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Introduction

The terms nucleophile and electrophile were coined by Christopher Kelk Ingold in 1933 to replace A. J. Lapworth’s anionic and cationic terminology. The term “electrophile” is a result of merging the words “electro,” denoting electrons, and “philes,” indicating a sentimental attachment. The word nucleophile comes from the combination of the Greek word ‘Philos,’ which means buddy, and the word nucleus. The field of chemistry relies heavily on these two concepts. Many organic reactions rely on the presence of these chemical substances. Electrophiles and nucleophiles, whose opposing behaviour is the impetus for many chemical processes, are well-known entities. Thus, it is clear that these definitions are crucial for a full comprehension of chemical processes.

Overview of Nucleophiles

Chemical species known as nucleophiles are able to give up a pair of electrons. They give up electrons because they are a species with an abundance of electrons. The word nucleophiles can be broken down into its component parts to denote any species that shows a preference for the nucleus. They are referred to be Lewis bases because of their ability to donate the pair of electrons they already possess. Lone-pair-of-electron species and negatively charged species are examples of neutral species. These chemical species are the ones that give up their pair of electrons during a chemical reaction, resulting in the creation of covalent bonds.

Nucleophilicity, which is comparable to the term basicity, describes the degree to which specific nucleophiles can transfer the pair of electrons. The element ammonia is a good example of a nucleophile because it has an unpaired electron.

Examples of Nucleophiles

As nucleophiles are negatively charged or they are species that contain lone pair of electrons. Some examples of nucleophiles can be given as, 

• All the halogen anions,\(B{r^ – },C{l^ – },{I^ – }\)
• Cyanide,\(C{N^ – }\)
• Ammonia, \({NH_3}\)
• Hydroxide ion

Structure of hydroxide ion

Features of Nucleophiles

This section elaborates on some of the key characteristics that nucleophiles must process.

1. There must be a net negative charge on a nucleophile, or it must have a lone pair of electrons if it is an electrically neutral species. Therefore, nucleophiles are typically anions.
2. A decreased electronegativity is required of nucleophiles in order for them to donate electron pairs effectively, so that they can be considered an inventive nucleophile. As a result, nucleophiles are often composed of less electronegative species.
3. The strength of nucleophiles can be affected by the solvent used in a chemical reaction, especially if the solvent is polar or protic and acts upon the nucleophiles.
4. Polar solvents can create hydrogen bonds with nucleophiles’ lone pairs of electrons, decreasing the likelihood that the nucleophiles will donate their electrons to other molecules.
5. The rate of nucleophilic reactions can be slowed if nucleophiles are sterically hindered. 

Overview of Electrophiles

Chemical substances having electron deficiency are called electrophiles. As a result, it attracts electrons towards itself since it has high electronic efficiency.

Two individual words, “electro” and “philes,” make up the phrase “electrophiles.” Electrophiles is a compound term that means “electron-loving species.” These substances might be either positively or neutrally charged chemical species. These compounds will take part in addition and substitution processes involving electrophiles. When they like interacting with a partner electron, electrophiles are referred to be Lewis acids. For this reason, the creation of a covalent bond is contingent upon the presence of these chemical species, which are able to accept a pair of electrons as part of a chemical reaction.

Examples of Electrophiles

Features of Electrophiles

We’ll go through what makes a good electrophile, and what makes a bad one, in more depth below.

1. In order to accept electrons from reacting nucleophiles, an electrophile must be positively charged or have an unoccupied orbital.
2. To attract electrons, an electrophile needs to have a weak link, hence electrophiles typically have weak polar bonds.
3. Because of steric hindrance, electrons cannot be transferred to electrophiles if they are too close to other electrophiles. Thus, an electrophile should not be sterically hindered. 

Difference Between Electrophiles and Nucleophiles

Some of the differences between electrophiles and nucleophiles are tabulated in the following table.

Summary

Chemical reactions take place by the donation and acceptance of electrons from one species to another species. Electrophiles and nucleophiles are two important chemical species that are necessary to undergo a chemical reaction. Electrophiles are the species that are positively charged or it a container back in the orbital to acceptive electrons. While nucleophiles are the chemical species that negatively charge lone pair of electrons so that they can donate this pair of electrons to another species. Some of the examples of electrophiles are \({BF_3}\) ,\({AlCl_3}\)

etc. And examples of nucleophiles are, \(C{N^ – },O{H^ – }\), etc. The important features of electrophiles and nucleophiles are affected by factors such as charge, electronegativity, steric hindrance, etc.

 

Frequently Asked Questions

1. Which of the following is the most powerful nucleophile in a nonpolar solution: I, Br, Cl, or F? 

Ans. Since the strength of a nucleophile increases with increasing electronegativity in nonpolar solutions, fluorine (F) is the most potent nucleophile in such a medium. As far as electronegativity goes, fluorine is the winner. That’s why it’s the strongest nucleophile there is.

2. What is the effect of solvent on nucleophilicity of a molecule?

Ans. Nucleophilic replacements benefit from more polar solvents since the nucleophile is generally an ionic molecule and needs to be dissolved in a polar solvent. Ions may be more stable in polar solvents than in others.

3. Why is \({BH_3}\) an electrophile?

Ans. \({BH_3}\) is an electrophile since the boron atom has an empty p orbital and an electron deficiency. Thus it easily acts as an electrophile. 

Introduction

An atom is the smallest unit of matter that preserves all the features of its element, while a molecule is a compound made up of numerous bonded atoms. Atoms and molecules are related, notwithstanding their differences. Atoms are the smallest unit of matter, while molecules are made up of several atoms, therefore they are clearly different from one another. A tomos, from the Greek a-tomos, means “indivisible,” which is apt because atoms are indivisible. Therefore, molecules can be further divided but atoms cannot.

