Category: Science

Introduction

Astrophysics deals with the knowledge of the universe beyond this Earth. It explores the processes that occur in the depths of space and astrophysicists also study the physics of the various planets and stars in and beyond and the solar system.

Closer to home, we have a field of science known as geology, which is the study of the Earth’s physical structure and substance. Our knowledge of what lies inside the Earth as well as various phenomena that occur due to changes within this composition is all classified under geology. In this article, we are going to explore what the Earth is made out of and how its composition is classified.

What is Earth?

Earth is the third planet in our solar system and the fifth largest by size. It is a terrestrial planet, meaning that it is mostly made up of solid, rocky materials. The surface of Earth isn’t smooth. Rather, it is covered in mountains and valleys in some portions while water covers the remaining 70 percent of its surface, earning it the nickname “ocean planet” and giving it the ability to support life. Its atmosphere is mostly composed of nitrogen and oxygen and a strong magnetic field around the planet prevents it from the effects of solar radiation. Each day on Earth lasts 24 hours and each year comprises 365.25 days. Interestingly, Earth is the only planet in the solar system that has exactly one natural satellite: the moon.

Earth’s Magnetic Field

The intrinsic, natural magnetic field of the Earth arises due to the convection currents developed inside the core of the Earth and extends all the way into space. It gives rise to a layer of the atmosphere known as magnetosphere and is also known as geomagnetic field.

Earth’s magnetic field.

Convection currents in the core develop due to the flow of molten materials like iron inside the core of the Earth. Since these materials contain charged particles, their motion gives rise to a current which creates the magnetic field of the Earth. Due to this field, the Earth can also be thought of as a bar magnet, though its poles do not coincide with the geographical poles.

Layers of Earth

The physical composition of Earth is classified into the crust, the mantle, the outer core, and the inner core. The following figure depicts this classification and we will discuss each layer in detail.

Layers of the Earth

Inner core

• The core is the deepest and hottest layer of the Earth and it lies at the very center.
• It is composed of solid metals like iron, nickel and trace amounts of gold, cobalt, and platinum.
• The inner core has a temperature of around 5,200 ℃.
• Due to the enormous pressure, the core remains solid despite the temperature far exceeding its contents’ melting points.
• The inner core is approximately 1220 km in radius.
• The lighter elements are present near the top of the core while the heavier elements tend to shift downwards. This process is an exothermic one and it heats up the planet.

Outer core

• The outer core lies above the inner core and is the only layer containing iron, nickel, and other substances in a liquid state.
• Its temperature is around 4000-9000 ℉. 
• The rotation of the Earth creates a convection current in this layer, forming a magnetic field.
• The outer core is about 2200 km thick and carries 15% of the Earth’s volume.
• Its density is approximately 9.5 to 14.5 g/cc.
• The point of discontinuity between the core and mantle is known as Guttenberg’s discontinuity while the inner and outer cores are separated by Lehmann discontinuity.

Mantle

• The mantle is the solid layer beyond the core and is about 2900 km thick.
• It occupies 84% of the Earth’s volume and is made of elements like silicon and magnesium.
• Its density is in the 3 to 5 g/cc range. The mantle is in a solid state.
• Its upper and lower portions are separated by the Repitti discontinuity. 

Crust

• The crust is the outermost, solid layer of the Earth upon which we live. Its thickness varies greatly from 5 to 40 km.
• Most of the crust is covered in water and in oceanic regions, the crust is only 5-10 km thick.
• The crust occupies a meager 1% of Earth’s total volume and it forms the lithosphere of the Earth.
• The outer crust contains sedimentary rocks made up of silicon and aluminum and has a density of around 3 g/cc.

Summary

So far, Earth is the only known planet that supports life. It lies third in our solar system and carries its own magnetic field to prevent it from solar winds. The study of the physical structure and substance of Earth is known as geology and in this article, we explored the various layers that make up this planet. These included the crust, the mantle, and the core.

Frequently asked questions

1. What is hydrostatic equilibrium?

Hydrostatic equilibrium refers to the balance between the gravitational force and the pressure of a gas or liquid. It is a self-regulating force. 

2. What is the percentage of fresh water on the Earth? 

While about 70% of the Earth’s surface is covered in water, only a small 3% of it is fresh and out of this 3%, 1% is in the form of icecaps and glaciers. The remaining 2% is what we use for our daily activities. 

3. What are the conditions necessary for the geodynamo process?

The Earth can create its own magnetic field given that:

1. It is rotating at a sufficient velocity.
2. Its core contains conductors in a liquid state.
3. There is enough internal energy to create the convection current.

4. What elements are present in the inner core?

The inner core is mainly made up of iron (around 80%). About 5 to 15% of it is nickel, 2 to 3% is siderophiles, and the remaining 5 to 10% is sulfur and oxygen. 

5. Why is the core so incredibly hot?

The heat provided during the formation of the Earth, along with the heat generated due to friction and radioactive decay of elements makes the Earth’s core immensely hot.

Introduction

Electronics is a branch of physics that focuses on the behavior of electrons in electronic circuits. Unlike classical electrical engineering, electronics employ active devices as components. Note that active devices are devices that can control the flow of electricity in a circuit. On the other hand, passive components only consume electricity but cannot regulate it. Vacuum tubes which have the ability to control the flow of electrons, were initially fundamental to electronics but that technology is now obsolete. Today, you can create much more intricate circuits in much smaller form factors using transistors. 

An electric circuit is a closed path through which electric current can flow. Electrical components such as transistors, resistors, capacitors, and inductors are utilized in these circuits. Electronic devices, including computers, are constructed from thousands of electric circuits composed of these electronic components.

What is oscillation?

