Category: Chemistry

Introduction

The whole universe is composed of two parts; system and surroundings. There occurs an exchange of heat between the system and the surroundings. Thermodynamics tells us about the exchange of heat, different forms of energy, and the transformation of energy into work. It also explains some other properties of the system like temperature, pressure, density, enthalpy, entropy, etc.

Define Thermodynamics

Thermodynamics is a topic that derives the relationship between heat, energy, work, and temperature. According to thermodynamics, if the system does the work then its value will be negative and when work is done on the system its value will be positive.

Difference between Thermodynamics and Statistical Mechanics

Define System and Surroundings

System: The part of the universe in which all the matter remains is known as a system. 

Surroundings: The other part of the universe outside the system is known as the surroundings. The system and surroundings are divided by a boundary.

Classification of the system:

1. Open system: It has the capacity to exchange both energy and matter with the surroundings. In an open system, both the temperature T and pressure P are constant. For example, the human body.
2. Closed system: This system only exchanges energy with the surroundings. The entropy of a closed system is always constant. For example, water boils using a closed lid.
3. Isolated system: It exchanges neither matter nor energy with the surroundings. For example, a thermos flask is an example of an isolated system. 

Different types of processes in thermodynamics

• Isothermal process: In this process, the temperature (T) of the system is always constant.

1. Isochoric process: Here, the volume (V) of the system is always constant.
2. Isobaric process: In this process, the pressure (P) of the system remains constant.
3. Adiabatic process: In this process, the change in heat (Q) with the surroundings is zero.

Properties of thermodynamics

1. Intensive properties: These properties don’t change with the change in the amount of matter. For example boiling point, melting point, density, etc.
2. Extensive properties: These properties highly depend on the amount of matter in the system. For example mass, volume, etc.

Functions in thermodynamics

1. State functions: These functions change with the change in the state of a system. For example Enthalpy (H), internal energy (U), entropy(S), and density (d). 
2. Path functions: Heat (Q) and work (W) don’t depend on the state of a system, but rather depend on the path of a system. They are called path functions.

Define Enthalpy and Entropy

Enthalpy (H): It is a property of thermodynamics that indicates the overall heat capacity of a system. It is expressed by the sum of the system’s internal energy and the product of the pressure and volume of the system. 

H = U + PV

Depending on the symbol before the value of enthalpy, any reaction can be classified into two parts.

• Exothermic reaction: The reaction is called exothermic when heat is generated during a reaction. The value of enthalpy in an exothermic reaction is always negative.
• Endothermic reaction: When the system absorbs energy from the surroundings to execute a reaction is called an endothermic reaction.  The value of enthalpy in an exothermic reaction is always positive.

Entropy (S): It measures the extent of disorderness of a system. For a spontaneous reaction, entropy S is always negative and for a non-spontaneous reaction, entropy S is always positive.

Thermodynamic potential

Thermodynamic potentials are used to define a particular state of the system. They are internal energy (U), enthalpy (H), Gibbs free energy (G), and Helmholtz free energy (F).

Laws of thermodynamics

• Zeroth law: This law states: “if two bodies A and B are each in thermal equilibrium with some third body C, then they are also in equilibrium with each other.”
• First law: This law states:  “Energy can neither be destroyed nor be created, it can only be transferred from one form to another”. It is also called the “Law of conservation of energy.”

ΔQ = ΔU + W

ΔQ= Change in heat of a system.

ΔU = Change in internal energy of a system.

W = Work done

• Second law: This law states: “any spontaneously occurring process will always lead to an escalation in the entropy (S) of the universe.”

\[\Delta {S_{Total}} = {\rm{ }}\Delta {S_{system}} + {\rm{ }}\Delta {S_{surroundings}} > {\rm{ }}0\]

• Third law: This law states: “the entropy of a system approaches a constant value as the temperature approaches absolute zero.”

\[{S_{T = 0}} = 0\]

Daily life examples of thermodynamics

1. Human bodies sweat, producing heat from the body.
2. Melting of ice cubes.
3. Like A thermodynamic system, the human body exchanges mass and energy with the surroundings.

Summary

A type of heat energy that connects with other types of energy is called thermodynamics. Heat or work are two ways that energy is changed or exchanged. In thermodynamics, there are four processes. They are isothermal, adiabatic, isobaric, and isochoric. Thermodynamics explains many important properties of the system. Energy is the dominant focus of thermodynamics which is how it is used and transforms from one state to another. Thermodynamics frequently includes using heat to generate work like in the engines of automobiles and generating work to transfer heat like in the refrigerator.

Frequently Asked Questions 

1. Why does thermodynamics emphasize energy?

Ans: The first law of thermodynamics defines that the total energy of the system is always conserved. Neither energy can be created nor destroyed. It is only capable to change from one type to another. Like, in the combustion of fuel the chemical energy is transformed into thermal energy.

2. Why is it referred to as free energy?

Ans: Because it is readily accessible at all times, Gibb’s free energy is known as free energy. If necessary, the reaction can obtain this energy without exerting any effort.  Enthalpy (H) and also the product of the system’s temperature (T) and entropy(S) are added to determine the change in Gibbs free energy (G).