Definition of Atom

Elements can be identified by their unique atoms, which are stable and resistant to chemical breakdown. Atoms typically consist of a nucleus composed of neutral protons and neutrons, with electrons carrying negative charges and circling the nucleus. The size of an atom is dependent on its number of protons and neutrons, as well as the existence or absence of electrons. The typical size of an atom is around 100 picometers, or 1/10 billionth of a metre. Nucleus mass is virtually entirely due to protons and neutrons because electrons contribute so little.

 Atomic Structure

Features of atom on the bases of modern atomic theory 

1. The term “modern atomic theory” is used to describe the most up-to-date, canonical explanation of atoms.
2. According to the foundations of atomic theory, atoms are the smallest units of chemical matter. They are the most basic building blocks of chemistry; they cannot be broken down any more.
3. Each element has its own distinct atomic structure, which differs from that of every other element.
4. Although, atoms can break down into much smaller particles. The nucleus of every element contains the same amount of protons, which are positively charged subatomic particles.
5. Neutrons are also present in the nucleus, albeit the exact number varies amongst isotopes of the same atomic type.
6. There are two types of atoms in the universe: isotopes, which have a varied number of neutrons but the same number of protons. For example, whereas all hydrogen atoms share a single proton, hydrogen-2 also has a neutron while hydrogen-1 does not.

 Proton, electron and neutron

Introduction of Molecule

Atoms of a molecule are held together in a certain configuration by chemical bonds. A molecule, like\({O_2}\), can consist of two or more atoms of the same element or of atoms from different elements. The properties of a chemical depend on the arrangements of its atoms within its molecule. The molecular weight is comparable to the sum of the atomic weights of the molecule’s constituent elements.

Bonding in Atoms

A molecule will be formed by bonding of two or more atoms. The atomic bonding is of several types such as:

Ionic bond

By sharing electrons between atoms, an ionic bond is formed. An ionically bonded substance is salt (NaCl), for instance. One of sodium’s outermost electrons is given up to chlorine so that the latter can finish filling its shell.

Covalent bond

To form a covalent bond, two or more atoms must share electrons from their outermost shell. Polymers are an example of materials that use covalent bonding. Polymers typically consist of long chains of hydrogen and carbon atoms connected via covalent bonds.

Metallic bond

When the electrons in the outermost shell are not paired with any particular atom or ion but instead exist as a “cloud” of electrons surrounding the ion centres, a metallic bond is formed. Magnesium, sodium, and aluminium are all examples of elements that form metallic bonds.

Difference between Atoms and Molecules

Summary

According to scientific consensus, the smallest unit of an element that can or cannot exist freely is an atom. Instead, the smallest unit of a compound is a molecule, which consists of a collection of atoms bound together by chemical forces. It’s possible for an atom to be either free or bound. To be sure, molecules exist in a liberated form as well. Aside from that, an atom has a nucleus filled with protons and neutrons and electrons around it. Conversely, molecules are made up of two or more atoms that are chemically bound together and may share some or all of their properties.

 

Frequently Asked Questions 

1. Are there no forces of attraction between the molecules of inert gases?

Ans. Inert gases have stable molecules that are not attracted to one another by electrostatic forces but do have weak van der Waals attractions and London dispersion forces.

2. Is  polar bond an ionic bond ?

Ans. No, a polar bond is not an ionic bond. It is a  specific kind of covalent bond which is formed between an electronegative and an electropositive atom .

3. What is the difference between positron and electron?

Ans. Electrons having the opposite chirality or quantum spin are called Positrons. The polarity of the electric charge is reversed since the spin is anticlockwise. Electrons are found inside an atom while positrons are not.

Introduction

Everything in the universe consists of tiny particles called molecules, which are classified based on the distance and the attractive force between their constituents. Different substances have distinct properties such as mass, temperature, density, volume, pressure, etc. 

The process of transfer of heat is achieved through three different processes in matter, namely, conduction, convection, and radiation. It is studied under thermodynamics, which deals with thermal energy and its relationship to heat, work, temperature, energy, entropy, and other physical properties of matter. 

Isotherms and adiabats

Thermodynamic system

A thermodynamic system is defined as a collection of matter confined within specific boundaries. Within the system, transformations can take place internally. At the same time, interaction with the outside world can occur through the boundaries, which can have a definite permeability. 

Based on the type of the boundary of the thermodynamic system, it can be classified into three categories: isolated system, closed system, and open system. 

• In an isolated system, no energy or matter is exchanged across its boundaries, and no work is performed. An example is items packed in a vacuum bag.
• A closed system allows for energy transformation, but matter cannot cross its boundaries, as seen in a cylinder closed by a valve. 
• And finally, an open system allows for the free exchange of energy and matter across its boundaries, such as a pool filled with water.

Thermodynamic processes

Thermodynamic processes involve an energy transfer between two systems or between systems and their surroundings, resulting in changes in volume, pressure, or temperature. Depending on the type of process, the process can change the energy of the system and perform some work on or by the system.

To classify thermodynamic processes, we look at how they are performed and what conditions they are performed in. 

• An isothermal process is one where the temperature of the system remains constant while energy is exchanged in or out.
• An isobaric process keeps the pressure constant.
• An isochoric process occurs when there is no change in the volume of the system.
• Finally, in an adiabatic process, no heat is exchanged by the systems. We’ll discuss adiabatic processes in detail here.

What is an adiabatic process?

An adiabatic process refers to a thermodynamic process in which, no heat energy is exchanged between the system and the surroundings. To be considered adiabatic, the system must satisfy two conditions.

1. It must be completely isolated. 
2. The process must occur over a short enough time frame, which makes it impossible for heat transfer to take place. 

Work done in adiabatic process

We start with a cylinder with walls made up of an insulating material. We assume that it has a frictionless piston attached to it also made up of an insulating material, effectively preventing heat from escaping. 

