists of:

Nitrogen: 78%
Oxygen: 21%
Carbon dioxide: 0.03%
Noble gases: 0.97%

Note: The planets in the solar system have a different atmosphere as compared to the earth. For instance, the atmosphere of Uranus consists mostly of hydrogen (83%).

At the same time, you should also be familiar with the concept of how do we separate air into its constituent gases?

How is air separated into its constituent gases?

Firstly, the air is cooled and compressed so that we obtain air in liquid form.

Liquid air is then separated into its fractions by fractional distillation (a process to separate fractions of a liquid, based upon the boiling point of the constituents).

Secondly, the liquid with the lowest boiling point is collected at the top of the fractionating column upon heating.

This is because the liquid with the lowest boiling point distils over first.

For example, when we conduct the fractional distillation of liquid air, Nitrogen is distilled first because it has the lowest boiling point (-196℃).

This takes us to another important topic in this chapter of the atmosphere and environment which is about air pollution.

Air pollution | Causes | Effects | Solutions:

The air we consume during breathing is not clean because it contains harmful chemicals.

In other words, when the air contains a very high concentration of chemicals that harm non-living and living organisms, we say that this condition is known as air pollution.

Many chemicals pollute our air such as sulfur dioxide, carbon monoxide, oxides of nitrogen and unburnt hydrocarbons.

Let's take a look at these chemicals in detail and learn how do they contribute to air pollution.

Sulfur dioxide and Carbon monoxide:

Coal, natural gas and petroleum (crude oil) are the fossil fuels that contain sulfur.

Therefore, when they are burnt (for example in industries), they produce sulfur dioxide. Similarly, the volcanic eruptions also release sulfur dioxide into the atmosphere.

Sulfur dioxide pollutes the air as this acidic gas can cause lung diseases, eye irritation, infections and coughing as well.

Likewise, inhaling this gas can cause irritation in the nose, eyes, throat and lungs which can lead to a sore throat and a burning sensation in the eyes.

On the other hand, Carbon monoxide is produced as a result of incomplete combustion of petrol in the car engines. This is an odourless (fragrance-free) and colourless gas.

Further reading:

Mass, weight and density | GCE O Level Notes

Waves Notes

Enzymes Notes

Carbon monoxide is very harmful to the body because it displaces oxygen from the blood. As a result, the vital organs of your body can be deprived of Oxygen.

It can lead to unconsciousness, breathing difficulties and even death in severe cases.

Oxides of nitrogen:

At high temperature, oxygen combines with nitrogen to form nitrogen oxide.

Similarly, when this gas (nitrogen monoxide) reacts with oxygen, nitrogen dioxide is produced.

Nitrogen dioxide forms acid rain when it reacts with water which can damage buildings and harm the aquatic life as well. Moreover, nitrogen dioxide can cause severe irritation in the eyes and lungs as well.

Unburnt hydrocarbons:

The chemical plants and exhaust fumes release unburnt hydrocarbons (that contain only hydrogen and carbon atoms).

When nitrogen dioxide reacts with the unburnt hydrocarbons, ozone is formed which can lead to smog.

As a result, crops can be damaged, lung diseases and infections can prevail and irritation in eyes and lungs can also occur.

Apart, methane (a colourless and odourless gas) is a greenhouse gas and it causes global warming. Moreover, this is released when animal and plant matter decay.

This takes us to another important topic which is about acid rain.

Acid rain:

When acidic gases such as nitrogen dioxide and sulfur dioxide react with water in the atmosphere, acid rain is formed.

You should know that nitric acid is formed when nitrogen dioxide reacts with oxygen and water.

nitrogen dioxide + water + oxygen → nitric acid

Similarly, when sulfur dioxide reacts with water sulfurous acid is formed which is oxidised into sulfuric acid.

The pH (the measure of acidity or alkalinity) of acid rain is 4 or less which means that it is highly acidic.

Therefore, the acid rain can damage crops, buildings and also endangers the aquatic life as the aquatic animals can die due to extremely acidic water.

How can we reduce air pollution?

Effective measures to prevent and discourage open fires

Use catalytic converters (to convert harmful pollutants into harmless) in the petrol-driven vehicles

Use electric cars (battery operated) to reduce gas emission

Use clean fuels to prevent the release of harmful gases and chemicals

Implement strict laws about the permissible level of sulfur

Remove sulfur from fossil fuels (desulfurization) before burning them (note that this is a very expensive approach).

The ozone layer:

The ozone layer plays a very important part in protecting the earth from the harmful radiations from the sun (ultraviolet radiations).

However, the chlorofluorocarbons (contain elements of carbon, chlorine and fluorine) are destroying the ozone layer rapidly. As a result, many countries have banned the use of chlorofluorocarbons.

The chapter atmosphere and environment require you to know that the carbon cycle is the process that maintains Carbon dioxide in the environment.

The processes that add Carbon dioxide to the environment are:

Respiration
Combustion of fuels
Decomposition

In respiration, glucose is converted into carbon dioxide, water and energy.

When fuels burn in oxygen, they produce carbon dioxide water vapours and heat energy.

Similarly, bacteria decompose the dead animals and plants and during this process, carbon dioxide is produced.

Apart, photosynthesis is one of the process that remove carbon dioxide from the atmosphere because green plants use carbon dioxide and water to produce glucose and oxygen.

The greenhouse effect:

Greenhouse gases (such as carbon dioxide methane) are the gases that trap radiation. In other words, they do not allow radiations to escape.

They play a very important role in maintaining the earth's temperature but global warming is increasing the average temperature of the earth.