G = H +TS

3. What are the drawbacks of thermodynamics?

Ans: Thermodynamics can’t explain any properties of the system quantitatively. It doesn’t include the direction of the flow of heat. It can’t tell anything about the spontaneity of any reaction. These are the drawbacks of thermodynamics.

Introduction

The shortest form of polymers is called monomers. Depending on their characteristics, preparation process, and many other factors, they are classified into two types- Natural and Synthetic polymers. The polymers which are generated naturally are called natural polymers, whereas polymers made by humans in some synthetic processes are called Synthetic polymers. There are different kinds of useful synthetic polymers. Thermosetting polymers are one kind of them.

Define Thermosetting Polymer

A thermosetting polymer can be called by another name ‘Thermoset’. By heating the thermosetting polymer, it undergoes irreversible changes. It has a cross-linking structure, forming a three-dimensional network. Initially, these polymers remain in a liquid state and they are soft. But after heating, they become harder. The rate of cross-linking in them increases with an increase in temperature, pressure, and amount of catalysts. Bakelite, Duroplast, and Melamine resin are examples of thermosetting polymers. 

Features of thermosetting polymers

This type of polymer has unique properties unlike the other types of polymers. 

1. Monomers are condensed easily and form polymers. Thermosetting polymers are types of condensation polymers.
2. Due to the high cross-linking process, the molecular weights of these are very high.
3. Thermosetting polymers possess exceptionally high melting points and very strong tensile strength.
4. It is not reprocessed to its original state because of the intense cross-linking. It is created permanently. In other words, the reaction mechanism is irreversible.

Synthetic pathway of Thermosetting Polymer

The initial stage of thermosets is a resoluble, molten, and insoluble state. Next, it transforms into a thermoplastic-like substance that is slightly soluble and has certain reversible properties. Following this phase, polymers undergo cross-linking and hardening. Finally, a 3D network containing polymers is formed. There is also another method of preparation containing three steps.

1. Moulding by compression: Here a heated mould cavity is used and then it is compressed to produce the plastic. With an increase in the application of heat on mould, the chemical interaction also increases.
2. Transfer moulding: The utilization of a transfer pot is common in this kind of manufacturing, and heating the mould within it, will enhance the materials’ flow.
3. Injecting the mould: Screws are employed in the injection moulding process to inject the high volume of polymer into the appropriate moulds. Additionally, it is discovered that the liquification of these polymers decreases the polymers’ viscosity.

Advantages of Thermosetting Polymers 

1. For thermosets, both chemical and heat resistance are excellent. It’s employed for packed items and has a strong deformation resistance.
2. Thermosets are beneficial for wet paste formulations since they contain minimal solvent.
3. The linked chains cannot freely travel because the use of heat turns them hard.
4. Epoxy and phenolic resins have a wide range of uses, particularly in the production of circuit boards and containers.

Disadvantages

1. It cannot be converted to its original state after it has formed.
2. With thermosets, fine surface quality is not achievable.
3. This polymer should be managed with utmost care.

Summary

Bulk molecules, known as polymers, have numerous industrial uses. There are two categories of polymers, both natural and artificial. Artificial synthetic polymers are generated by executing specific chemical changes. Because they’re irreversible polymers, even after heating, they cannot be reverted to their initial position. Therefore, it is an extremely rigid and hard polymer. During the curation process of thermosets, chemical interaction occurs in them. So remoulding is not possible. But for thermoplastic polymers, no chemical interaction occurs during curation. Due to the possibility of remoulding in thermoplastic polymers, thermosets are a better option than thermoplastic polymers.

 

Frequently Asked Questions

1. What are the reasons that thermosets don’t melt?

Ans: During the curation process, cross-linking occurs in the polymers to produce an unbreakable and permanent bonding. It is clear that even with the application of strong heat, thermosets can’t be melted.

2. What are the reasons behind the ignition of thermosets?

Ans: Thermosets possess significant melting points, but as soon as they reach a particular temperature and harden, their parts and physical features become fixed. They cannot be transformed back into their original shapes or sold for scrap again. Rather the substance will just burn or char.

3. Do thermosets participate in the crystallization process?

Ans: It is found that thermosets are amorphous in nature. Due to the high cross-linking process in their structures, they don’t crystallize.

Introduction

Thermoplastics, polystyrene, and polyethylene can both be regularly moulded. It is therefore feasible to heat a foamed polystyrene cup while also moulding it into an irregular shape. For example, a dish. Individual molecules are separated from each other and move through one another in the polymeric material associated with thermoplastics. But even though the molecule may be straight or diverging, with molecular weights ranging from incredibly low to exceptionally high. Thermoplastic polyurethane (TPU) has a chemical formula \({C_{27}}{H_{36}}{O_{10}}\).

Define Thermoplastic Polymers 

1. Additional polymerization leads to the production of thermoplastics, which are softer and less brittle. Organic solvents can dissolve them.
2. Thermoplastics can also be heated to a soft state and then moulded into another structure while they remain warm.
3. They lose their ability to retain their carved shapes as they cool because they solidify. They can be warmed frequently and moulded into another form without altering their chemical components.
4. The thermoplastic polymer group is generally categorized as either amorphous or crystalline. The creation of thermoplastics involves combining subunits, which are small molecules.
5. A simple polymer chain can be produced using thousands of monomers. 
6. A simple polymer chain can be produced using thousands of monomers.
7. Though mild forces exist between sequences in polymers, the atoms are held together by powerful covalent bonds.