Reversible adiabatic process

An adiabatic process is considered reversible if the system can go back to its original state with no alterations. However, this can’t be achieved practically since a reversible adiabatic process does not really exist in nature. But theoretically, such a process is known as an isentropic process and one example of such a process is the adiabatic expansion of a real gas.

Irreversible adiabatic process

If the system cannot return to its original state after the process has occurred, the process is termed irreversible and is accompanied by a change in the entropy of the system. One example would be heat transfer.

Application of adiabatic process

Adiabatic processes occur in the following scenarios:

1. The principle is used in refrigerators.
2. Some processes in a thermal engine are adiabatic in nature. 
3. Compressors and turbines also work on adiabatic principles. 
4. Igloos and thermos flasks are isolated systems and they utilise adiabatic principles.
5. Quantum harmonic oscillators work adiabatically.

Carnot cycle

Summary

This tutorial covered the topic of thermodynamic systems and processes, including the work done in adiabatic processes. The discussion also included the differences between reversible and irreversible adiabatic processes and the various applications of adiabatic processes.

Frequently Asked Questions

1. Give some examples for all thermodynamic processes.

There are four types of thermodynamic processes: isothermal, adiabatic, isobaric, and isochoric. Some examples of these processes include boiling water, refrigeration, the Carnot engine, heat pumps, the freezing of water into ice, pressure cooking, and vertical atmospheric airflow.

2. Differentiate isothermal and adiabatic processes.

3. What is the specific heat capacity?

The specific heat capacity refers to the amount of energy that must be supplied to one mole of a substance to increase its temperature by one degree.

4. What do adiabatic compression and expansion do?

Adiabatic compression leads to an increase in system temperature and adiabatic expansion causes a decrease in temperature.

5. What is the first law of thermodynamics?

The first law relates the internal energy of the system with the heat exchange the work done. According to the first law, internal energy is the difference of the latter two quantities.

Also Read: Adiabatic Processes Derivation

Introduction

In thermodynamics, we explore various variables, including temperature, pressure, volume, entropy, heat, etc. These variables form the foundation for thermodynamic processes, which may be classified into isothermal, isobaric, adiabatic processes, etc. 

In an adiabatic process, thermodynamic variables can change value so long as no exchange of heat occurs. There are two critical requirements for such a process to occur:

1. The walls of the piston must be sealed to prevent heat exchange between the system and the environment. 
2. The process of compression or expansion must be completed rapidly.

 

Adiabatic processes

Derivation of adiabatic process formula

Adiabatic Relations between P, V, and T

The first law of thermodynamics gives rise to the conservation of energy, forbidding it from being created or destroyed.

 

Adiabatic relation between P and V

As per the first law, the change in heat energy is equal to the sum of the change in internal energy and the work done. That is,

Adiabatic relation between P and T

We again start with a mole of an ideal gas. Then, from the ideal gas equation,

 Adiabatic relation between V and T:

Examples of Adiabatic Process

1. An ice-box prevents heat from entering the system and thus, is an adiabatic system.
2. Hot water kept in a thermal flask is an example of an adiabatic system.
3. When warm air rises from the Earth’s surface, it expands adiabatically. As a result, the water vapour cools and condenses into water droplets forming a cloud.
4. A gas being compressed or undergoing rapid expansion is an adiabatic process since there isn’t enough time for heat exchange to occur.

Adiabatic Expansion

Adiabatic expansion is defined as a perfect condition for a confined system, where the pressure remains constant, and the temperature decreases.

Work done in an adiabatic expansion process

To derive the formula for work done, we start with a closed cylinder that contains n moles of an ideal gas. If P represents the pressure of this gas, and the piston in the cylinder moves up by a distance x, the work done by the gas may be written as:

Adiabatic work done

Description: The work done in an adiabatic process is the area under the curve

Here, A represents the cross-sectional area of the piston and dV = Adx is the increase in volume due to the piston’s movement. Suppose the initial and final stages of the system are \(\;({{\bf{P}}_1},{{\bf{V}}_1},{{\bf{T}}_1}){\bf{and}}({{\bf{P}}_2},{{\bf{V}}_2},{{\bf{T}}_3})\), respectively. Then the total work done is:

Shown above is the equation for the work done in an adiabatic process for a system consisting of n moles of an ideal gas. When the gas does work during adiabatic expansion, the work done is positive and the temperature of the gas decreases\(\left( {{T_2} < {T_1}} \right)\). Conversely, when work is done on the gas during adiabatic compression, the work done is negative and the temperature of the gas increases \(\left( {{T_2} > {T_1}} \right)\)

.

Adiabatic Compression

Adiabatic compression is a process wherein, a system undergoes compression without exchange of heat with its surroundings. It leads to an increase in temperature and a decrease in volume.

Adiabatic-reversible and irreversible process

Reversible adiabatic process: An adiabatic process is said to be reversible if the system can revert back to its original state after the process has taken place. Such a process isn’t possible in nature.

Irreversible process: An irreversible adiabatic process is one that cannot be reversed. It is accompanied by an increase in entropy and all real adiabatic processes are irreversible.

Conclusion

An adiabatic process is characterized by changes in the pressure, volume, and temperature of a system, but with no exchange of heat taking place between the system and its surroundings. For an adiabatic process to occur, certain conditions must be met: the walls of the container must be insulated, and the speed of compression or expansion must be rapid enough to prevent heat exchange.

For an adiabatic process, the relation between pressure and volume is \(P{V^\gamma } = \kappa \). This equation may be rewritten in terms of pressure and temperature as\({P^{1 – \gamma }}{T^\gamma } = {\rm{constant}}\), or in terms of volume and temperature as \({\rm{T}}{{\rm{V}}^{\gamma  – 1}} = {\rm{constant}}\)

The work done for an adiabatic process is given by the following expression:

Wadia = nR-1 T1 – T2

 

Frequently Asked Questions

1. The adiabatic process occurs at rapid rate. Explain why?

If the process were to occur slowly, it would give the system time to exchange heat, which would make the process non-adiabatic.