The effects of global warming are:

The melting glaciers increase the ocean levels that can lead to floods

The rapid evaporation will cause less carbon dioxide to be absored by the water and as a result, carbon dioxide will be released in the atmosphere

The frequent spells of high temperature may lead to low crop yield and the areas might be converted into deserts.

Conclusion:

With this, our topic of the atmosphere and environment has come to an end. I hope that all your queries have been cleared through this article.

Thank You very much for reading and staying with me till the end. Practise plenty of past papers for this topic as it is a very important topic from examination point of view.

Mass, Weight and Density | GCE O Level Notes

2020-11-29T20:33:00.001+05:00

The topic of mass, weight and density is very important in GCE O Level physics because this topic contains some really useful concepts.

So, let's start (from the beginning) without further introductions and let me explain these terms, like "mass" and "weight" to you in detail.

Before understanding the concept of mass and weight, you have to remember that these two quantities, mass and weight, and not similar. How are they different? Let me tell you.

What is mass?

Mass refers to the amount of matter in a body. In other words, mass is the quantity of matter in a body. Since this quantity does not change with the location or shape, mass remains the same everywhere.

For example, your mass on the earth and mars will be the same because the location will not affect the "quantity of matter" of a body.

Mass is measured in various units but the SI (international system of units) is the kilogram (kg). However, other units such as gram (g) are also used to measure mass.

Note: Although mass is explained (and even determined sometimes) as the weight of an object, these two quantities are not the same. This is because weight is a force while mass is a property. We will take a look at weight later in this article.

Therefore, mass is a property which does not change with either shape or location.

What is "weight"?

In physics, the weight of an object is the gravitational force (gravity) acting on it. This gravitational pull to each and every object in the universe is exerted by the earth.

The SI unit of weight is Newton (N) because this quantity is a force and the direction of this force (vector quantity) is downwards.

The concept of weight developed with the development of Newton's laws of motion. Moreover, you should also remember that the weight increases with the gravitational force.

For example, your weight on earth will be higher than on mars because the gravitational force of the earth is stronger as compared to that of mars.

The weight of an object is dependent upon its mass because the greater the mass, the greater the weight (gravitation force acting on the object) of the object.

You should also be familiar with some formulas to understand the relationship between mass and weight.

Force (Weight) = (mass) x (acceleration)

Similarly, you should also know that:

Weight (W) = mass (m) x gravity (g)

Now, you should also know that how do we measure weight and mass?

We have machines like spring balance and electronic balance to give us the weight of an object but these devices are calibrated to give readings in kilograms (kg) or grams (g).

However, this does not mean that these machines give us the mass of the object because they are only calibrated to do so.

Similarly, we measure mass with machines such as the beam balance which compares the gravitational force acting on the object (recall that weight is the gravitational pull acting on an object).

These were some basic concepts about weight and mass and let us summarize these concepts with some key differences between mass and weight.

The difference between mass and weight:

Mass is the amount of matter in a body while weight is the gravitational force (pull) acting on the object.

The SI unit of weight is Newton (N) while the SI unit of mass is the kilogram (kg).

Weight is a vector quantity (has magnitude and direction) while mass is a scalar quantity (it only has a magnitude).

We can measure mass with a calibrated electronic balance or beam balance while weight can be measured with a spring balance.

Weight is dependent upon the location and shape while mass is independent of the location and gravitational field strength.

In this topic, you should also know that a gravitational field is a region where a mass has to experience gravitational attraction which comes as a force.

Inertia:

Mass is a measure of inertia and inertia is the reluctance of an object to change its position (during rest or motion) mainly because of its mass.

Let me make this simple for you. It is very difficult for an elephant to turn while moving because of its greater mass. However, a thin person can easily move and turn around because the mass is less.

You should also know that the greater the mass, the higher the inertia (reluctance or opposition). In simple words, inertia is the tendency to remain unchanged.

The concept of inertia is very important in physics mainly because this principle is used to elaborate on the motion of objects and how forces (acting on them) affect them.

Read:

Enzymes notes | GCE O level biology

O level physics Waves notes

These were some concepts which you should be familiar with and I have explained this term to you in detail so that you can easily manage questions related to this concept.

This takes us to another important topic in this chapter of mass, weight and density. So, let's dive into the topic.

Density:

When you divide the mass on an object by its volume, you get its density but this explanation is not enough to understand this topic.

In other words, density is mass per unit volume.

The SI unit of density is kilogram per cubic meter (kg/m³) and mathematically density is equal to the mass/volume.

It is to note that units such as gram per cubic centimetre can also be used to measure the density but these are not the SI unit of density.

To have a basic concept of density, keep in mind that the objects that float on the water have a lower density than water. Since the objects have a lower density than water, they float on water.

This was all about the topic regarding mass, weight and density but there are some practise questions for you to test your knowledge and prepare your exams.

Questions on mass, weight and density:

Question 1:

An object has a volume of 2280 cm³ and a mass of 570 g. Calculate the density of this object.

Solution: density = mass/volume

density = 570/2280 = 0.25 g/cm³

Question 2:

A bottle of cold drink has a mass of 0.5 kg and a density of 1000 kg/m³. Find the volume of the bottle, giving your answer in litres.

Solution: volume = 0.5/1000 = 0.0005 m³

To convert in litres, we multiply by 1000 and therefore, the answer will be 0.5 L (0.0005 x 1000).

Question 3:

Metal A has a density of 3.2 g/cm³ and metal B has a density of 5.5 g/cm³. The metal C is made by combining metal A and B in the ratio of 3:7 respectively. Metal C has a mass of 2500 g so, what is the density of metal C?