Features of Thermoplastic Polymers

1. They are polymers with very high molar mass.
2. With an increase in the temperature, intermolecular interaction in the cross-linking becomes weak. So a viscous liquid is produced.
3. There is the availability of thermoplastics which can be recycled easily.
4. They can behave as flame retardants.

Different types of Thermoplastics

1. Polystyrene: A polymer composed of repeating units, styrene is termed polystyrene. It is also known as poly-phenylethene. It’s actually a thermoplastic polymer, which indicates that when warmed, it weakens and melts and may be reprocessed. It resists substances like acids and bases and makes a great electrical insulator.
2. Polyvinyl chloride: PVC is properly known as Poly Vinyl Chloride. The polymerization of Vinyl Chloride creates PVC, a polymer. Several products, such as wires, raincoats, bottles, credit cards, etc. include PVC. It can be utilized to make a wide range of goods because it is fire and water-resistant.
3. Polypropylene: Polymerized propylene is used to create the synthetic polymer known as polypropylene. Polypropylene is moulded or produced into a wide variety of plastic goods wherein hardness, elasticity, lightweight, and temperature resistance are necessary.
4. Polyethylene: The most prevalent form of consumer plastic is polyethylene, which is also found in numerous everyday items. It’s a thermoplastic substance, which means that it can be repeatedly heated to a liquid state and then cooled to a solid state.

Influence of additives on the thermoplastics

1. Contrary to unprotected polypropylene, it has poor resistance to UV light. Additives like limited amines reduce the light and enhance the lifespan of the material.
2. Flame retardants, glass fibers, minerals, conductive fillers, colors, lubricants, and a range of many other polymer additives can be employed to enhance the mechanical and physical properties of polypropylene.

Application of Thermosets

1. Thermoplastic is an ingredient in producing sporting goods. Toys can also be made with it.
2. It is utilized in making the components of automobiles.
3. The thermoplastic polymer is employed to manufacture containers including shampoo bottles, drinking bottles, and food storage bins.

Advantages of Thermosets

1. It is a procedure that requires little energy.
2.  It gives a wide range of good quality products.
3. It produces very high-volume and precise manufacturing that is less expensive.
4. Metals can be substituted by a variety of substances with significant weight-saving benefits.

Disadvantages of Thermoplastics 

The following drawbacks of thermoplastics may influence the choice of material:

1. When exposed to UV rays or intense sunshine, thermoplastics deteriorate more quickly.
2. Not every thermoplastic is resistant to polar solvents, organic solvents, or hydrocarbons.
3. Some varieties exhibit creep when subjected to prolonged loading.
4. Under severe load, breakage occurs instead of deformation.

Types of polypropylene

The two primary forms of polypropylene are copolymers and homo polymers. Block copolymers, as well as random copolymers, are two more categories of copolymers. Different applications match every class more effectively than others.

Summary

Thermoplastics are simple to reuse because they solidify after cooling and exhibit no changes in chemical properties after being warmed and cooled numerous times. The repeating unit like urethane moiety is used to make thermoplastic polyurethane. This thermoplastic is usually produced through the interaction of a di-isocyanate and a polyol (organic compound). TPU has low TM between 87 to 90 °C and low Tg at 25 °C.

 

Frequently Asked Questions

1. Why can thermoplastics be recycled?

Ans: The intermolecular interactions in thermoplastic polymers are weak despite their strength. They have great recyclability.  Plastics can become less reusable as they go through the recycling process due to a variety of applications.

2. Why is PAI the strongest thermoplastic?

Ans: At 21,000 psi, PAI – Polyamide Imide (PAI) has the greatest tensile strength of almost any plastic. The maximum tensile strength of every unreinforced thermoplastic, radiation tolerance, intrinsic low combustibility, smoke production, and good thermal stability are all characteristics of this efficient plastic.

3. Do thermoplastics have an acidic nature?

Ans: Based on a variety of factors, any item may be technically or inherently hazardous or safe. TPU is harmless for many purposes and isn’t necessarily hazardous. It is employed in the biomedical field as well. A variety of factors may lead to polymers’ toxic effects.

Introduction

In the modern periodic table, the elements are organized according to their atomic numbers. There are 7 rows and 18 columns in the periodic table. Noble gases belong to group 18 in the periodic table. The gases are helium, neon, argon, krypton, xenon, and radon. They remain in a gaseous state at normal pressure and temperature. To maintain inert conditions these noble gases have a great role. 

Define Noble Gas 

The noble gases have their valence shell completely occupied. Helium, neon, argon, krypton, xenon, and radon are known as “noble gas”. Due to their inertness, they react with very few elements. Even upon the addition of strong acids or bases, it remains unreacted. For this reason, they are named so. 