2. During the Adiabatic expansion, the temperature of gas gets lowered. why?

During adiabatic expansion, work is done by the system, causing a decrease in its internal energy. This lowers its temperature.

3.Difference between the Adiabatic and Isothermal processes?

4. Is the work done in an Adiabatic process change depending on which physical quantity?

5.  In adiabatic expansion, how the internal energy is affected? 

 

 

 

Introduction

In scientific measurements, it is impossible to achieve perfection and obtain error-free results. Every experiment will have some degree of error, which may vary with each repetition. For instance, the commonly accepted value for Earth’s acceleration due to gravity is 9.80665 \(m/{s^2}\), but if you were to measure it experimentally, you would get a different result. Due to this, it is necessary to have methods to describe errors in measurements. Two important terms that help us evaluate measurement errors are accuracy and precision, and they will be discussed in depth in this article.

Define Accuracy

There always exists a true value of the quantity being measured. For instance, the true value of the refractive index of water is 1.33333. The accuracy of a measurement refers to how close it is to the true value. If a measurement of the refractive index of water gives you the value 1.31, you would consider it to have good accuracy because it is close to the true value. An important thing to note is that accuracy is evaluated on a per-reading basis, and even within a set of readings, each reading may have different accuracy. The overall accuracy of the set can be determined by checking if its mean is close to the true value.

What is Precision?

It is always a good practice to take multiple readings while performing a measurement. This helps minimize errors. For a set of readings to be considered precise, the readings in the set must not deviate too much from each other. For instance, suppose you arrived at the following values while measuring the length of a stick:

1. 1.01 m
2. 1.02 m
3. 0.99 m
4. 1.02 m

As is evident, all of these readings are significantly close to each other, making this a precise set. Contrary to accuracy, precision is defined for the whole set, not just one reading.

 Accuracy and precision

Accuracy and Precision Examples

The following examples will make the concept clearer:

Example 1: Five friends record the height of their 1.76m tall classmate as follows:

1. 1.74 m
2. 1.78 m
3. 1.73 m
4. 1.72 m
5. 1.75 m.

This set is a very precise set since all readings lie close to each other. Within the set, the last measurement is highly accurate since it only deviates 0.01m from the true value. On the other hand, the fourth friend is off by 0.04m and is the least accurate person in the group.

Example 2: This time, let the height measured by the girl’s classmates be:

1. 1.51 m
2. 1.61 m
3. 1.88 m
4. 1.72 m
5. 1.80 m

This set demonstrates low precision since the values are spread so far apart we can’t even decipher what the true value could possibly be.

Distinguish between Accuracy and Precision

What is False Precision? 

False precision can be present in data that appears to be more precise than it actually is. This causes the data to be misleading.

This can occur when converting between units, such as when the speed of a car travelling at 40 mph is expressed as 64.3738 km/h, with four significant digits after the decimal point, despite the original measurement having none. Other instances where false precision may appear include:

1. False precision can arise when unnecessary zeros are added to measurements. For instance, 1 m and 1.00 m are equivalent mathematically, but including the extra zeros in 1.00 m implies a level of precision that may not be achievable by our instrument. This leads to a false sense of precision.

2. Combination of data that carries varying levels of precision can lead to false precision.

False precision

Quantification of Data

The process of expressing a value in numerical terms is known as “quantification”. This is crucial in science as it gives a more defined and specific description of a phenomenon. For instance, calling a burger large has no scientific meaning. Instead, we must specify the weight of the burger for it to make mathematical sense.

Quantification is necessary as computers only understand numerical data, which is a requirement for computer-based analysis. Furthermore, quantification enables us to conduct statistical analysis, which is useful in fields such as machine learning and artificial intelligence.

Practice Questions

Q1. Given that the refractive index of water is 1.3333, discuss whether the following set is accurate and/or precise.

1. 1.32
2. 1.54
3. 1.11
4. 1.61
5. 1.22

Ans. We consider a set like this to be imprecise since the readings vary significantly. At the same time, the value 1.32 is highly accurate, while 1.61 is a very wrong result.

Q2. To measure the length of his pencil, a student uses a metre-scale and writes the result as 0.1237 m. He is given a zero for this measurement. Justify.

Ans. A metre scale does not have the precision the student provided here. It can only measure up to 1 mm, while the student measured it up to one-tenth of a millimetre. This is false precision.

Q3. What makes the following set a bad set of readings for the acceleration due to gravity?

1. 9.805 \(m/{s^2}\)
2. 9.005 \(m/{s^2}\)
3. 10.610 \(m/{s^2}\)
4. 10.100\(m/{s^2}\)
5. 9.512 \(m/{s^2}\)

Ans. If we take the average of these readings, it comes out to be only 0.002% away from the standard or accepted value. One might call that accurate, but these readings vary too much from each other and thus, this set is imprecise.

Summary

Measuring without any form of error is impossible, making it crucial for us to understand and quantify errors in scientific experiments. Accuracy and precision are two key elements in analysing such errors. Accuracy refers to the deviation of a measurement from its true or accepted value and is unique to each individual measurement. Precision, on the other hand, reflects the consistency of measurements within a set, and is not defined for a single measurement. A combination of high accuracy and precision results in reliable data, while a lack of either makes a reading or set of reading bad. False precision occurs when data appears more precise than it actually is, often through presentation or the mixing of data with varying precision. 

Quantification, or converting data into numerical form, is an important process since it is necessary for computer analysis, machine learning, and artificial intelligence.