You have already come across hundreds of oscillations in your daily life. The term “oscillation” refers to the repetitive to and fro motion of a device or quantity. When a particle oscillates, it vibrates about an equilibrium position periodically. Common examples of oscillation you might be familiar with include the pendulum of a clock, your heartbeat, and the movement of strings in musical instruments. The pendulum moves to and fro from its mean position. Similarly, in a slinky, the spring extends and contracts rhythmically. An oscillation can be represented using a sine wave, whose value itself oscillates about 0. Oscillations can be free, damped, or forced.

Inductor

An inductor is a passive electronic component that converts electrical energy into magnetic energy and stores it. It is made up of a coil of wire that is generally wrapped around a given core but can be made without a core as well. An inductor works on the principle of electromagnetic induction, which is related to the generation of a magnetic field due to a changing current. 

Since an inductor is in the form of a coil, when current going through it changes, the loops of the coil resist the corresponding change in magnetic field. A quantity that characterizes inductors is the inductance. It is defined as the ratio of induced EMF to the change in current over time. The figure below shows a few common inductor types:

Inductor types

The increase in current creates a magnetic field in the inductor. This magnetic field reduces when the current through it decreases and the energy stored in the magnetic field is converted into electrical energy. Thus, an inductor can store energy in the form of a magnetic field.

Capacitor

Capacitance is the ability to store electric charge and capacitors are devices that facilitate this. Generally, they are made of two conducting plates separated either by air or by some other dielectric material like ceramics, plastics, mica, etc. 

When a capacitor is connected to a DC source, electrons move from the negative terminal and accumulate on the conducting plate, inducing a positive charge on the other plate. The dielectric material in between the plates prevents electrons from crossing the barrier. This way, electrons get stored on the plates and the energy thus stored can be utilized later. Mathematically, capacitance is measured using the following formula:

The following diagram shows a capacitor:

Capacitor

LC oscillator

An LC circuit is so named because it contains an inductor and a capacitor. Capacitance is depicted by C while inductance is depicted by L, hence the name LC circuit. An LC circuit is also sometimes referred to as a tank circuit. An LC circuit can act as a resonator that stores energy and then oscillates at a particular frequency using positive feedback without external influence.

LC Oscillator

Working of LC oscillator

1. In the circuit depicted in the figure above, we have an inductor and capacitor connected in series.
2. When voltage is applied, the capacitor starts developing a charge. In this time period, the inductor does not receive anything.
3. When the applied voltage is removed, the energy stored in the capacitor flows to the inductor and the capacitor discharges.
4. Once the capacitor has been completely depleted, the inductor carries all the energy and it removes it into the circuit. This charges the capacitor in the opposite direction till all energy is transferred to it.
5. This cycle repeats to give rise to LC oscillations.

Applications

LC oscillators find a wide range of applications in electrical circuits. Here are a few examples.

1. They are used in AC-DC converters.
2. They are used in amplification circuits.
3. Radios, TVs, transmitters, filters, etc. all utilize LC circuits.
4. They are used for induction heating.
5. They are used in sine wave generators.

Summary

Capacitors store charge while inductors store magnetic energy. When connected in series, they can be used to create oscillator circuits which do not require external influence to operate. This article discussed concepts related to LC oscillator circuits in detail.

 

Frequently asked questions

1. What are free and forced oscillations?

Free oscillations occur when an oscillating body is allowed to oscillate without external influence. On the other hand, one can force a body to oscillate continuously using an external force, which is known as forced oscillations.

2. Differentiate between damped and undamped oscillation?

3. What are the applications of inductors?

Inductors find a wide range of applications, a few of which are:

1. Choking, blocking, filtering, or smoothening high frequency noise.
2. Used in oscillators.
3. Used in power converters.
4. Used in radios, TVs, wave generators, etc.

4. What are the differences between the capacitor and inductor?

5. What are the uses of capacitors?

1. Capacitors are used for quick release of electric charges. This is used in camera flashes, keyboards, etc.
2. Capacitors can be used to detect high frequency electromagnetic radiation.
3. Ignition systems use capacitors.
4. Oscillators, amplifiers, and transmitters utilize capacitors.

Introduction

In physics, there are two types of physical quantities: those that contain a direction as well as magnitude and those that contain only direction. The former are known as vector quantities and the latter are known as scalars. Time, temperature, mass, etc. are scalar quantities since there is no physical sense for mass to have direction. On the other hand, velocity, acceleration, force, etc. are quantities whose directions are important and thus, are examples of vectors.

The process of determining the magnitude and where applicable, the direction of a quantity is known as measurement. It yields a numerical value along with a direction if required. Measuring quantities also requires a standard set of units with reference to which, we can give their numerical value. For instance, we know our height to be 160 cm only because we have a reference value for how long 1 cm is. For this end, the SI system of units was developed to provide a global standard.

What is speed?

Speed measures the pace at which an object moves with reference to a reference point. When we talk of speed in physics, we are concerned with only the distance covered and do not inquire about the direction. Thus, speed is a scalar quantity. Mathematically, we can write:

In the SI system of units, speed is measured in m/s whereas the cgs system measures it in cm/s. Other common units include km/h, mph, etc.

Apart from moving in a straight path, objects can also move along a circular path in which case, we can measure their angular speed in terms of the angle they sweep out in a given time interval. Mathematically,

Types of speed

Physicists classify speed into various types depending on different criteria. Here are a few common classifications:

Uniform speed

An object is said to possess uniform speed if the speed remains constant in time. That is, even as time passes, its speed does not change.

Variable speed

Objects whose speed is not constant in time are said to be moving with a variable speed.

Average speed

We know that it is practically difficult for objects to keep moving at exactly the same speed over time. But over the course of a journey, one can calculate an average speed which gives us a general idea about the motion of the object. 

Average speed is measured by taking the total distance that the object covered and dividing it by the total time it took to cover that distance. That is,

Instantaneous speed:

As previously mentioned, an object may have different speeds at different instants in time. The value of its speed at an exactly defined moment in time is termed as its instantaneous speed at that moment.