Solution:

First of all, we will calculate the mass of metal A.

mass of metal A = (3/10) x 2500 = 750 g (because the mass of metal A is 3:10 to the mass of metal C).

Similarly, the mass of metal B will be = (7/10) x 2500 = 1750 g (because the mass of metal B is 7:10 to the mass of metal C as metal C is the combination of metal A and metal B).

Now, we have to calculate the volume of metal A and B.

The volume of metal A = mass/density = 750/3.2 = 234.38 g/cm³

The volume of metal B = mass/density = 1750/5.5 = 318.18 g/cm³

The volume of metal C = volume of metal A + volume of metal B = 234.38 + 318.18 = 552.56 cm³

Density of metal C = mass/volume = 2500/552.56 = 4.5 g/cm3

Question 4:

On the moon, a book has a mass of 0.5 kg. This book is brought to the earth (the gravitational field on earth is stronger). On the earth, the book will have:

A. The same mass and more weight

B. The same mass and weight

C. The same weight and less mass

D. The same weight and more mass

Solution: Answer A (because since the gravitational field is stronger, the book will have more weight but the mass is not affected by the location).

Question 5:

If the density of water is 1000 kg/m3, what is the mass of 1 cm3 of water in grams?

Solution: mass = density x volume

mass = 1 x 1 = 1 g (because 1000 kg/m3 is equal to 1 g/cm3 after conversion).

Conclusion:

With this, our topic about mass, weight and density has come to an end. I hope that all your questions are answered through this article.

Make sure to solve the practice questions given above and solve plenty of past paper questions to ace your examination. I hope that these notes were helpful for you and thank you very much for reading.

Enzymes Notes | GCE O Level And IGCSE Biology

2020-11-09T18:21:00.004+05:00

Enzymes are those chemical (biological) catalysts that speed up a chemical reaction and they remain unchanged at the end of a reaction.

However, this definition is not enough to meet the requirements of your syllabus about enzymes notes. So, let's start from the very beginning without further introductions.

What are Enzymes?

There are several reactions that require very strong heat to undergo completion. It is not feasible (commercially) to meet all conditions for some reactions.

As a result, catalysts are used to speed up (or alter) these reactions. It is to note that enzymes are organic catalysts usually made up of proteins and their primary function is to speed up slow reactions.

There are several reactions in our everyday life in which enzymes play a very vital role. Let's take a look at some examples to understand the use of enzymes.

The Application of Enzymes:

In our body, many complex substances are broken down into simpler ones.

For example, glucose is oxidised in a human body to release energy while water and Carbon Dioxide are liberated. This is a very slow reaction but with the help of enzymes, the oxidation of glucose becomes a speedy process.

Digestion is also a process that involves enzymes.

The food that animals consume consist of large molecules that are either insoluble in water or non-diffusable. These molecules may comprise of carbohydrates, fats and proteins.

With the help of enzymes, these large molecules are converted into smaller and simpler substances which allow them to diffuse across the cell membrane.

For instance, enzymes such as Carbohydrases and Amylase breakdown starch into sugar while lipids breakdown fats into glycerol and fatty acids.

The synthesis of complex substances from smaller ones also involves enzymes.

For example, protein formation may take place when multiple amino acids are used by the cells. Apart, the enzymes may also be involved in the breakdown of poisonous gases.

These are some examples to show how enzymes are involved in the life of organisms but you should know that specific enzymes only perform specific functions.

For example, protease (enzyme) can also breakdown proteins into amino acids but it cannot breakdown starch or fats. Moreover, enzymes are only produced when they are needed.

Why are Enzymes required in small amounts?

As discussed earlier, enzymes remain unchanged at the end of a reaction. In other words, enzymes are not altered during a chemical reaction.

As a result, the production of enzymes is less because they can catalyse a large number of chemical reactions.

The same enzymes molecule can be utilised for different reactions because it can be used over and over again. This explains why enzymes are required in a minimal amount.

This takes us to another key concept in enzymes notes which is about the "lock and key hypothesis".

The "Lock And Key Hypothesis":

To understand this concept, you should revise the fact that specific enzymes can only catalyse specific chemical reactions which have been discussed with examples above.

Every enzyme has an "active site" on which the substrate fits and get catalysed. What is an active site? Let me explain you.

These are the depressions on enzyme molecules where the substrate (any substance in which an enzyme acts such as fats, proteins and starch) attaches with the enzyme molecule.

When the enzyme and substrate bind together, the reaction takes place and a product is formed. This process is also referred to as the enzyme-substrate complex.

You should also be familiar with the effect of temperature and pH on the enzyme activity. So, it is time to cover this topic as well.

The effect of temperature on enzyme reaction:

Temperature plays a very important role in the activity of an enzyme because enzymes have an optimum (suitable) working temperature.

If the temperature is very low, the enzymes will not display their function properly because, at low temperatures, they are usually inactive.

As a result, less activity is performed.

The increase in temperature will also increase the activity of an enzyme until it reaches its optimum temperature (at which the enzyme activity is the highest).

If the temperature is further increased, it can denature the enzyme. Well, what does this mean? Let me explain this to you!

Since enzymes are usually made up of proteins, high temperature can cause a change in their shape as the three-dimension structure is disturbed.

Read:

GCE O Level Biology Drugs Notes

Speech Writing Sample and Format

Now, let me tell you the effect of pH on the enzyme activity.

Effect of pH on enzyme activity:

The pH refers to the acidity and alkalinity.

Some enzymes show the most activity in slightly acidic conditions while some show their activity in alkaline conditions. Therefore, the enzyme activity is dependent upon pH as well.

However, a massive increase in the pH (either acidity or alkalinity) can completely denature an enzyme.