Physical characteristics of noble gases

• Atomic size: On moving down the group, one more shell gets added up. That is why nuclear attraction towards the valence electrons decreases. So, atomic size goes on increasing. 
• Melting point and boiling point: Due to very poor interatomic interaction, the melting point and boiling point of noble gases are very low as compared to other elements in the periodic table. Among them, helium has the lowest boiling point of -268.9 ℃. At room temperature, all these elements are in gaseous form. 

• Density: Usually the density of these noble gases is very low. But on descending the group, density increases as mass increases. Radon has the highest density among them. 
• Solubility: Noble gases dissolve in water at a very low extent. The dipole-dipole interaction is the main reason for their solubility in water. On moving down the group solubility increases. 

Chemical properties of noble gases

• The valence shells of noble gases are completely occupied. So, they are inert.
• Noble gases are very stable and always stay in the ground state energy level.  
• Only krypton, radon, and xenon can react chemically with high electronegative elements. 
• Noble gases are inflammable. 
• They have a very good electricity-conducting nature so they are also used as fluorescence material.  

Application of Noble gases

Helium

• Due to its low density, helium is utilized to fill airships and colorful balloons.
• At -269℃, helium can boil. Due to its low boiling point, it functions as a very effective coolant. Electrical resistance is lost.
• Sea divers carry tanks with a mixture of helium and oxygen in them. The divers can breathe in a nitrogen-free environment as a result, and deep diving nitrogen narcosis is prevented.
• Superconducting wires are used in the coil of MRI machines to carry huge electric currents. Strong magnetic fields could form as a result of the electric currents. Helium assists in lowering the conducting coils’ temperature to the point where superconducting qualities may be seen.

Neon

• Neon used in vacuum discharge tubes receives electrical energy and glows as a result neon is utilized in displays.
• Lasers are made from neon and helium.

Argon 

• For both incandescent and fluorescent bulbs, it is a crucial element. Because it won’t react with a tungsten coil, it is utilized in incandescent light bulbs instead of air.
• It provides an inert insulating condition for titanium fabrication where arc welding is used. 
• It is used to create the conditions devoid of oxygen required to grow semiconductor crystals.

Krypton 

• This gas has a very useful role in advertising signboards because it shines brightly when electricity is passed through krypton vapor inside a vacuum discharge tube.
• Krypton lasers are used during surgery to cure some eye conditions and to remove birthmarks.
• High-speed photography frequently uses argon and krypton to create photo flashes.

Xenon 

• Bacteria-contaminated surfaces can be eliminated by the illumination produced by xenon lamps.
• It produces a bright white light that flashes, making it ideal for creating strobe lights.
• To increase the clarity in CT scan imaging, oxygen and xenon are combined.

Radon

• When it is dissolved in water, it can treat inflammatory disorders such as arthritis.
• Radon’s inherent radioactivity promotes cancer treatment. Direct placement of radon glass vials is one method of performing targeted radiation therapy.

Summary 

The periodic table’s right-hand end column is where noble gases can be found. Helium, neon, argon, krypton, xenon, and radon are all non-metals and can also be referred to as inert or “noble gases”. The sizes of atoms of these gases increase as one descends from helium to radon.  The density, melting, and boiling temperatures of the noble gases are extremely low, and they are insoluble in water. Noble gases are all odorless, colorless, and poor heat conductors. They have a very low reactivity to chemicals and are combustible.

Frequently Asked Questions

1. What distinguishes radon from other noble gases?

Ans. The heaviest noble gas, radon (Rn), is radioactive and occurs naturally as a byproduct of the disintegration of radium, thorium, and uranium. As a result, radon is unique among noble gases.

2. What occurs when an electric current travels through noble gases?

Ans: Because of their chemical inertness, noble gases are employed in displays. When an electric current is applied inside a vacuum discharge tube, they emit a dazzling glow.

3. What are the common characteristics of periodic groups?

Ans: A set of periodic tables’ elements share similar chemical characteristics that result from the existence of many electrons. It takes into account the number of valence electrons an atom has in its outer shell.

Introduction

Water is considered to be the most important material in the daily life of humans. Not only humans but animals and plants also depend on water for survival. Its molecular formula is \({H_2}O\) where two H atoms are covalently bonded with the O atom. The ratio of the number of H and O atoms is 2:1. A major part of the human body is filled up with water. Water is a polar and colorless substance. Due to the polarity of water, any polar substance becomes soluble in water. Looking after the contribution of water on earth, scientists are doing much research on this.

Polarity in water

Water can be written by its chemical formula \({H_2}O\). It is composed of two H and one O atom. The electronegativity of O is much higher than H atoms. As a result, A negative charge is generated on the O atom and H atoms become positively charged. Due to this charge separation, water becomes a polar compound.

Water as ‘Universal Solvent’

Water is a polar liquid. Most of the salts contain both positive and negative charges in their structure. As a result, they are polar in nature. water is also a polar liquid. That is why the salts become soluble in water. Not only salt but many other compounds can also easily be dissolved in water. Due to the universal use of water as a solvent, it is called a ‘Universal Solvent’.

Features of water

1. Water has very high surface tension and high specific heat.
2. It easily contains heat.
3. The conducting power of electricity in water is very low. This conductivity increases when the number of ionic substances in water increases.
4. Water is a colorless, tasteless and odorless liquid.