 

Frequently Asked Questions

1. How do you find the percentage error from a known value?

We can calculate percentage error with the following formula:

\({\bf{e}} = \frac{{{\bf{experimental}}{\rm{ }}{\bf{value}} – {\bf{true}}{\rm{ }}{\bf{value}}}}{{{\bf{true}}{\rm{ }}{\bf{value}}}} \times {\bf{100}}{\rm{ }}\% \)

2. How many significant digits should we use while performing calculations?

In theoretical calculations, we use as many significant digits as are provided to us initially. While performing experiments, the number of our significant digits is determined by the limitations of our instruments.

3. Of accuracy and precision, which is more important?

For scientific data to be considered good, it must be both precise and accurate.

4. Discuss accuracy and precision in terms of statistical analysis.

Statistically, a data set is accurate if its mean is close to the accepted or true value. And for the data to be precise, its standard deviation must be small.

5. How do we decide if our data is accurate enough?

As a general guideline, you can determine the error margin allowed by dividing the place value of the least significant digit by 2. 

For instance, if the true value is stated as 43.71 m, the place value of the least significant digit (1) is 0.01 m. Hence, if your measurement is within ±0.005 m of the true value, it can be considered accurate.

Introduction

Acoustics is a branch of physics that deals with the study of sound, including its generation, transmission, and effects. It encompasses a variety of topics, including mechanical waves in different mediums and the study of various sounds such as vibrations, noises, ultrasounds, and infrasounds. There are various sub-disciplines of acoustics, including aeroacoustics, bioacoustics, and the acoustics of vibration. Acoustics has many technological and scientific applications and is a broad field that extends far beyond just the study of sound.

What is Acoustics?

The field of acoustics involves the study of sounds, their properties and how they interact with the environment. This includes exploring different types of sound waves, such as infrasonic and ultrasonic, and examining their behaviors and effects.

Acoustic Physics

An understanding of mechanical waves is crucial before understanding what acoustics is about. This is because sound itself is a mechanical wave. Broadly, all mechanical waves are classified into two categories:

1. Longitudinal waves
2. Transverse waves

.

Transverse and longitudinal waves

Sound Acoustics

In acoustics, we examine the transfer of energy through sound waves in a medium and how it interacts with its surroundings. Sound is a type of energy that travels as longitudinal waves through compression and rarefaction. Key attributes of sound waves include amplitude, frequency, wavelength, and velocity. The field of sound acoustics delves into the production and propagation of sound waves in a material.

Acoustic energy

The energy used to transmit vibrations from a source to a recipient using acoustic waves is referred to as acoustic energy. This energy was discovered in the sixth century during an experiment studying the characteristics of vibrating strings.

Noise

In our daily lives, we encounter different types of sounds with varying levels of loudness and frequency. The term “noise” refers to a loud, disturbing sound that can be uncomfortable to the ears. Noise can cause discomfort and annoyance to both individuals and their surroundings.

Importance of Acoustics

In our daily life, sound plays an important role and is present in every aspect of our existence. Hearing and producing sound is crucial for our survival and sets humans apart as the most advanced species on Earth with their ability to communicate through speech. Even beyond speaking and hearing, we humans have harnessed the knowledge of sound waves and found various uses for it in industries such as music, architecture, technology, and medicine. Hence, the study of sound, or in other words, acoustics, holds great significance as it has a broad range of applications in multiple domains.

The applications of acoustics

Application of acoustics

Acoustics is an area of science that has numerous practical applications, some of which include:

• Medicine: Ultrasonography and other high-frequency sound-based diagnostic techniques are crucial to our medicinal processes. Sound waves are also used to treat various psychological and physical disorders.
• Controlling noise pollution: Understanding sound sources is crucial in developing methods to reduce negative effects of sound in the form of noise.
• SONAR: SONAR technology uses sound waves to locate underwater objects and determine the sea’s depth.
• Acoustic warfare: SONAR is also being utilised for target identification and location in combat.
• Music: Acoustics play a vital role in producing and synthesising musical instruments, setting up orchestras, and in producing sound tracks, etc.
• Acoustic signal processing: This involves electronic modification of sound and is used in hearing aids, noise-cancelling devices, and other processes like perceptual coding.

Summary

The field of acoustics in physics focuses on the study of mechanical waves, particularly sound waves, and their various applications. It is a constantly evolving discipline and is being researched across multiple areas. Acoustics play a role in almost every aspect of human culture and over time, our understanding of the topic has continued to grow, leading to advancements in the technologies that are available to us. The increasing popularity and applicability of acoustics in various fields is also generating new job opportunities for acousticians and acoustic engineers globally.

Frequently Asked Questions

1. What is acoustics?

Acoustics, as a field of study, encompasses the investigation of sound, from its production to its propagation and eventual effects. It encompasses a range of subfields, including aeroacoustics, environmental acoustics, ultrasonics, and more.

2. What is SONAR?

SONAR is a technique that uses sound waves to locate and communicate with underwater objects. It stands for Sound Navigation and Ranging and is used to determine the position and distance of objects below the surface of the sea.

3. What are mechanical waves?

A mechanical wave is a type of wave that requires a medium to propagate through space, and sound waves are the most commonly known form of mechanical waves.

4. Why are sound waves considered mechanical waves?

Sound waves require a medium to travel through and thus, they are classified as mechanical waves.

Introduction

Acceleration represents the change in velocity of an object. It can either be positive or negative, depending on whether the final velocity is greater or less than the initial velocity. Thus, if the velocity of an object is decreasing with time, it is said to possess negative acceleration or retardation. 

Acceleration is a vector quantity which has both magnitude as well as direction. During circular or rotational motion, the acceleration encountered is referred to as rotational acceleration. Note that it is possible for an object to have zero acceleration if it is moving with a constant velocity.

What is Acceleration? 