This ends up our topic about enzymes notes and the important concepts in this topic about enzymes.

Conclusion:

Thank You very much for reading and staying with me till the end. I hope that all your questions about enzymes notes have been answered.

Stay tuned for more useful resources and some of the key points covered in this article are listed below:

What are enzymes?
What is the lock and key hypothesis?
The effect of temperature on enzyme activity
The effect of pH on enzyme activity

Drugs Notes pdf | GCE O Level and IGCSE

2020-10-11T21:01:00.001+05:00

Drugs is a very important topic when it comes to your exam preparation for Biology and this article will provide you with some useful and relevant information regarding drugs notes for GCE O level and IGCSE.

What is a Drug?

According to your syllabus, a drug is a substance (chemical) which is responsible for either modifying or affecting the chemical reactions in a body.

You should remember that the topic which you are studying is the "use and abuse of drugs". This is important because there are several uses of drugs as well and we will also take a look at them. You can categorise drugs as:

Medicinal drugs
Socially accepted drugs
Drugs of abuse

Let's take a look at all these categories in detail now.

Medicinal drugs

These drugs are responsible for treating multiple diseases and there are various drugs that are used to alleviate (reduce) pain and even in different surgeries.

The best example of medicinal drugs are antibiotics that are used to treat the ailments that are caused by microorganisms. It is to note that the antibiotics can also be "man-made".

Tetracyclines, Penicillins, Cephalosporins and Erythromycin are some types of antibiotics. The way these antibiotics work is different because they are used to treat different diseases and therefore the outcome is also dissimilar.

Anaesthetics are those drugs that relieve pain from a body and Cocaine and Novocain are among the examples for "anaesthetics". Analgesics (such as aspirin) reduce pain and fever but they do not affect one's consciousness. It is to note that a large dose can harm someone due to its side effects.

Related: O Level Physics Wave Notes

There are some drugs which you should know about in detail because of your GCE O level and IGCSE syllabus requirements. So, let's discuss those topics now.

Alcohol

This drug is widely used in beverages and it is broken down in the liver of a body. When alcohol is consumed in a large amount, it has drastic effects on a body and especially on the nervous system.

Some of them are:

The brain functions slow down.
Some people feel extra anxiety and for some people nervous tension is relieved.
One's self-control is reduced.
Muscular coordination is also affected.
Blurred vision and slurred speech.
It is an addiction that increases with every consumption.
Humans digestive system is affected by the risk of gastric ulcers.

Heroin:

This is one of the drugs that are most widely abused and the addiction of this drug is extremely serious. This drug reduces hunger and makes its consumers sleepy and weak as one become dependent upon the drug.

Other negative effects are:

Upset stomach
Anxiety
Watering of eyes
In severe cases, death

Therefore, this drug is becoming a problem which is progressing extremely fast and it is mandatory to acquire knowledge about it to refrain from its abuse.

Smoking:

You should also have some knowledge regarding this topic because it is extremely important from your examination point of view. There are multiple reasons why people smoke.

The younger ones consider it a symbol of adulthood while some people smoke to indicate that they are no longer dependent upon others. Some other reasons are listed below which you can also consider:

Symbol of maturity, happiness and success
To hide one's weaknesses and shortcomings
Curiosity
Peer pressure
Smoking is an addiction because the cigarette is a drug
For some people, it is a source to relieve tension

Nicotine is the addictive substance in a cigarette which allows the blood to clot easily. This substance is what makes a smoker dependent upon smoking.

See: O Level Speech Writing Sample

Carbon Monoxide damages the lining of blood vessels and it disturbs the functions of a body because it replaces oxygen which can prove to be dangerous. It is also submitted on the inner lining of your arteries which make smoking dangerous.

Tar is a blackish-brown substance that gets deposited on the lungs and it contains many cancer-causing chemicals. Moreover, this substance can cause breathing problems because air passages can be blocked and trachea can also be affected.

Conclusion:

The drugs notes have been provided to you and I hope that all your queries have been answered as well. Thank You very much for reading and staying with me till the end. This topic is important from paper 2 perspective but multiple questions in paper 1 can also appear.

According to me, a general reading for this topic is more than enough and if you know some effects of drugs such as alcohol and heroin, you are good to go.

Make sure to have a brief knowledge about smoking and substance such as Tar and Nicotine because it is also required by your syllabus.

Khilafat Movement O Level Pakistan Studies (2059) Notes

2020-08-04T20:42:00.005+05:00

Khilafat Movement? If it is what made you come here, then be confident that you are at the right place.

This movement was not started immediately. It has a background which is necessary to understand the movement. So let’s start from the very beginning.

What was the khilafat movement?

It was the movement started by the people of the subcontinent to protect Turkey and the head of the Islamic state, the Khalifa as he was of immense importance to the Muslim world.

Turkey had supported Germany and Austria in the first world war against Britain and thus after the decisive victory of Britain, Prime Minister Llyod George was ready to punish Turkey and Khalifa.

Muslims who had been promised a good fate of Turkey before the war were not happy by this decision and thus came up with the Khilafat Movement to achieve their goals, to protect Turkey.

Who was the Khalifa at the time of the Khilafat Movement?

It was Muhammad V| also known as Mehmet V|, Mehmed Vahdattin and Mehmed Vahideddin. He came to the throne of 4 July 1918 (just a few days before the end of WW|). He succeeded Muhammad V and thus was the last Sultan of the Ottoman empire.

He was very unpopular among the Turkish people because, after World War |, his representatives accepted the Treaty of Sevres which aimed at dismantling the Turkish empire.

The conditions at the end of 1922 became worse such that the Khalifa wrote to the British to provide him shelter in Britain. Though he was unable to attain this he went into exile in Turkey.