The calculation for speed

To calculate an object’s speed, we can simply apply the formula for speed. Thus,

A few common examples of speeds measured by scientists include the speed of light in vacuum, which is approximately 3E8 m/s. On the other hand, the speed at which Earth rotates about its axis is 7.28E-5 rad/s and the speed at which it travels around the sun is given as 30 km/s.

Relation between angular speed and linear speed

We can derive a relation between the angular and linear speeds of an object. We know that linear speed is 

Further, we know that for circular motion, when the angle swept is very small, the arc length can be approximated as 

The angular speed is written as ⍵=θ/t. Hence, if we multiply both sides of this equation with r, we get:

Thus, angular and linear speeds are related by the equation v=r.

Solved examples

1. Raju drives at 15 km/h for 3 hours. How much distance did he cover?

We know that 

2. If the blade of a fan rotates at an angular speed of 16π rad/sec, what is the time taken for one complete rotation.

Angular speed can be directly related to the time taken for one complete rotation (T) as follows:

Hence, the fan completes one rotation in 0.125 seconds.

Summary

Speed is a scalar quantity that measures the pace at which an object is moving. It is measured by dividing the distance covered by the time taken to cover that distance. Angular and linear speeds can be related to each other.

Frequently asked questions

1. Describe Newton’s first law of motion.

Newton’s first law states that if an object is moving or at rest, it will continue in that state unless some external factor forces it to change its state of motion. Unless some external factor stops a ball from rolling, it will continue rolling.

2. How does the angular speed of an object remain the same at all points?

Angular speed measures the rate at which a certain amount of angle is swept by an object. It changes with radius and thus, remains the same for all points.

3. How does an ice skater control their angular speed?

Since angular speed depends on the radius, if the ice skater or ballet dancer pulls in their arm close to their body, they speed up. They can also reduce their speed by extending their arms. This is related to the law of conservation of angular momentum.

4. What instrument measures linear and angular speeds?

Linear speed is measured by speedometer in a car while angular speed is measured by an instrument known as tachometer.

5. What is the difference between speed and velocity?

Introduction

The Earth is the only planet in the solar system to support life and a major reason behind that is the air on this planet. Air is a mixture of gasses that surrounds the earth and contains oxygen, which is necessary for breathing. This blanket of air also acts as a protective shield against harmful radiation from outer space. Due to the presence of air and the force of gravity, there is a pressure of air all around us that is known as atmospheric pressure. It varies directly with height and is measured using a barometer. Differences in pressure lead to the flow of air and this leads to various weather phenomena.

What is a land breeze?

A land breeze is also called an offshore wind and occurs when wind blows from the land towards the sea. This process continues throughout the night and is reversed during the day. When the sun sets in the evening, the land cools down faster than the water, causing the air above it to cool down as well. However, the air above large water bodies doesn’t cool down as fast and thus, rises up, causing a low pressure zone. Due to this pressure difference, air starts moving towards the water, creating a land breeze.

Land breeze

What is a sea breeze?

When wind blows from the sea towards the land, it is known as a sea breeze or onshore breeze. This typically occurs during the daytime when the sun heats up the land more quickly than the water, causing the air above the land to warm up and rise. As a result, there is low pressure over the land. The air above the water, which is cooler, has a higher density, leading to high pressure. The pressure difference causes the air to move from the high-pressure area over the water to the low-pressure area over the land, creating the sea breeze.

Sea breeze

Facts about the land and sea breeze

Land Breeze Formation

1. Land cools down faster at night while water bodies retain heat for a longer period of time.
2. The higher temperature causes a low temperature zone above the water as compared to the area above land.
3. Hence, air starts flowing towards the sea, giving rise to the land breeze.

Sea breeze formation

1. During the day, the presence of sunlight heats up the land, causing the air above it to heat up and rise.
2. Water bodies don’t heat up as fast and thus, the land becomes a low pressure zone.
3. This creates a flow of air from the sea towards the land, known as a sea breeze.

Difference between land and sea breeze

While both land and sea breeze are most evident in coastal areas and affect weather conditions across an area of 32-50 km, they also carry some differences. These are tabulated below:

Summary

This article discussed how land and sea breeze are generated owing to the difference in temperatures and pressure over land and sea during night and day. It also listed a few salient points about the two and tabulated the differences between them. For better understanding, illustrative diagrams were also shown.

Frequently asked questions

1. What are atmospheric disturbances?

Atmospheric disturbances are temporary disturbances in the atmosphere of the earth that move from place to place. Depending on their strength, they can cause a drastic change in weather conditions even in a short period. Some examples include cyclones, hurricanes, and tornadoes.

2. What is a cyclone?

A cyclone is a swirling mass of air or wind that rotates either in clockwise or anticlockwise direction, depending on whether one is in the northern or the southern hemisphere. The center of the cyclone is at low pressure while the rotating portion is at a very high pressure.

3. What is the Coriolis effect?

Coriolis effect is a phenomenon that occurs due to the rotation of the Earth. It causes objects to appear to move in a curved path rather than a straight line when viewed from a rotating frame of reference. In the Northern Hemisphere, objects tend to curve to the right, while in the Southern Hemisphere, objects tend to curve to the left

4. What is wind?

Wind is simply the phenomenon of flow of air on Earth. Any type of movement of air is known as wind but depending on strength, wind can be a gentle breeze or a terrible tornado.

5. What are the effects of the Land breeze and sea breeze?

Land breeze leads to:

• Formation of fog above the sea.
• The heating of land at night.
• High humidity over the sea and dry conditions over the land

Sea breeze leads to:

• Early morning rainfalls.
• Humidity over the land.
• Clouds and fog over the land.

Introduction

In physics, we measure energy and work in units of Joule, one unit of which is equal to applying 1 Newton of force over a distance of 1 meter. In various objects, applying force or stress leads to the object heating up and the amount of heat produced is equal to the work done. On the other hand, in electrical circuits, it is the flow of current that leads to the generation of heat. The amount of heat generated in electrical circuits is directly proportional to the square of the current passing through them, the resistance of the circuit, and the time for which the current is made to flow. This relation is known as Joule’s law of heating. This article focuses on this law and discusses its concepts and applications.