In simplest of terms, acceleration is the rate of change of an object’s velocity with respect to time. Hence, its SI unit is given as \(m/{s^2}\).

General Formula of Acceleration

Generally, acceleration can be calculated via the following formula:

Acceleration dimensional Formula in Physics

Acceleration Unit

This is the SI unit of acceleration and other derived units can be found in different systems.

Acceleration Types

Most generally, acceleration can be classified into the following types:

1. Uniform acceleration
2. Non-uniform acceleration

Uniform acceleration: An object whose velocity is changing at a constant rate is said to possess uniform acceleration.

Example: Suppose a car’s speed increases steadily by 30 m/s in 10s throughout a journey. That would mean that the car has a constant acceleration \(3m/{s^2}\).

Non-uniform acceleration: Non-uniform acceleration is acceleration which itself does not remain steady in time.

Example: Suppose that during the first 2 hours of a journey, a car travels with a velocity of 15 km/hr. In the next 3 hours, the velocity changes to 45 km/hr. The change in velocity occurs over unequal intervals of time and thus, over the course of the journey, the car has non-uniform acceleration.

A few other types of acceleration may be stated as follows:

Acceleration due to gravity: This is simply the acceleration experienced by a body due to the gravitational force. Mathematically, it is equal to the gravitational force per unit mass experienced by the object.

Centripetal acceleration: A body in rotational motion experiences this type of acceleration and it is given as the centripetal force per unit mass experienced by a body undergoing circular motion.

Radial acceleration: Acceleration directed along the radius for a body in circular motion is called radial acceleration.

Angular acceleration: Angular acceleration is also experienced by a body in circular motion and its effect is to change the angular velocity of an object.

Coriolis acceleration: Coriolis force comes into the picture when the frame of reference we are considering is itself rotating with a given velocity. The coriolis acceleration is the acceleration encountered due to this coriolis force.

Average acceleration

For a non-uniform motion, we can find out the average acceleration of the object in question to get an overall sense of how it may have moved over the course of its journey. It is defined mathematically as follows.

Instantaneous acceleration

The acceleration experienced by an object at a particular instant in time is referred to as instantaneous acceleration and it is given as the limiting value of the rate of change of velocity of an object when the time interval tends to zero.

Where a= acceleration of the body, s=displacement of the body, and t= time. Thus, instantaneous acceleration is the second derivative of displacement.

Negative acceleration or retardation: Acceleration that slows down the motion of an object is referred to as retardation. For such a phenomenon to occur, the acceleration applied must be negative.

Velocity-Time Graph

Acceleration can also be derived from the velocity-time graph of an object. The slope of the graph gives us acceleration as a function of time and if we find the value of this slope at a particular point, i.e., the slope of tangent at a point, we arrive at instantaneous acceleration. 

Graph for average acceleration

Graph for instantaneous acceleration

Graph for uniform acceleration

Graph for non-uniform acceleration

Examples of Acceleration

Example 1: A body moving with \(20m/{s^2}\) comes to a halt after 5.2 secs. Find the nature of acceleration and its value.

Solution: 

Example 2: If a car is moving with a velocity of 45 m/s and after 10 s, its velocity becomes constant at 60 m/s, find acceleration.

Solution:

Difference between Acceleration and Velocity

Summary

Acceleration measures the change in velocity of an object. Its SI unit is \(m/{s^2}\) and it is a vector quantity with both magnitude and direction. It can be determined as the first-order derivative of velocity or the second-order derivative of position vector.  An object moving with a constant velocity has zero acceleration since the derivative of a constant is equal to zero. 

Frequently Asked Questions

1. Give two examples of retardation.

Two examples of retardation are as follows:

1. A train that reaches a halt will slow down and thus, experience retardation.
2. A ball thrown upwards experiences retardation due to gravity.

2. What is the SI and CGS unit of acceleration?

In SI units, acceleration is measured in \(m/{s^2}\)  and in CGS units, in \(cm/{s^2}\).

3. What is gravitational acceleration?

Gravity is the force by which the Earth attracts a body towards its center. This force generates acceleration in a vertical motion, known as gravitational acceleration. The motion of an object falling solely under the effect of gravity is termed as free-fall.

4. What is the value of gravitational acceleration?

The approximate value of acceleration due to gravity is \(9.8m/{s^2}\).

5. What is angular acceleration?

Angular acceleration measures the time rate of change of angular velocity of an object and thus, is measured in \(rad/{s^2}\).

6. What is a Coriolis force?

Coriolis force is experienced by objects which are moving in a frame of reference that is itself rotating with a given angular velocity. It is responsible for wind in certain regions of the Earth.

Introduction

An atom is the smallest component of any given element. Subatomic particles like as the proton, neutron, and electron can be further isolated from atoms, which were once thought to be invincible. Since the quantity of protons and electrons in every atom is the same, every atom is non-conducting.

When an atom loses or gains an electron, the resulting change in charge is noticeable. These charged particles are called ions. Either by gaining electrons (in which case they are called anions) or by losing them (in which case they are called cations), atoms and molecules acquire or lose their charge. The atomic theory’s central idea is that atoms are the smallest building blocks of matter. None of the simplest chemical compounds or elements are capable of decomposing any further.

Atom

A nucleus, which is positively charged, is packed closely with electrons, which are negatively charged, to form the smallest unit of an element called atom. The structure of an atom, on the one hand, and the additional nucleus region, on the other. The neutron (n°) and the proton (P+) make up the atomic structure. Negatively charged electrons are housed in the supplementary nucleus (e-).

All elements and compounds, including atoms, have mass. The protons in an atom’s nucleus are largely responsible for the extreme density of matter there. The proton is the most massive subatomic particle, followed by the neutron and then the electron.

An electron orbits the nucleus of a hydrogen atom, which contains a single proton. Hydrogen is the most lightweight element.