Why did the Khilafat Movement Started (Reasons for the beginning of the Khilafat Movement):

Firstly, there were some so-called ‘deep-seated Muslim fears’. To elaborate, it should be known that at that time there were negotiations going on between Russia and Britain on how to govern Persia and Afghanistan (both Muslims states).

However, the views of the local people were not given any sort of effect and thus their views were undermined. Therefore, the Khilafat movement aimed to crush these fears as-well by taking a firm stance on these issues.

Similarly, the prominent Muslim leaders of that time such as Maulana Abdul Kalam Azad were to the point that the British were trying to instil a fear of Hindus among Muslims so that they come closer to British and were forced to work with them.

Therefore, these Muslim leaders considered cooperation with the British as a Satanic act and thus declared the slogan of Khilafat to achieve their own aims!

Moreover, the Indian Muslims were reluctant to fight against their fellow Muslim brothers of Turkey in World War |. However, the British needed the support of Muslims to win the war and thus could not fortify all their Muslims troops that formed a majority of the British army.

Therefore, the British promised the Indian Muslims that the Turkish empire would not be harshly treated and Muslim association with Turkey would be kept in mind before further actions against Turkey.

However, when the British won the war, they were to the point that Turkey should also be punished as Germany and Austria were.

This viewpoint was against the promise of British made with Muslims and thus the movement was started to prevent the ideas of the British from coming into action.

Lastly, the Caliph was of immense respect for Muslims throughout the world. He was the leader of Makkah, Madinah and Jerusalem that were some of the most important sites for Muslims.

That is why the Muslims were not ready to see the Caliph being deprived of power. In the same way, the Muslims were strongly resented to the massive imprisonment of Muslims during the 1920’s.

Now, it is to note that despite all the efforts, the Khilafat movement failed. But why?

Reasons for the Failure of the Khilafat Movement?

The Hijrat movement was one of the reasons which morally disillusioned the Muslims. During the 1920’s, Muslim leaders such as Maulana Abdul Kalam Azad and Maulana Abdul Bari declared India as Darul-Harb (land under non-Muslim war, likely to lead to future war).

Therefore on the command, 18,000 Muslims from all over India migrated to Afghanistan as a comfortable lifestyle was promised.

Initially, the number was welcomed by the Afghan government but the surging number was asked by the Afghan government to return back.

When the Muslims returned, they found their lands equipped and jobs lost. This made Muslims lose heart who was not willing to support the movement anymore.

Another reason for the failure of the khilafat movement was the leadership vacuum. Well, what does this mean?

This means that at the time of khilafat movement, certain prominent figures that supported the movement were jailed. Due to this, there was no one to lead the Muslims at this crucial stage.

This created disunity among the Muslims which was fully exploited by the British.

Mustafa Kemal Ataturk abolished the khilafat in Turkey. When there was no khilafat, there was no reason to continue the khilafat movement. Therefore, the khilafat movement came to an end.

Apart, the Muslim league and congress supported each other for their own advantage. When the congress saw that their support to khilafat movement was no longer useful for them, Gandhi simply decided to withdraw his support from the movement.

Similarly, the violence (such as chauri chaura incident) also forced Gandhi to withdraw his support form the movement.

The Mophlas were those Muslims that were present in the Northern India. They managed to kill a number of British and the Hindus.

This attitude of the Mophlas disturbed British and the Hindus therefore, the British punished them brutally. The Hindus also withdrew their support for the khilafat movement due to this.

Conclusion:

With this, Khilafat Movement Pakistan Studies (2059) Notes have come to an end.

Thank You very much for reading.

O Level Physics Waves Notes PDF - The Root Bridge

2019-11-04T23:41:00.005+05:00

The CAIE Syllabus for Transverse Waves and Longitudinal Waves (sound) is as follows :

General Wave Properties/Transverse Waves:

Content

13.1 Describing wave motion 13.2 Wave terms
13.3 Wave behaviour

Learning outcomes

Candidates should be able to:

(a) describe what is meant by wave motion as illustrated by vibrations in ropes and springs and by
experiments using a ripple tank.
(b) state what is meant by the term wavefront.
(c) define the terms speed, frequency, wavelength and amplitude and recall and use the formula velocity = frequency × wavelength.
(d) describe transverse and longitudinal waves in such a way as to illustrate the differences between them.
(e) describe the use of a ripple tank to show

(1) reflection at a plane surface,

(2) refraction due to a change of speed at a constant frequency.

(f) describe simple experiments to show the reflection of sound waves.

Sound (Longitudinal Waves):

Content

Learning outcomes

Candidates should be able to:

(a) describe the production of sound by vibrating sources.
(b) describe the longitudinal nature of sound waves and describe compression and rarefaction.
(c) state the approximate range of audible frequencies for the healthy human ear as 20Hz to 20000Hz.
(d) explain why a medium is required in order to transmit sound waves and describe an experiment to demonstrate this.
(e) describe a direct method for the determination of the speed of sound in air and make the necessary calculation.
(f) state the order of magnitude of the speeds of sound in air, liquids and solids.
(g) explain how the loudness and pitch of sound waves relate to amplitude and frequency.
(h) describe how the reflection of sound may produce an echo.
(i) describe how the shape of a sound wave as demonstrated by an oscilloscope is affected by the quality (timbre) of the sound wave.
(j) define ultrasound.

(k) describe the uses of ultrasound in cleaning, quality control and pre-natal scanning.