Involvement of water in chemical reactions

1. Redox reaction: Water behaves as both oxidizing and reducing agent. In the reaction of water with any metal, water is reduced to hydrogen. Hence it can behave as an oxidizing agent. Again when any electronegative element reacts with water, water is oxidized to oxygen. Then water becomes a reducing agent.

1. Reaction with acid and base: Water can react with both the acid and the base. That’s why it is called ‘amphoteric’. The pH of water is always 7 i.e. it is neutral in nature. It can accept protons from acids like H2S and can donate protons to bases like NH3.

1. Self-ionization of water: Small extent of self-ionization occurs in water. Water ionizes to for

Importance of water in our lives 

1. Maintain cellular structure: Water can get into various cells and produce pressure so that air can’t be filled in it like a balloon. so the actual cell structure is maintained. Water always helps to maintain the proper molecular form of the cells in plants.
2. Daily activities: In our daily life, water helps in various activities like cleaning, washing, bathing, cooking, etc.
3. Farming: Farming is totally based on water. With the changes in the amount of rainwater, the growth of crops is hampered a lot.
4. Control the pH of the body: Water controls the temperature of our body as well as the pH of our body.
5. Enhancing body function: consumption of enough water can enhance the function of the brain. It helps in the easy digestion of foods. Water acts as a lubricant and fills the joints of our body with fluids. It can lower the risk of a massive heart attack in the human body. 

Summary

Water is the most vital fluid on the earth. Without water, the survival of humans, animals, and plants will be uncertain. The chemical formula of water is \({H_2}O\). Water is polar in nature. So it can dissolve most of the salts in it. Not only salt, but numerous compounds also become soluble in water. That’s why water is called a “Universal Solvent”. Water can enhance many functions of the human body. About 75 % of the human body is composed of water. Water is amphoteric in nature. For this reason, it is involved in many chemical reactions. Water is also essential for many industrial purposes.  It is also used in several activities of our daily life. Every form of life on the earth will be deeply affected without water.

Frequently Asked Questions

1. How will life be without water?

Ans: Rapid dehydration will result in intense thirst, exhaustion, and, eventually, organ malfunction and death. On the first day without water, one can feel mildly lethargic and thirsty, but by the following day, they might be in organ dysfunction. Everyone is not affected by dehydration in the same manner.

2. What are the consequences if we don’t safeguard our water supplies?

Ans: If water is not conserved, a suitable water source may be lost, which could have catastrophic consequences. This included higher costs, less food supply, health hazards, and civil turmoil. It promotes the survival of our ecology.

3. Why is it so crucial to save water?

Ans: Fuel can be saved by conserving water. Reducing daily water intake also lowers your overall carbon footprint because it requires energy to heat, purify, and draw water into our homes. Utilizing less water not only helps save water but also to protect wetland habitats that are home to fish, herons, water small animals, otters, and other species.

Introduction

In the periodic table, all elements are ordered by following their atomic numbers and periodic characteristics. Antoine Lavoisier tried to classify elements as metals or non-metals in 1789. Johann Wolfgang Dobereiner, a German physicist, attempted to assemble atoms in atomic mass-increasing triads later, around 1817, but this method was unsuccessful for all elements. The elements were later connected depending on the atomic masses by scientist John Newland, who was also unsuccessful. After numerous experts, Dimitri Mendeleev, a Russian chemist, begins to classify elements according to their atomic weights and other physical and chemical characteristics. His periodic chart contained 63 elements in all. Later, his hypothesis was unable to organize every element. Henry Moseley, a scientist, revised the law of the periodic table in 1913 and organized the elements depending on their atomic numbers.

Dobereiner’s law of triads 

The “Triad” is a set of three elements that Dobereiner developed by grouping together elements with comparable qualities. By following their atomic masses, he organized three elements so that the mean of these elements’ atomic masses is the same as the mass of the middle elements. For instance, he placed elements with atomic weights of 6.9, 23, and 39 together, including lithium (Li), sodium (Na), and potassium (K). Their average atomic mass, which is 23, is the same as that of sodium. However, he only could put together three of these groups using the known elements, for which his theory of triads was inaccurate.

Newland’s law of octaves

On his table, he arranged about 56 recognized elements.  He discovered that each eighth element had a property in common with the first element. He, therefore, equated the elements to musical octaves. Newland’s law of octaves is the name given to his hypothesis because of this.

The eighth element after sodium is potassium, which shares several characteristics with sodium. As a result, they are organized in a single column. He placed several elements in the same category like nickel and cobalt, as well as chlorine and bromine, which do not match any qualities with nickel and cobalt.

Mendeleev’s periodic law

The atomic mass influences the properties, according to Mendeleev’s periodic law. This suggests that when the elements are organized in the sequence of their atomic weights, the physical and chemical characteristics of the elements repeat periodically. The periodic table refers to Mendeleev’s arrangement of the previously known elements in a sequence of increasing atomic masses. Columns are rows, placed vertically that include elements of the same features. Periods was the term used for the rows, placed horizontally.

The modified version of the periodic table

Mendeleev’s periodic law was revised by Henry Moseley in 1913 with the help of atomic numbers of different elements. He claimed that an element’s atomic number has a significant impact on how other elements are organized.