What is Joule? 

Joule is a unit of measurement for both energy and work. It is defined as the work done by applying a force of one newton over a distance of one meter. When this occurs, one joule of energy is produced. Joule is equivalent to Newton meters. It is important to note that every time mechanical force is applied, an exact equivalent of heat is generated.

Joule’s law of heating

Joule’s law relates the heat generated in an electrical circuit to current, resistance, and time. It states that the heat generated in an electrical component varies directly with the square of the current, the resistance of the circuit, and the duration for which current flows in the equation. Mathematically,

James Joule discovered the equation for power dissipated by a resistor through empirical observation of power, current, and resistance measurements. He found that the power dissipated by a resistor is proportional to the square of the current passing through it. This process is known as Joule heating, where electrical energy is converted into heat by a resistance element. This theory applies to any electrical device designed to generate heat, such as electric heaters and toasters. Joule’s law and Ohm’s law were both discovered empirically by examining real-world data.

The dissipation of power in an electrical circuit simply means that due to the current flow, some power is lost in the form of heat. According to the law of conservation of energy, energy cannot vanish into nothingness. Instead, it is lost to the surroundings. This concept is also used in toasters and heaters. They contain heating elements which have a high wattage and thus, generate enormous amounts of heat. That heat is then radiated to the environment, heating up the room. 

We can derive Joule’s law as follows:

Using this formula, we have:

Joule heating power equation for AC and DC

The equation we have derived for calculating the heat generated in an electrical circuit is equally valid across AC and DC components. Thus, regardless of the nature of current, the heat generated is given by:

However, while dealing with AC components, the value of current becomes dependent on time.

Application of joule’s law of heating

1. Electric fuse

An electric fuse is a small piece of wire that is generally manufactured from a tin alloy and has a specific melting point. It is connected to electrical appliances in series and protects them from damage due to high current.

Electric fuse

When the current passing through the circuit crosses a threshold, the heat generated in the circuit increases the temperature of the fuse wire, which melts and thus, the connection is broken. Thus, the appliance remains safe. There are other applications of Joule’s law as well, which include:

• Electric heater
• Electric iron
• Electric geyser

Summary

Energy and work are measured in units of Joule. 1 J of work is done when an object is made to move a distance of 1 m by applying a force of 1 N. Joule is equivalent to Newton meters.

In electrical circuits, the flow of current leads to the generation of heat, which is related directly to the square of the current, the resistance, and time. This is known as Joule’s law of heating and in this article, we discussed this concept in detail.

Frequently Asked Questions

1. What are the variables that affect heat in a circuit?

As per Joule’s law, heat in a circuit depends on current, resistance, and time.

2. Which device doesn’t follow Joule’s law?

All electric circuits follow Joule’s law. However, in a number of situations, heat generation is an undesired side effect which must be minimized. On the other hand, devices like geysers and irons actually need heat generation.

3. Is the effect of joules heating reversible?

The heat energy dissipated in circuits can not be brought back by reversing the direction of current. That energy is lost to the environment.

4. Do ideal conductors also suffer from heating?

In theory, no. An ideal conductor is one whose resistance is zero and thus, the heat generated in an ideal conductor would be zero.

5. Does voltage change affect heat?

Yes. Changing the voltage applied to a circuit changes the current flowing across it and thus, the amount of heat generated changes.

Introduction

In the Friedel-Crafts reaction, an alkyl or acyl group swaps places with the hydrogen atom of an aromatic molecule to make a hydrocarbon or ketone. This is an example of an electrophilic substitution reaction. When an aromatic molecule is alkylated or acylated, an acid catalyst (Lewis acid) is present. This could be \(AlC{l_3}\), \(ZnC{l_3}\), or \(B{F_3}\). The attacking particle is an alkyl or acyl cation, which is made by the catalyst. In 1877 and 1878, J. Crafts and C. Friedel came up with this reaction. They used it to connect substituents to aromatic rings.

During the alkylation and acylation processes, the hydrogen atom that was originally attached to the aromatic ring is swapped for an electrophile. The most common catalyst is aluminium trichloride, which works as an acid (Lewis) by combining with chlorine to make a strong electrophile.

What is Friedel crafts reaction?

These reactions are organic coupling reactions that attach substituents to aromatic rings through an aromatic substitution that is electrophilic. During a typical Friedel–Crafts reaction, a new C–C bond is made. Friedel-Crafts processes can be either acylation or alkylation. A process called alkylation is used to add the benzene ring and a short carbon chain. When an acyl group is added in the process of acylation, aryl ketones are made.

What is its type

The two main categories of Friedel-Crafts processes are: 

• Friedel craft acylation
• Friedel crafts alkylation.

Friedel Craft Alkylation and Acylation

Friedel craft alkylation 

When there is an aromatic ring, Friedel Crafts alkylation is done by using a Lewis acid on an alkyl halide. While the C-H bond is being broken, the alkyl group joins the ring and forms a C-C bond. A Lewis acid catalyst like \(FeC{l_3}\) or \(AlC{l_3}\) is used in this reaction to speed up the removal of the halide and make a carbocation. Before the alkylation reaction can start, the resultant carbocation has to change its shape. You should never use alkenyl, alkynyl, or aryl halides; only an alkyl halogen (Cl, Br, or I) should be used, or the reaction won’t work. The carbocations of these species are hard to make and very unstable.

This is the main way that the industry makes high-octane fuels, surfactants, fragrances, antioxidants, etc., as well as other important goods like cumene and thymol.

Mechanism of Friedel craft alkylation 

STEP1: The lewis acid attavks the alkyl halide which results in the formation of a  carbocation. 

STEP2: The carbocation attacks the aromatic ring and an arenium ion is obtained.