Syllabus Source :

Notes For Transverse Waves :

What Is Meant By Wave Motion :

Wave motion is the movement and progress of Waves which is the change in state from rest to equilibrium. It can also be defined as the propagation of a wave. Therefore a wave is a disturbance that transfers energy from one point to another which is formed by energy transfer.

Illustrating Wave Motion Through ropes:

From the above picture, where the rope is joined at the one end from the tree and is disturbed on the other end by a person, disturbance in the medium is created and a wave is formed.

The Kinetic Energy from the moving hand is transferred to rope particles which move up and down. In this wave progresses until it reaches the tree. It is to note that the wave direction is perpendicular to the particle vibration direction which is a major property of transverse waves.

Illustrating Wave Motion Through Ripple Tank :

With the help of oscillating paddle, disturbances are created in tank, hence wave is produced. When the wave progresses along with the ripple tank, the water particles move up and down (showing transverse wave).

It is to note that the waves which are produced are only in a circular motion but still are perpendicular to the up and down moving water particles. The table shows the moving waves (shadow).

Illustrating Waves with Slinky Spring :

The wave demonstration is spring is very similar to that of rope. It is to note that springs can produce both transverse and longitudinal waves, but here we are only viewing transverse case. When spring is moved from left to right or vice versa, the transverse waves progress through the spring which can be proved as the waves form a 90-degree angle with particles.

What is a WaveFront :

A wavefront is an imaginary line on a wave that connects all adjacent points in phase. It can be drawn by joining all adjacent waves crests in the phase of different waves. The wavefronts can be straight lines, concentric centres and other shapes.

The surface can also be said to be the locus of points that have the same phase. The wavefront is perpendicular to the ray that represents an electromagnetic wave (EM). The plane in which the electric and magnetic field vectors lie is tangential to the wavefront at each and every point.

Important Terms:

Speed:

The wave speed is the distance travelled by the wave per second, it is derived from the formula, Speed = Distance / Time.

Frequency:

The frequency of a wave is the number of complete waves produced in one second. The SI units of frequency are Hertz. It can also be described as a number of crests or trough that go through a point per second. Frequency and time period are inversely proportional (when one increases other decreases) and the higher the frequency, the greater the waves.

Wavelength:

Wavelength is the distance between identical points in the adjacent cycles of a wave produced. The identical points maybe two consecutive crests or troughs.

Amplitude:

The maximum vertical displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position.

Cambridge students should also know :

Wave Speed = Frequency * Wavelength

(v = f*w) where f = frequency and w = wavelength

Differences between transverse and longitudinal waves:

A longitudinal wave is a wave where the movement of the medium is in the exact direction as the wave. On the other hand, a transverse wave is a wave where the movement of the medium is at a perpendicular to the wave direction.

Examples of longitudinal waves include Sound waves in air, waves formed along with a compressed spring and seismic waves whereas an example of transverse waves includes water waves.

Longitudinal waves cause changes in the pressure of the different parts of the medium through which they go through. On the other hand, the transverse wave does not cause pressure changes in the medium through which they move.

Longitudinal waves can be transmitted through all the three types of media, that are solids, liquids and gases. Apart from transverse waves can only be transmitted through solids or over liquid surfaces.

Longitudinal waves travel in the form of alternate compressions and rarefactions whereas transverse waves can be transmitted in the form of crest and toughs.

Speed of longitudinal waves is comparatively less than that of transversely moving waves.

Cambridge also requires its candidates to illustrate reflection and refraction of sound :

By placing a metal bar in the tank and tapping/clicking the wooden bar a pulse of three of four ripples can be forwarded towards the metal bar. The ripples reflect through the bar. If the bar is placed at an angle to the wavefront the reflected waves can be observed to obey the law of reflection. The angle of incidence and angle of reflection will be equal.

If a sheet of glass is placed in the tank, the depth of water in the tank will be shallower over the glass and another deep region would form. The speed of a wave in water depends on the depth, so the ripples slow down as they pass over the glass, means they move from deep to shallow. This causes the wavelength to decrease as well.

Sound:

How Sound Is Produced:

Sound is formed due to disturbance in a medium, like the transverse waves. However, the disturbance is caused by vibrations in either solid, liquid or gas. The vibration causes waves to form which are longitudinal waves as the medium around vibrations itself vibrate. The wave direction during this case is parallel to particle vibration direction, such as in a guitar or tuning fork.

Sound Waves are longitudinal in nature primarily due to their parallel particle vibration to wave direction and a series of compression and rarefaction;

Compression And Rarefaction For Sound:

Sound waves progress and are produced due to a series of compression and rarefactions. During the compression, the pressure increases due to closely packed particles and during rarefaction, the pressure decreases as particles are spaced away as compared to those of compression. The diagram below explains the scenario :

AND:

Now when you know about the basics that a sound is a form of a longitudinal wave, you should know that the audible human frequency is between 20 Hertz to 20,000 Hertz. Any sound above or below this range cannot be heard by humans. With growing age, this limit even narrows.

Why Sound needs a medium and cannot propagate through a vacuum?

Sound needs a medium for their propagation like solid, liquid or gas to travel because the molecules of solid, liquid and gases carry sound waves from one place to another. Sound cannot progress through the vacuum because the vacuum has no molecules thus sound cannot progress. It is to note that sound travels fastest in solids followed by liquid and then gas.

Experiment to show that sound needs a medium to travel:

In the above case pump the air out of a jar, then allow the sticker to strike the bell. After striking, the bell could be viewed moving but one cannot hear the sound. However if the air is pumped back and the experiment is repeated, then one hears sound as well.