According to him, an element’s characteristics are periodic factors of its atomic number instead of its atomic mass. Moving from one element to the next increases the atomic number of molecules. So, using their rising order of atomic numbers as a guide, he organized the elements.

His hypothesis produced the Modern Periodic table by addressing the flaws in Mendeleev’s Periodic Table. In 7 horizontal and 18 vertical columns, he organized the elements into periods and groups accordingly.

Now that you’ve explored the fascinating history of the periodic table and the remarkable contributions of Dmitri Mendeleev and Henry Moseley, we invite you to deepen your understanding and appreciation of all 118 elements and their symbols, you won’t want to miss this comprehensive guide!

Drawbacks of modern periodic laws

1. Doubts remain about the location of hydrogen, specifically whether it belongs to the IA group or the VIIA group. Elements’ isotopes have no location in the modern periodic table.
2. Actinides and Lanthanides are not listed in the Current Periodic Table and are preserved discreetly under the table.
3. The basis of the law of the periodic table, or the isolation of related elements, was not addressed by the current periodic table. Some unrelated elements have been combined.

Summary

The History and development of the modern periodic table are described here. Numerous scientists like Dobereiner, Newland, and Mendeleev did much research on the periodic table but they faced failure. But later Mendeleev’s periodic table was modified and it went with all the scientific logic. According to this modern periodic table, all the elements are listed in increasing order of their atomic numbers. There are 7 horizontal columns termed as periods and 18 vertical columns depicted as groups. From the modern periodic table, we get an idea about the chemical and physical characteristics of all the elements. Depending on this, the order of size, ionization energy, enthalpy, electron affinity, etc. can be determined properly.

Frequently Asked Questions

1. What element is the least popular?

Ans: Although astatine (At), a member of the halogen family that also comprises fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), may serve as the least common naturally occurring element in the Earth. It is assumed that it exhibits similar features to other Group 17 elements.

2. What does modern periodic law state? 

Ans: “The chemical and physical characteristics of the elements are periodic effects of their atomic numbers,” is how the current Periodic law is best represented. The proton number or electron number is the same as their atomic number in the case of neutral atoms. 

3. Who designed the modern periodic table?

Ans: To create the current periodic table Neils Bohr, took the idea of the current periodic law that states “the properties of the elements are periodic functions of their atomic numbers,”. It is often referred to as a lengthy periodic table. The current periodic law served as the foundation for its creation. Henry Moseley proposed this periodic law.

Introduction

The ozone layer is like a savior for earth and mankind. It acts as a protective covering around the surface of the earth. It makes us safe from the ultraviolet (UV) radiation coming from the sun which directly hits the earth’s surface. The Ozone layer is situated at the end of the second layer of our earth’s atmosphere i.e. in the stratosphere. It gets damaged by various free radicals around us i.e. nitric oxide (NO), atomic bromine (Br), atomic chlorine (Cl), a hydroxyl group (OH), etc. These radical catalysts boost the depletion rate by many folds. Continuous damage to the ozone layer is causing serious health effects on the whole earth. As a result, UV radiation absorbing capacity is decreasing rapidly. 

Define Ozone layer 

It is a layer of protective covering formed by a molecule O3 around our earth’s atmosphere ranging from 15-30 km. This saves us from life-threatening harmful ultraviolet (UV) radiation emitted by the sun. The ozone (O3) can absorb that radiation and give us a safe surrounding to live in. Among several layers of the earth, the second layer i.e. stratosphere contains the maximum density of this ozone layer as compared to any other atmospheric layer of the earth. This discovery of this ozone layer was in the year of 1913 by two French physicists Charles Fabry and Henri Buisson. It is assumed to absorb 95-97 % of the medium and little high-frequency radiation coming from the sun. 

What is the depletion of the ozone layer? 

Depletion of the ozone layer means degrading the layer formed by the ozone(O3) molecule around our atmosphere. This restricts the amount of harmful cosmic rays and radiation from the sun. Day by day the thickness of this layer is getting reduced and also holes are forming at many places due to the heavy damage of ozone molecules. It is more observed at both poles of the earth. Due to the irresponsible behavior of mankind, various chlorine (Cl) containing substances get released into the earth. They rise above and react with O3 and degrade it. It is also thought that one Cl atom can degrade around a lakhs of ozone (O3) molecules. Substances like chlorofluorocarbons (CFC) from refrigerators, carbon tetrachloride, hydrochlorofluorocarbons, etc. are highly responsible for such heavy damage. 

Factors responsible for the depletion of the ozone layer

• Nitric oxide (NO), nitrous oxide (N2O), and nitrogen dioxide (NO2) are among the nitrogenous chemicals that have a significant impact on the ozone layer’s depletion or breakdown.
• Solvents, freezers, spray aerosols, air conditioners (A.C.), and other devices emit chlorofluorocarbons, which is one of the leading reasons for the ozone layer depletion represented by CFCs. Ultraviolet (UV) radiation in the stratosphere decomposes chlorofluorocarbon molecules, releasing chlorine (Cl) atoms in the process.
• The ozone layer molecules are also severely harmed by irregular or unmanaged rocket launches; in fact, these activities contribute more to the ozone layer’s destruction or depletion than CFCs do.