STEP3: Deprotonation occurs at the ipso carbon and aromaticity the ring is restored and the alkylated aromatic molecule is obtained. The  \(AlC{l_3}\)  catalyst is renewed. 

Friedel craft acylation 

When a Lewis acid catalyst like \(AlC{l_3}\) is present, this aromatic electrophilic substitution reaction between arenes and acyl halogens or anhydrides and acyl halogens or anhydrides leads to the making of monoacylated compounds. The halogen in the acyl halide joins with the Lewis acid to form a complex. This makes a better electrophilic acylium cation (RCO+) that is stable through resonance. Ketones are the only thing that can come out of this process.

The Friedel Crafts acylation is an important business process. It is used to make fine chemicals, intermediates for making other chemicals, and chemical feedstock.

Mechanism of Friedel craft acylation 

STEP1: The acyla halide and the lewis acid catalyst complexate. \(AlC{l^{4-}}\), is removed and an acylium ion is formed (RCO+). 

STEP2: The acylium ion is an electrophile and it attacks the aromatic ring’ double bond  resulting in the formation of an arenium ion. 

STEP3: Deprotonation occurs at the ipso carbon and aromaticity the ring is restored and acylated aromatic molecule is obtained. The \(AlC{l_3}\),  catalyst is renewed. 

Summary 

“Friedel-Crafts alkylation” is the process of replacing an aromatic proton with an alkyl group. To do this, a carbocation is used to attack the aromatic ring in an electrophilic way. Alkyl halides are used as reactants in the Friedel-Crafts alkylation method, which makes alkylbenzenes. During Friedel Crafts acylation, when an acyl group is added, aryl ketones are made.

Friedel Crafts acylation is better than Friedel Crafts alkylation in a number of ways. One of these benefits is the ability to better control the reaction products. Another is that the acylium cation is stable because of resonance, which makes rearrangement impossible. The Clemmensen reduction process can be used to turn the produced ketones into alkyl groups.

 

Frequently Asked Questions

1. Why can we not uses lewis base aromatic compounds in Friedel-Crafts reactions?

We can’t use Lewis base organic compounds because \(AlC{l_3}\), which is used in the Friedel-Crafts process and is a Lewis acid catalyst, reacts with Lewis base to make salt. Because the base gets a positive charge, it can be used to stop other reactions from happening.

2. Can Friedel craft reaction take place without catalyst?

No, Friedel craft reactions can not take place without catalysts. For the Friedel Craft reaction to occur without catalyst, the finest aromatic reagent  are those that can produce the electrophile without needing Lewis acids. Since benzene rings are not strong nucleophiles, they can not produce electrophiles directly. Thus it needs an external help. 

3. What is arenium ion?

An arenium ion is a cyclohexadienyl cation in organic chemistry. It is a reactive intermediate in electrophilic aromatic substitution. Two hydrogen atoms that are attached to a single carbon atom are in a plane that is perpendicular to the benzene ring. The arenium ion is no longer an aromatic species, but due to delocalization, it is still pretty stable:

Introduction

Distillation is an isolation technique used to separate two miscible or immiscible liquids. This is based on the principle of boiling points of the components of the liquid mixture.  It has been used since ancient times to make oils, alcohol, beverages, etc. The distillation process has now been industrialised and made faster and more efficient with more delicate instrumentation. 

What is fractional distillation?

Fractional distillation is another form of the distillation process that makes it simple to separate two or more liquids in combination with different boiling points but near one another. Vaporization is the method used for this separation. The process continues, with the liquid having a lower boiling point evaporating first and emerging from the mixture. With a pressure of 1 atm, the liquids typically have boiling points that are dissimilar by around 25 °C. Separation benefits greatly from fractional distillation. Thus, it is frequently used in a variety of sectors, including cryogenic air separation, chemical plants, oil refineries, and many others. Distillation typically operates at a constant state.

Fractional Distillation

Principle of fractional distillation 

The difference in the boiling points (B.P.) of the mixture’s liquids serves as the foundation for the fractional distillation principle. The impurities contained there also exhibit distinct boiling temperatures when the same mixture is heated, making it simple to separate them using a pipe. Now, with the aid of an example or instance, we may comprehend this. One illustration is the fractional distillation of water and ethanol (C2H5OH). Considering ethanol’s boiling point is 78.5 °C and water’s boiling temperature is around 100 °C. As a result, the fractional distillation method may be used to separate the combination of these two liquids, as there is a sizable difference in their boiling points.

Difference between simple and fractional distillation

Fractional Distillation Apparatus

The fractionating column of the fractional distillation equipment increases its efficiency by giving the liquid more opportunities to condense or freeze, giving it an edge over a straightforward distillation procedure. In the fractional distillation process, a fractionating column packed with glass beads offers a large surface area for the vapours to clash and lose energy, allowing them to be condensed and distilled swiftly.

Fractional Distillation in industry.

The division of crude oil into its constituent parts is one of the most significant and often utilized instances of fractional distillation in industries. Due to the fact that crude oil is a mixture of several materials or components, such as diesel, paraffin wax, naphtha, gasoline, kerosene, and lubricating oil. The fractional distillation method is employed in industries to separate the aforementioned components. Many steps are taken to do this. The machine’s chamber is filled with crude oil, which is heated with high-pressure steam. Once the mixture begins to boil, its vapour is produced. The vapour phase now contains a variety of substances or components and the vapour increases. 

Summary

In the fractional distillation process, 2 or even more liquids with various boiling points that are close to one another in a combination may easily be separated. Vaporization is the method used for this separation. In this case, the liquid with a lower boiling point vaporizes first and separates from the mixture. The process then proceeds in a similar manner. With a pressure of 1 atm, the liquids typically have boiling points around 25 °C apart from one another. Nevertheless, simple distillation is utilized when the difference in temperature between the liquids is more than 25 °C. Separation benefits greatly from fractional distillation. Hence, it is frequently used in enterprises and refineries for oil and chemical facilities.