See: O Level Chemistry Periodic Table Notes

Experiment to show the speed of sound:

Place two people exactly 1000 meters apart with one man a gun and other with the stopwatch. When the man shoots with the gun and other person watches the gun powder, let him start the stopwatch and stop when he hears the sound. Repeat the experiment to reduce human error. Then divide 1000 (distance) with the time on the stopwatch to get speed as
Speed = Distance/time

Relating loudness and pitch with amplitude and frequency:

The loudness is directly related to the amplitude. The higher the amplitude, the higher the loudness of sound.
Likewise, the pitch is a property of sound, that is related to the frequency. These both are also directly related as when higher the frequency of the sound, the higher the pitch. For example, the pitch of the sound of 200Hz is lower than that of 400Hz.

It is also really important to know the pitch production with the length of the tuning fork. You should always remember that that the tuning fork with long prongs produce a sound with a lower frequency than the tuning fork with shorter prongs. This is because tuning fork with longer prongs produces sound with long-wavelength, hence with low frequency, therefore low pitch and vice versus with that of shorter prongs.

All You Should Know About Echo For your CIE:

Echo is the repetition of sound due to the reflection/bouncing back of sound due to contact with a surface. An echo is formed when a sound hits a surface and reflects back at the same angle which is produced when it strikes the surface or in easy words its angle with the normal
The angle of Incidence = Angle Of Reflection (only for reflection of sound/echo in this case)

Lastly, you should only that the echo is used for echolocation and for measuring large distances.

A timbre is the quality of a sound and is affected through various factors. It is affected by factors such as wavelength m speed and frequency. A CRO (cathode ray oscilloscope) displays the sound waves in the form of waves which is like

Finally, you should also have knowledge about ultrasound and its uses. Ultrasound is sound waves with frequency higher than 20,000Hz that is the upper limit of audible human hearing range!

USES:

Ultrasonic cleaning uses cavitation bubbles induced by high-frequency pressure (sound) waves to agitate a liquid.

It is also used for ensuring food quality by penetrating the rays into food substances.

Lastly, it is also used for the prenatal scan as its rays are not at all harmful to the women.

O level Speech Writing Sample - The Root Bridge

2019-11-01T21:45:00.006+05:00

In the following article, there is a speech question that appeared in the Cambridge examination. The Root Bridge has provided you with a sample of answers to discuss the positive and negative points which students commit during speech writing.

Before getting into it, it is essential to know the features of Speech Writing.

Features Of Speech In CIE:

Welcome the audience
Introduce yourself
Tone a language depends on the context (audience)
Use the 'you tone' to involve the audience
Use humour
Include pauses gestures and fillers (Umm.. etc) but sparingly
Refer to facts and statistics
Use a variety of sentence structures
Include famous quotes
Express Strong opinions expressed with logical reasoning
Use figurative language such as facts, metaphors etc ...
Ask Rhetorical Questions (usually at the beginning at the end, can be included in between as well)
Use proper Nouns
Use emotive language such as 'I feel delighted to' etc
Vivid language
Thank audience at the end

Speech Writing O Level:

Question:

Your best friend is a popular person at school and is very successful both inside and outside the classroom. Your friend is leaving school to move overseas. Your teacher, Mr Johnson, asks you to make a speech to your classmates on the last day of term wishing your friend goodbye and good luck.

Write your speech. You must include the following:

• the name of your friend and where your friend is going
• why your friend is moving
• what you and your classmates will miss about your friend.
Cover all three points above in detail. You should make sure your speech is both polite and friendly.

Start your speech, ‘Mr Johnson and friends...’

Answer:

Mr Johnson and friends, let me begin my speech with my sincere gratitude to all of you for your presence. However, I feel really unhappy to tell you that a very well known figure from our school is leaving us this Friday.

Adam, do you know him? Well, who does not? Mr Johnson and all my respected fellows, Adam is amidst these last days which he is spending with us. He will be leaving us this Friday for Manchester, England. Anyways I know none of us should actually be sad for Adam moving overseas. It will be just a physical day to day connection that would be missing, but we all will be virtually connected way too strong. Adam would be living in a strong long-distance friendship.

As you all know, we only have three months left before we pass out from School. Adam is indeed a very intelligent student. He had planned to join his father in Manchester and continue his further studies. I believe all of you would be praying for the best of Adam's future so do all of us.

Whether it is Adam's academic efficiency that we would miss but his excellence in co-curricular activities is also leaving us with much to debate.

I thank you all and especially Adam to give me your precious time and listen to me attentively. Umm well, that's what I have to say. Thank you all once again and I would conclude my words by saying:
"Great friends are hard to find, difficult to leave, impossible to forget."

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Comments On Sample:

Overall the speech written by the candidate is satisfactory. It has properly fulfilled the format of directed writing by included five required paragraphs: Introduction, Content point 1, Content point 2, Content point 3 and Conclusion. The sample included has also beginner the report by welcoming the audience.

The tone is fine and the audience is engaged by 'you tone'.Sparingly fillers are used which is good.

Similarly, the sample includes a famous saying at the end and emotive language is also used. In addition, the audience is thanked at the end to conclude the speech.

However, the writer has not introduced himself/herself. Facts and statistics are not present.

There are simple and compound sentences but complex and compound-complex are very rarely found. Figurate language is also lacking.

20 + Interesting Facts About Stars - The Root Bridge

2019-10-31T15:33:00.027+05:00

Photo by Jeremy Thomas on Unsplash

Stars? Who hasn't heard about them? But are you completely aware of Stars?

Let's make it simple. Lets even arouse your interest in Stars by providing you factual interesting information about stars.

Before getting into the articles, just enjoy an inspirational saying an of Sir Stephen Hawkins on Stars:

“Remember to look up at the stars and now down at your feet. Try to make sense of what you see and wonder about what makes the universe exist.