The nucleus of each atom has a specific amount of protons, and these protons attract a matching number of electrons, rendering the atom electrically neutral. Ions can be created by either adding or removing electrons from atoms. A few examples of these elements are hydrogen, nitrogen, oxygen, and iron.

Features of atom on the bases of modern atomic theory 

1. The term “modern atomic theory” is used to describe the most up-to-date, canonical explanation of atoms.
2. According to the foundations of atomic theory, atoms are the smallest units of chemical matter. They are the most basic building blocks of chemistry; they cannot be broken down any more.
3. Each element has its own distinct atomic structure, which differs from that of every other element.
4. Although, atoms can break down into much smaller particles. The nucleus of every element contains the same amount of protons, which are positively charged subatomic particles.
5. Neutrons are also present in the nucleus, albeit the exact number varies amongst isotopes of the same atomic type.
6. There are two types of atoms in the universe: isotopes, which have a varied number of neutrons but the same number of protons. For example, whereas all hydrogen atoms share a single proton, hydrogen-2 also has a neutron while hydrogen-1 does not.

Ions 

When the number of protons and electrons in an atom becomes unbalanced, ions form. Common charged particles include ions. An ion could have either a positive or a negative charge. If an atom has an electrical charge, it is said to be an ion. An anion is an atom in which the number of electrons is greater than the number of protons. When there are more protons than electrons in an atom, we call it a cation. It’s doable without any outside help. In the process of gaining or losing electrons, an atom becomes an ion. Ions can be divided into two categories: anions (-) and cations (+).

When an atom receives an electron, its electron count rises; as a result, it acquires a negative charge. When an atom loses an electron, it receives more protons than it loses, giving the atom a positive charge.

Difference between Atom and Ion

Summary

The contemporary atomic theory suggests that there are two components to an atom. The nucleus and the atomic orbitals. Electrostatic repulsion does not exist between protons and neutrons, hence the nucleus is composed of both types of particles. All stuff is composed of smaller and smaller particles called atoms. Subatomic particles can change into ions by gaining or losing an electron. Ions are sometimes mistaken for atoms, but not always; some compounds can undergo an electron-loss or -gain transformation to become ions. Ions have a net electrical charge, while atoms do not; this is the main contrast between the two.

Frequently Asked Questions

1. What is the function of the nucleus in an atom?

Ans. The nucleus of an atom contains the vast majority of the atom’s mass in the form of protons and neutrons. These two hold down the nucleus. The electrons orbit the nucleus.

2. Does the property on an ion differ from its parent atom?

Ans. Ions have different electronic configuration than their parent atoms. It results in different chemical properties because of the presence of charge. It also differs in terms of size. 

3. Who discovered atom?

Ans. Democritus invented the atom in 450 B.C. He separated a matter into smaller and smaller fragments until it could no longer be divided. He called them atomos, afterwards renamed atoms. John Dalton revives Democritus’ hypothesis and performs several experiments to establish atoms exist.

Introduction

The term “fluid” is used to describe a material that may take on several forms. Things that are fluids are ones that can be moved around rather easily. This chapter focuses on the physical properties of viscosity and surface tension shown by fluids. The two processes are dependent on molecular interactions. Both surface tension and viscosity are measures of a fluid’s elasticity; the former is responsible for the fluid’s relatively small surface area, while the latter indicates how much is its fluidity. 

What is Surface Tension?

• Surface tension is a fluid’s tendency to take on the smallest possible footprint on a surface.
• Liquids have this quality because the molecules near the surface are in a different state from the molecules deeper in the substance.
• When a molecule sinks below the liquid’s surface, it is surrounded by other molecules and experiences equal attraction in all directions.
• Therefore, the molecule is not being attracted by any net force.
• Surface tension is affected by the attractive forces exerted by the surrounding solid, liquid, and nearby particles, as well as those exerted by the particles themselves.
• As the temperature is increased, the surface tension and the net force of attraction between molecules are both diminished.
• The energy needed to increase the liquid’s surface area by one unit is released by surface tension. The fundamental characteristic of the liquid surface that resists force is also surface tension. In particular, it maintains a barrier between the liquid and foreign objects, and it also acts as the force holding the molecules of liquid together.

Applications

• Surface tension is a major factor in many manufacturing processes.
• All businesses with a research and development department use surface tension phenomena to better their products.
• Among the various methods used to raise the standard of production is the development of new detergent formulas.
• Detergent formulations that incorporate more biological surfactants allow for more effective cleaning at lower temperatures.
• Characterizing food, medicine, and packaging all rely heavily on surface tension data.
• Raindrops are spherical because of the cohesive connections between the precipitation molecules and the surface tension of the water molecules.
• Detergents are helpful due to their property of su
• Adding soap or detergent to water lowers the surface tension of the liquid, allowing the water molecules to permeate the fibres and wash away the oil and liquid wax.
• Oil’s lower surface tension than water makes it easier for it to spread across the water’s surface.
• Mosquito eggs can float on the water’s surface because of the water’s surface tension.
• Soap is often included in toothpaste formulations because it reduces the product’s surface tension, allowing for easier distribution.

What is Viscosity?

• Viscosity is a measure of resistance to a fluid’s capacity to flow. 
• The resistance to the movement of a fluid, or its viscosity, is the result of friction between the molecules in that fluid.
• Fast-moving fluids have less internal resistance than slow-moving fluids. This is because of the intense intermolecular forces at play.
• Those liquids that move very slowly have a high internal resistance. The cause of this is the weak intermolecular forces present between them.
• An rise in temperature reduces the viscosity of liquids but raises that of gases. Therefore, heat makes liquids more pliable, whereas gases become more resistant to change in velocity.
• When a liquid’s viscosity increases, its flow rate decreases.