Effects of ozone layer depletion 

The environment and all life forms that exist on the surface of the earth are seriously impacted by the breakdown of the ozone layer which increases the amount of radiation reaching the earth’s surface. Eye failure, various forms of skin cancer, and the body’s immune disorders are some of these adverse effects. Both aquatic ecosystem and terrestrial ecosystem also impacted by harmful UV radiation.

Effects of ozone layer depletion on mankind

Humans are adversely affected by the breakdown of the ozone layer, including the following effects:

• It is well understood, the loss of the ozone layer can result in more ultraviolet (UV) radiation reaching the earth’s surface, which enhances the danger of skin cancer and may also cause eye cataracts and immune system damage.
• Melanoma, the most fatal form of skin cancer, can increase as a result of excessive UV light exposure.

Effect of the damaged ozone layer on animals

A few harmful effects on animals are as follows:

• Fish, frogs, and other marine species’ early or beginning embryonic phases have been known to be harmed by ozone layer loss.
• Animals’ capability to breed slows down as ozone layer depletion occurs.
• Small fish or marine species may experience colony declines even with a slight increase in UV exposure.

Effects of ozone depletion on plants

• Plant developmental and physiological functions are strongly impacted by ultraviolet light.
• The growth, adaptability, and repair of flora are impacted by these dangerous radiations.
• These damaging radiations can inhibit the nutrient cycle and lead to plant diseases.

Summary 

The area known as the earth’s stratosphere contains the ozone layer, also called the ozone screen. The majority or all of the ultraviolet (UV) rays from the sun are absorbed by this layer.   Free radical catalysts can damage the ozone layer. In recent decades, there has been a marked rise in the emission of greater quantities of chlorine (Cl) and bromine (Br) into the atmosphere. This is due to the reckless discharge of vast amounts of chlorofluorocarbons (CFCs) and bromofluorocarbons by irresponsible human activities. All these are affecting human and animal life in a very adverse manner. 

Frequently Asked Questions

1. How can the ozone layer be preserved?

Ans: Purchasing an air conditioner and refrigerator which doesn’t use HCFCs as a coolant. Also using perfumery products having no CFCs and HCFCs. It is mandatory to regularly check for any leakage in refrigerators and air conditioners.

2. Can humans survive in a world without ozone?

Ans: The shielding ozone, often known as the “ozone layer,” is essential to life. Radiation from the sun includes heat, light, and many other kinds of radiation. UV (ultraviolet) radiation exposure too much can injure both plants and animals as well as induce cataracts and skin cancer.

3. Where does ozone become hazardous to humans? 

Ans: Ozone is a colorless substance that, depending on its location, may be beneficial or harmful. Because it protects the planet from the sun’s UV radiation, the ozone found in the stratosphere is beneficial. Because it could be harmful to human health at the surface level, where we inhale. 

Introduction

The radioactive materials that exist in the environment cause radioactive pollution. Various environmental conditions that are dangerous to life, are generated by the improper handling of radioactive materials. It has numerous adverse effects on both people and animals as well as the environment. The government should adopt a variety of policies to decrease the effect of radioactive materials. The Chernobyl incident was among the most notable instances of radioactive pollution.

Define radioactive pollution

When radioactive compounds are released into the atmosphere during nuclear explosions, nuclear weapon testing, and nuclear weapon development, it causes real damage to living things and their surroundings. This is known as radioactive pollution.

Sources of radioactive pollution and their examples

1. Though rocks constitute the majority of background radiation, just a minor portion of it is produced by man-made items. Background radiation through naturally available radioactive minerals can be found in the soil, earth, and water. 
2. A number of these naturally occurring radioactive elements can be found in small amounts in the human body. 
3. And some examples of radioactive pollutants are radionuclides. They are the primary causes of emissions that result in the formation of beta particles, radioactive substances, gamma radiation, etc.

 Reasons for Radioactive pollution

1. The majority of human-caused radiation pollution was likely produced in the middle of the 20th century and it happened due to numerous research or operational nuclear explosions.
2. Low to medium radiation may be produced during the treatment and removal of nuclear materials over a long duration of time. The primary problem with hazardous materials is that they cannot be biologically or chemically decomposed or handled.

Application of Radioisotopes

There are two main applications of radioisotopes.

• Radioactive Materials Leakages:

Ships have occasionally run straight into the ground on coral reefs or glaciers, discharging contaminants into nearby rivers and the surroundings. Among the numerous of these substances, petroleum products have a high radiation concentration and can be harmful to the environment.

• Smoke-detecting equipment:

Smoke detectors of ionization type contain very small amounts of americium-241, which has a half-life of 458 years.

• Establishment of  Defensive Weapons:

Many deadly weapons are constructed of nuclear materials which cause radiation. Due to these, a serious health risk may occur.

Adverse effects of radioactive pollution

• Diseases caused by exposure to Radioactive Pollution:

The most common illness that appears in people who are exposed to radioactive pollution is cancer. Among the worst ailments caused by radioactive pollution are leukemia, anemia, and cardiovascular disorders.