Be curious. And however difficult life may seem, there is always something you can do and succeed at. It matters that you don’t just give up.”

What are Stars?

Star is something that refers to the astronomical object, consisting of a luminous spheroid of plasma enacted by gravity. The nearest star to Earth is the Sun.

Many other stars are visible to the humans from Earth directly during the night. However, these are tremendously far apart from the Earth.

These are not that small that they appear to the naked eye but due to their immense distance, they appear like that. Astronomers have categorised star catalogues that identify the known stars and provide standardised details.

The universe observed contain an estimated 1×10²⁴ stars but most are invisible to the naked eye from Earth, including all stars outside our galaxy.

Have You ever wondered why do we call stars as stars?

The name ‘Star’ is derived from the ancient Greek word 'aster' which means 'a star''

However, for some people, the word star is from the Middle English word sterre, from the Old English word steorra, which is from the Proto-Germanic word sterron.

Shortly the word star as a result of a series of transformations from an earlier designated word for those twinkling objects in the sky.

Quite obviously the name of stars varies with different languages, so why do we call stars as stars? Because it was named it!

Photo by NASA on Unsplash

Facts About Stars are as follows:

Twinkling is not a property of the stars:

Twinkling is not a property of the stars, but of the planet Earth’s turbulent atmosphere/surrounding. As the light from a star passes through the atmosphere, especially when the star appears near the horizon, it must cross through certain layers of often rapidly differing density.

This has the effect of deflecting the light slightly as these were similar to a ball in a pinball machine.

When the light ultimately gets to the eyes, but every deflection causes it to change slightly in colour and intensity. The result is “twinkling.”

Above the Earth’s atmosphere, however, stars do not twinkle. So now you better mind saying:

Twinkle Twinkle Little Star.

The stars absorb all radiations that fall on it:

The stars absorb all radiations that fall on it, but it also radiates/reflects back into space much more than it absorbs(taking in). Thus a star is a black body that glows with magnificent brilliance.

A star dying:

When a star is about to dye it turns into a “white dwarf", when the star completely uses up all of the chemicals required for its nuclear fusion (joining of daughter atoms) reaction, it will fuse a large clump, which will release high radiation white light until it finally darkens for good.

The coolest star:

The coolest stars in-universe are red and these are around 3500 kelvin.

There are estimated to be up to 400 billion stars in the galaxy:

There are estimated to be up to 400 billion stars in the galaxy, and over 500 million galaxies in the Universe.The estimate that's out there is 200,000,000,000,000,000,000,000 stars.

That’s a septillion – and even astronomers are just guessing. There could be more.

The colour of a star:

The Star sun actually is white in colour if views from space.

10 to 20 million old stars:

The five stars of the Southern Cross are believed to be between 10 and 20 million years old.

The brightest star:

Sirius is the brightest star which is 20 times brighter than the sun , great to know that, isn't it?

Shootings stars are not really stars. These are the rock or dust that when it hits the Earth’s atmosphere, moving at such a fast rate, it heats up and glows as it travels through the atmosphere.

According to astronomers, these are meteors.

There are officially 88 different constellations of stars in our hemispheres.

Shooting Stars are really fast, reaching up to a speed of 120,000 miles per hour!

The colours of a shooting star may sometime also direct towards the minerals that make up the space rock.

Different elements emit different-coloured light when they burn. Iron, one of the most common elements found in meteors.

The Sun is over 4 billion years old!

Some stars are known as binary stars as they have a twin star nearby that looks similar to them.

The universe has over 200 billion stars.

If you moved the big star to our solar system, it would stretch beyond Earth’s orbit.

Less massive stars are expected to live much longer than bigger stars. The completely opposite can be said for small red dwarfs, who are burning their hydrogen in an extremely slow rate.

The core of a star reaches 16 million degrees Celsius.

Neutron stars can spin/rotate at 600 rotations per second.

Mind Blown with these, right? So now let's have some looks on quotes regarding Stars to make these articles even informative and interesting:

Moonlight drowns out all but the brightest stars (J.R.R Tolkien).

He cosmos is within us. We are made of star-stuff. We are a way for the universe to know itself. (Carl Sagan)

All we ever see of stars are their old photographs. (Alan Moore).

I love the stars.
Because they can't say anything.
I love the stars.
Because they do not judge anyone. (Natsuki Takaya).

When he shall die,
Take him and cut him out in little stars,
And he will make the face of heaven so fine
That all the world will be in love with night
And pay no worship to the garish sun. (William Shakespeare).

FAQ on Stars:

Q: Do all Stars have a name?

ANS: Around 250 0f the bright stars do only.

Q: How can the distances to the near stars measure?

ANS: The distances to the nearer stars are measured mathematically, by the use of trigonometric parallax. "Parallax" is a word of Greek origin meaning the difference in the apparent positions of an object.

Q: How many stars can we see on a clear night?

ANS: A man can see between 3,500 and 4,000 stars.

Q: What is meant by a giant star?

ANS: It is a star whose diameter is between 10 times the diameter of the Sun and 100 times its diameter.

Q: What are the sizes of the supergiant stars?

ANS: The largest stars are about 3,000 times the diameter of Sun. In kilometres, this is from about 5 thousand million kilometres in diameter to about 160 million kilometres.

Conclusion / My Final Thoughts:

Surely it is a great experience to go through stars. The following article does not only provides facts about stars but also arouses readers interests by interesting quotes and sayings. To conclude, the study and knowledge of Stars is a very very vast topic. Any article cannot be capable of providing sufficient details of the topic but we hope that your question is answered. The Root Bridge thanks you for reading!