Frequently Asked Questions

1. Fractional distillation: Is it more precise?

Fractional distillation is more effective when the two liquids in combination have similar boiling points, often with a range not  exceeding 40 degrees Celsius. With one apparatus, fractional distillation completes several straightforward distillations.

2. What is low-temperature fractional distillation?

At low temperatures, Low-temperature fractional distillation is used to separate a mixture into its constituent elements. This method is often used for the separation of component elements that boil at less than 25°C apart under a hoover.

3. Why does the temperature rise in fractional distillation in the upward direction?

Vapours move through the fractionating column during distillation, releasing their heat energy to the walls of the column and condensing. This causes the column to become warmer. The bottom end of the column is more frequently traversed by the vapours than the top end.

Introduction

The electron (e-) is a particle of an atom, just as an atom is a substructure of matter. There is no way to create or destroy these atoms. Atoms were assumed to be the smallest unit of a particle before the discovery of electrons (e-). Tests used in the discovery of the electron shed light on some of the atomic basic features (e-). It was a major turning point in physics when the electron (e-) was discovered as the first subatomic particle. It turns out to be one of the most crucial in modern chemistry and physics for defining the chemical bond.

Thomson Cathode Ray Experiment

J.J. Thomson (J.J.T.), a physicist, studied CRTs (cathode ray tubes) in the early 1990s (CRT). A glass tube, sealed under vacuum, is present. Particles are accelerated from the cathode to the anode as a high voltage is supplied between two electrodes on one side of the tube.

Cathode-ray tubes get its name from the fact that the cathode is the point of genesis for the particle beam (CRT). Phosphors produce a spark or light when hit by the beam. Thomson investigated the particles’ properties by surrounding the beam with two electric plates that were charged in the opposite direction. A positive electric plate was used to deflect the beam away from a negatively charged one. This means that the particles in the beam were all electronegative.

He also found that the magnetic field could be used to redirect the beam by placing magnets on each side of the tube. After calculating the mass-to-charge ratio of beam particles, he conducted an experiment showing that the mass of a single particle was far less than that of any known atom. Cathode Ray (CR) attributes were the same and irrespective of cathode composition, he found after conducting more tests using metallic elements as electrode components. The following conclusions were then made:

1. Components of the cathode ray are all of the negative variety.
2. Particles must have been part of the atom, as their combined mass is 1 x 2000 that of a single hydrogen atom.
3. Every atomic nuclei have the potential to contain these subatomic particles.

His findings were originally controversial, but experts gradually accepted them. This cathode ray (CR) particles were subsequently referred to as electrons (e–). 

Cathode Ray Experiment

Define Electrons

The electron (e-) is a negatively charged subatomic particle with a small mass. Consequently, it may be readily deflected by approaching another e- or the positive nucleus of an atom. The discovery of this primary building block came first. These are fundamental particles with a negative one-charge. An e- has the same negative charge as a proton (but has an opposite sign).

While protons and e– have the same charge magnitudes, the former is substantially smaller and lighter than the latter. An e- is a particle with a negative charge. The negative charge is  \(1.602 \times {10^{ – 19}}\)  Coulomb in magnitude. The mass of an e- is just 1/1837 that of a proton.

Electron density: The mass of one electron is \(9.10938356 \times {10^{ – 31}}kg\)kilograms (e-).  As compared to the mass of a proton, the mass of an electron (e–) is extremely small.

Properties of Electrons

Following are the properties of electrons:

1. The positively charged protons and neutrons make up the nucleus of an atom, while the negatively charged electrons orbit around it.
2. Electrons are the sole fundamental component of an atom that cannot be further split into smaller subatomic particles like protons and neutrons. The letters e or e- stand for them in the alphabet.
3. It is possible to raise the energy level of an electron by absorbing some of its lower energy level.
4. Due to their extremely low mass of 9.10941031 kg, electrons do not contribute to an atom’s total mass.
5. A proton has a positive electric charge of +1, whereas an e- has a negative charge of -1.
6. The attraction between the negative charge of the electron and the positive charge of the protons causes the electron to go in a certain orbit around the nucleus.

Electrons and Compounds

The electron was discovered in 1897. The discovery of the proton between 1911 and 1919 and the neutron in 1932, however, recast the electron’s meaning and significance. The whole concept of atomic structure was established with the discovery of the other two subatomic particles.

The nucleus of an atom is composed of positively charged subatomic particles called protons. The number of protons in an atom and the size of an electron are both element-specific. For comparison, oxygen (O) has 8 protons and carbon (C) has 6, but hydrogen (H) has just 1.

Rutherford postulated neutrons before discovering the proton; Chadwick confirmed their existence in 1932. As neutrons have no net electric charge, they were appropriately named. All elements in the periodic table are made up of neutrons except hydrogen (H). A neutron’s mass is somewhat more than that of a proton.

Summary

Electrons were first identified as particles in cathode rays, discovered by J.J. Thomson, whose discoveries were widely accepted. As a result of his research, a revised model of the atom’s structure was created. The electron’s charge was first determined by American scientist Robert Millikan. Using electrically charged oil droplets, he determined the charge on a single electron. He determined that the charge of a single e- is  \(1.602 \times {10^{ – 19}}\)  Coulomb. Millikan determined the electron’s mass by calculating its charge and utilising J.J. Thomson’s mass-to-charge ratio. The mass of an electron is  \(9.1094 \times {10^{ – 31}}kg\)  kg. In 1906, his discovery of the electron earned him the Nobel Prize in Physics.

Frequently Asked Questions

1. Why do electrons have a “negative” charge?

As electrons repel an electric field, the negative connotation is derived from this fact. By convention, a negative charge is assigned when an electron moves from the negative to the positive pole of an electric field.