Applications

• The highly viscous fluid is used as brake oil in hydraulic brakes and to dampen the movement of a variety of instruments.
• The way blood flows through arteries and veins is regulated by the viscosity of fluids.
• When it comes to lubricating the moving elements of heavy equipment, oil with a high viscosity coefficient is your best bet. Insight into the viscosity of a lubricant and how it changes with temperature can help us select the most appropriate option.
• To find out how much an electron weighs, Millikan used the oil-drop experiment. Because of his expertise in viscosity, he was able to calculate the potential energy.

Summary

The viscosity of a fluid is directly proportional to the amount of friction it encounters as it moves through a given space. The resistance to motion in a fluid, known as its viscosity, is caused by friction between the molecules of that fluid. Internal resistance is lower for fluids that are moving quickly. This is because of the intense intermolecular forces at play. The tendency of a fluid to leave as small a footprint as possible on a surface is an example of surface tension. Liquids have this property because molecules at the surface are in a different state from those deeper in the material. 

Frequently Asked Questions

1. What is the difference between dynamic and kinematic viscosity?

Ans: The friction between two layers of a fluid during motion is known as its dynamic viscosity. As most cases, it will be expressed in centipoise. The dynamic viscosity of a fluid is converted into a kinematic viscosity by dividing it by the fluid’s density.

2. How is viscosity measured?

Ans: The viscosity is determined using the viscosity coefficient. This value is independent of the specific liquid being analyzed and remains constant over time. Formally, the coefficient of viscosity is estimated using the Poiseuille’s method, in which the liquid flows through a tube at various pressures.

3. What benefits does viscosity in vehicle industry?

Ans: Increases in viscosity, brought on by higher temperatures, tend to lessen wear and oil consumption. A decrease in viscosity caused by cooler temperatures improves ignition and reduces fuel use.

Introduction

Evaporation is the transition from the liquid to the vapour phase that takes place at pressures and temperatures below the boiling point (a condition of a substance just below its critical temperature). Evaporation occurs only when a substance’s relative vapour pressure is less than its equilibrium state vapour pressure. However, rather than a phase shift from liquid to gaseous, boiling is the formation of vapour as vapour bubbles immediately below the surface of the liquid. Rather than the literal conversion of the substance to gas, the term “vaporisation” has been used informally or hyperbolically to represent the actual physical disintegration of an object when subjected to high temperature or explosive force.

What is Vaporization?

Vaporization can be thought of as the transformation from a liquid to a gaseous state. When the temperature is raised, the kinetic potential of the molecules also increases. The force of attraction between molecules weakens as their kinetic energy increases. Because of this, they become airborne and spread over the area. This process requires the use of thermal energy.

Types of Vaporization

There are three types of vaporisation:

Evaporation

If you lower the temperature of a liquid below its critical point, you can cause a phase transition is known as evaporation to occur, in which the liquid changes into a gas.

The top is the primary site of evaporation. To begin evaporating, a substance must have a partial vapour pressure less than its equilibrium. So, for instance, if you continuously sucked the air out of a solution, you’d eventually be left with just a cryogenic liquid.

Boiling

Boiling is not a phase transition from the liquid state to the gaseous state but rather the creation of vapour below the surface of the liquid as vapour bubbles. Boiling occurs when the chemical’s equilibrium vapour pressure is higher than or equal to the ambient pressure. The boiling point of a substance is the temperature at which boiling occurs. The boiling point is affected by atmospheric pressure.

Sublimation

We know that ice melts into a liquid, and subsequently, the liquid evaporates into steam. However, there is a process through which matter can transition from its solid state into its vapour state, bypassing the liquid state entirely. Sublimation is the direct transformation of a solid into a gas.

Factors affecting the Rate of Vaporization

The rate of vaporization is affected by several factors, such as:

• The concentration of minerals in the solution.
• The amount of a substance that evaporates into the air.
• Due to the increased interactions between the molecules, more energy is needed to escape the liquid state.
• The point at which the liquid or gas begins to evaporate is called the vaporisation temperature. 
• Reduced surface tension allows molecules to escape the surface faster, leading to increased evaporation rates.
• Evaporation rate is proportional to the surface kinetic potential of the molecules, which increases with temperature.
• Width of the Surface: Evaporation rates are proportional to the number of particles on the surface, so a bigger surface area means higher evaporation.
• If “clean” air (wind that is not yet laden with a drug or even other chemicals) is constantly passing across the substance, allowing for rapid evaporation, the amount of the chemical in the atmosphere is less likely to rise over time.
• Humidity refers to the amount of water vapour in the air.
• Because warmer air can hold more water vapour than cooler air, the evaporation rate will increase if the wind speed and humidity stay constant.

Examples of Vaporization in Our Daily Life 

• Clothing that has been soaking wet can be dried through evaporation.
• This occurs when moisture in damp garments is evaporated when exposed to the sun’s thermal radiation.
• Separating the components of a mixture using this method is a common practice in many industrial processes.
• Using a vaporisation process, salt is produced from seawater in an industrial setting.
• Evaporation is used to remove salt from saltwater to produce table salt.

 

Frequently Asked Questions

1. What is the significance of the latent heat of vaporisation?

Ans: During a change of condition, heat energy is effectively hidden.

Latent heat, a form of hidden power used only during phase transitions, is also called the latent heat of vaporisation when it happens during the phase transition from liquid to gas.

2. What is critical temperature?

Ans. It is possible to define the critical temperature of a substance as the greatest temperature at which the substance can be in a liquid state.

No amount of pressure can cause a gas to turn into a liquid after it has reached a temperature over its critical temperature.

3. Does latent heat of vaporisation depend on the mass of the substance?

Ans. No, the latent heat of vaporisation does not depend on the mass of the substance. It has a fixed value at a given temperature and is not affected by the substance’s mass or volume.