2. How are electrons able to travel about?

When an electric voltage is applied, an electric field is created within the metal. This electric field causes the flow of electrons, which causes the electrons to migrate from one end of the conductor to the other end. The electrons will migrate towards the positive side of the charged object.

3. Do cathode rays have the ability to go through glass?

Cathode rays are not visible to the human eye, but when they strike the glass wall of an early hoover tube, they excite the atoms there, which in turn causes the atoms to fluoresce, another name for the emission of light.

Introduction

John Dalton, an English philosopher and scientist, established the atomic notion in 1808 as part of his investigation of the molecular structure of matter. It asserted that everything is made up of atoms, which are supposedly tiny autonomous creatures. According to Dalton’s atomic theory, the constituent parts of these substances are atoms that cannot be broken down into smaller parts. These other elements’ atoms range in size and mass, whereas those of a particular element are nearly uniform.

John Dalton

Dalton’s Atomic Model

Indeed, matter studies have been among the most fruitful areas for scientists. Both scientists and philosophers have spent years trying to make the world easier to grasp. The properties, structure, and other characteristics of matter’s fundamental particles have long piqued the interest of scientists. Hence, several atomic theories have emerged. The idea that matter comprises smaller units, or “particles,” is credited to Democritus. Such tiny things have been given the Greek word for “indivisible” and “atom” as their name. Democritus’ Atomic Theory rests on this principle. As a result, technological infrastructure needed to be improved, and scholars knew very little about this concept then. John Dalton, a scholar from around 2,000 years ago, displayed their attempts to simplify the situation. John Dalton published his now-famous atomic theory in 1808. This hypothesis was first given by John in a paper he named “A New Chemical Philosophy,” and at the time, it was novel. Dalton’s theory revolved around two laws:

1. Law of Conservation of Mass: Antoine Laurent Lavoisier developed the principle of mass conservation in 1789. Although the creation and destruction of matter are prohibited by law, matter can transform into another form within a closed system. Scientists use this rule to preserve linear equations.
2. Law of Constant Composition:  The rule of constant composition states that a pure material always has the same number of elements. For example, the sodium and chlorine content of NaCl, the chemical formula for table salt, remains constant regardless of how much salt we manufacture.

Postulates of Dalton’s Atomic Theory

Following are the postulates of Dalton’s Atomic Theory

• All matter is composed of tiny atoms and interconnected particles.
• There is no difference in mass, size, or any other physical property between iotas of different substances. Yet, due to their different characteristics, the mass and size of particles composed of different elements can vary widely.
• It was impossible to create or destroy an atom. Yet, iotas can’t be broken up into smaller pieces.
• Atoms of various elements mix in fixed, whole-number proportions to produce compounds.
• In compound reactions, atoms might undergo transformations, form bonds, and break free.

Merits of Dalton’s Atomic theory

Some of the key advantages of the theory are:

• It provides a basic idea for telling the difference between elements and compounds.
• Several proportional rules, mass conservation, and stable proportions are all upheld.

Limitations of Dalton’s Atomic Theory

Some of the key advantages of the theory are:

• Such an atom has been repeatedly proven to be divisible. Neutrons, protons, and electrons are the three possible constituents of an atom. Remember, though, that the smallest thing that may participate in a chemical reaction is one atom.
• According to Dalton’s atomic theory, all atoms of a given element have the same mass, size, and chemical and physical properties. The density and mass of atoms are both visible differences across elements. Isotopes are different varieties of an element that have different masses. The mass numbers of the two stable isotopes of Cl are 35 and 37, respectively.
• In addition, atoms of different elements have different sizes, masses, and other chemical and physical properties. That’s not always the case, though. For example, the atomic mass of an Ar or Ca atom is 40 amu. Atoms with the same mass number form an isobar.
• According to Dalton’s atomic theory, chemical compounds are generated when different constituents mix in simple whole-number proportions. Yet, this might not be the case with more complicated chemical compounds.
• In Dalton’s atomic theory, allotropes are not accounted for. The Dalton atomic hypothesis can no longer explain the observed differences in properties among charcoal, graphite, and diamond.
• According to Dalton’s atomic theory, the atom is the smallest unit capable of participating in a chemical reaction. Several of the underlying assumptions of this theory remain valid in modern chemistry. The proposed model of atomic structure represents a significant advance in chemical theory. It’s what modern atomic theories and quantum mechanics are built on.

Influences on Modern Atomic Theory

Many advances in modern atomic theory may be traced back to Dalton’s atomic theory. Dalton’s method was not only innovative for its day, but it also served as a foundation for subsequent chemists. Ernest Rutherford, Chadwick, Niels Bohr, JJ Thompson, and others after Dalton all made important contributions to the development of atomic theory. Eventually, JJ Thompson identified electrons, and Rutherford honed the hypothesis to pinpoint the nucleus. The atomic model as we know it today is thus a product of both Niels Bohr’s model and the Quantum mechanical model. Although the field of atomic theory has progressed much over the past two centuries, much of Dalton’s original framework remains.

Summary

Our analysis leads us to the conclusion that this concept represents John Dalton’s atomic model from 1808. According to Dalton, atoms are the fundamental building blocks of all matter. It also suggests that the different masses of atoms belonging to different elements are unaffected by chemical reactions. They wondered what the fundamental particles were like, how they were put together, and what properties they had. This led to the growth of several atomic theories. It would appear that the smallest unit of a substance that may take part in a chemical reaction is the atom. Even within the same element, atoms may have different masses. Dalton’s postulates for the atomic theory do not include this. This is a flaw in some theoretical frameworks.

Frequently Asked Questions

1. How does the presence of subatomic particles lead to the failure of Dalton’s atomic theory?

Thomson’s discoveries on subatomic particles were groundbreaking. This proved Dalton wrong when he claimed such atoms are the smallest possible material component. Thomson concluded from his findings that electrons are fundamental building blocks of atoms.

2. Which is the latest atomic model?

The electron cloud model is one of the most sophisticated and well-known current atomic models. Although it retains the nucleus concept from Bohr and Rutherford’s models, it provides a new description of electron velocity around the nucleus.

3. What gas makes up the cathode ray tube?

Hydrogen gas, the lightest gas (perhaps the lightest element) on ionisation, yields the highest charge value to the mass ratio (e / m ratio = \(1.76 \times {10^{11}}\) coulombs per kg), hence it is often used in cathode tube experiments.

Introduction 

When a phone is hooked to its charger, how does the battery work? How does the cell in a TV remote control work? All of these questions have been thoroughly explored in the scientific discipline of electrochemistry. Electrochemistry is the study of both the creation of electricity through chemical processes and the use of electricity to conduct non-spontaneous chemical reactions. The task is accomplished by using cells. Cells are the building blocks that trigger chemical processes that produce or generate electricity.

Types of cells

There are two types of cells:

1. Electrochemical cell: An electrochemical cell is a device that may produce electricity through chemical processes that occur naturally. The chemical reactions occurring here are called redox reactions. During redox reactions, electrons are exchanged between different chemical species. Galvanic or voltaic cells are other names for these devices. One type of electrochemical cell is the Daniell cell.
2. Electrolytic cell: Electrolytic cells are a subset of electrochemical cells that are capable of using electrical energy to catalyse chemical processes. That is to say; electricity needs to come from somewhere else. Then, an artificial reaction can be initiated. Electrolytic cells have traditionally been used for the electrolysis of substances.

Difference between electrochemical cells and electrolytic cells

Cell structure 

There are two electrodes in a cell: the cathode (positive) and the anode (negative) (-ve terminal). Submerge both electrodes in the corresponding metal salt solutions. The anode of an electrochemical cell is also known as the oxidation half-cell because of the chemical process that takes place there. The cathode is the decreased half-cell, another name for it. Connecting the two electrodes is a salt bridge, a U-shaped tube filled with gel and an electrolyte.

Daniel Cell Diagram

What is a Daniell cell?

An electrochemical cell known as a Daniell cell is used to transform chemical energy into electrical power. The cell undergoes a number of chemical processes in order to produce electricity. Electrodes made of zinc (Zn) and copper (Cu) are used as the anode and cathode in a Daniell cell. The salt solutions have been poured over the metals.

In a Daniell Cell, the anode is composed of zinc (Zn), while the cathode is composed of copper (Cu). There is still a chemical solution containing ions bathing both electrodes. The proper chemicals are copper sulphate and zinc sulphate. It improves the voltaic cell, using its copper and zinc electrodes to produce a 1.1 V potential difference. The cell supplies energy to the circuit after electrons are produced at the anode and transferred to the cathode.

Daniell cell chemical reaction 

The following chemical reactions take place in Daniell cell:

\(Zn\left( s \right) + C{u^{2 + }}\left( {aq} \right) \to Z{n^{2 + }}\left( {aq} \right) + Cu\left( s \right)\)

Reaction at the anode:

\(Zn\left( s \right) \to Z{n^{2 + {\rm{ }}}}\left( {aq} \right) + 2{e^ – }\;\;\;\)

Reaction at the cathode:

\(C{u^{2 + }} + 2{e^ – } \to Cu\left( s \right)\;\;\;\)

Daniell cell working 

In the Daniell Cell, \(CuS{O_4}\) and \({H_2}S{O_4}\)are stored in a copper container until needed. The components of its operating system are:

• A zinc rod that has crystallised in the zinc sulphate solution may be seen (\(Z{n_2}S{O_4}\)).
• A see-through layer underneath the copper container keeps the \(CuS{{O}_{4}}\) crystals and solution in touch. As a consequence, solution saturation is maintained.
• An electric current is produced by the external circuit.
• Mass is gained by the copper rod and lost by the zinc rod.
• Zinc sulphate concentration rises as Copper sulphate decreases.
• Both methods maintain their electrical neutrality.

Daniell cell representation 

The Daneil cell is represented as:

\(Zn{\rm{ }}\left| {{\rm{ }}Z{n^{2 + }}\left( {aq} \right){\rm{ }}} \right|{\rm{ }}\left| {{\rm{ }}C{u^{2 + }}\left( {aq} \right){\rm{ }}} \right|{\rm{ }}Cu\)

The symbol “| |” represent the salt bridge, the right side represents the reduction half-cell, and the left side refers to the oxidation half-cell.   

Application of Daniell cell 

Some of the applications of daniel’s cell are: 

• Used for making batteries, which are essentially just groups of cells in series.
• Creating electricity while minimizing electrical consumption.
• Telepathy through inductive coupling

Summary 

Certain electrochemical cells function in an electrolytic fashion. Hence, the electrolytic cell has everything that would normally be present in an electrochemical cell. Both electrochemical and electrolytic cells rely on the transport of electrons throughout the system to carry out their functions. Whereas electrolytic cells undergo non-spontaneous chemical reactions, electrochemical cells undergo chemical reactions of their own accord. To put it another way, an electrochemical cell is not the same as an electrolytic cell.

 

Frequently Asked Questions

1. What is a rechargeable cell?

Rechargeable batteries can only be made from secondary cells, which undergo reversible chemical processes. a cell that generates an electrical current, but whose chemical activity may be reversed by delivering a current in the opposite direction through the cell.

2. What maintains the electrical neutrality in a cell?

The Salt Bridge is responsible for preserving charge neutrality in the Daniell cell’s two compartments.  It is a glass tube which  contributes to keeping the balance of the charge.

3. Why are the charges of electrodes different in Daniel cell?

Daniel cell is an electrochemical cell whose anode has a negative potential with the solution. Which makes it negatively charged. The removal of the metals from the anode during oxidation causes a buildup of electrons upon that anode, which gradually turns it negative. Eliminating metal ions from the electrolyte results in the consumption of electrons, which turns the cathode positive.