• Cell damage and nuclear poisons:

Cell development may be influenced in several ways by radioactive exposure. Living creatures have different bodies made up of millions of cells, every of which performs a specialized function. It has been shown that radioactive pollution can alter pre-existing cells and harm tissues and organs permanently. Situations of high radiation exposure usually result in fatalities and chronic illnesses.

• Burns:

Although radiation is uncomfortable to endure, you can easily tell whether it has had an impact on you. The sudden appearance of blisters and burns serves as evidence. This leads to skin cancer, which can complicate the condition.

• Ruins plant growths: 

The land can be significantly contaminated by improper disposal of radioactive materials. This type of waste is radioactive, and when it interacts with soil components, it can turn the soil exceedingly hazardous and unusable.

🌍 Discover powerful strategies to combat air pollution in our latest article on “Air Pollution Control.”

Prevention of Radioactive pollution

1. Radioactive substances can’t be decomposed easily by any means of chemical or biological process. So during research on plants, chemical or biological products and radioactive substances are separated properly.
2. Radiation waste confinement is done in far-off places, such as distant caves or deserted mines, which also require the deployment of barriers of some sort.
3. Non-radioactive methodologies can be applied to carry out several frequently utilized tests in the biomedical discipline.

Summary

Every animal on this planet and the ecosystem is severely harmed by radioactive particles. Radioactive pollution is caused due to the contamination of air or water with radioactive elements such as uranium, potassium, radium, and many more. These pollutants endanger people and their lives. The extent of radioactive contamination is based on the number of radioactive waste produced. Strong radioactive materials are the most potent type of waste and can be generated by substances like uranium, which again is consumed in nuclear reactors.

Frequently Asked Questions

1. How does the human body react to radiation?

Ans: The DNA in human cells can be harmed by radiation. Acute Radiation Syndrome (ARS) can be caused due to high exposure to radiation. High levels of radiation exposure may potentially cause cancer.

2. What is the amount of radiation present in bananas?

Ans: Radiation of.01 millirem (0.1 microsieverts) can be generated by one banana. There is incredibly little radiation present here. So one would have to consume around 100 bananas to be exposed to the equivalent level of radiation that an American would experience daily from atmospheric radiation.

3. Which radiation is the most dangerous?

Ans: The most dangerous radiation kinds include those that damage DNA, such as gamma and x-rays. Despite the presence of clothing, X-rays and gamma rays can totally penetrate the body and harm DNA or cells. Compared to X-rays, gamma rays are substantially more dangerous.

Introduction

Organic compounds are those in which one or more than one carbon atom is connected with other elements like hydrogen, oxygen, or nitrogen via covalent bonds. These organic molecules can be divided based on their structure and the presence of different functional groups. Methane is the smallest organic compound. 

Classification of organic compounds

 Organic compounds, mainly hydrocarbons can be divided into two parts: 

1. Aliphatic hydrocarbons 
2. Aromatic hydrocarbons.

• Aliphatic hydrocarbons: These are the compounds, drawn in an open-chain format. They never form any ring as they form linear structures. They can be classified into two types:
• Saturated compounds. 
• Unsaturated compounds. 
• Saturated compounds: Saturated compounds are those in which two carbon atoms are linked together only via a single bond. Alkane falls under this category. 

1. Alkane: In this type of structure, C atoms form single bonds with the H atoms. For example Methane, Ethane, Propane, Butane, etc.

\[\begin{array}{l}Methane:C{H_4}\\Ethane:{\rm{ }}{C_2}{H_6}\\Propane:{\rm{ }}{C_3}{H_8}\\Butane:{\rm{ }}{C_4}{H_{10}}\end{array}\]

Physical characteristics of Alkane:

1. Alkanes are colorless and the density of alkanes is very low.
2. The alkanes, containing a lower number of carbon atoms, have lesser boiling and melting point. But with an increase in the number of carbon atoms in hydrocarbons, melting and boiling point increases.
3. Alkanes are non polar. So they always tend to be dissolved in nonpolar solvents.

Chemical properties of Alkane:

1. The reactivity of alkanes is very low.
2. Alkane doesn’t react with any kind of strong acids or bases. It is also unreactive toward any reducing or oxidizing agent.
3. Alkanes are combustible and produce heat.
4. Alkanes can undergo reactions with halogens only in presence of UV light.

Unsaturated compounds: In unsaturated compounds, two adjacent carbon atoms are joined together by a double bond or a triple bond. The addition of hydrogens to unsaturated hydrocarbons leads to the formation of saturated hydrocarbons. They are classified into two groups:  

1. Alkene 
2. Alkyne

Alkene: Compounds that hold one or more double bonds between two carbon atoms are called alkenes. For Example Ethylene, Propyne, etc.

\[\begin{array}{*{20}{l}}{Ethylene:{\rm{ }}{C_2}{H_4}}\\{Propene:{\rm{ }}{C_3}{H_6}\;\;}\end{array}\] 

Physical characteristics of alkene

1. The first three alkene group members are gaseous, the following fourteen are liquids, and the final three alkenes are solids. 
2. Like alkanes, alkenes are nonpolar and dissolve in highly non-polar solvents like benzene, 
3. With an increase in the number of carbon atoms in alkenes, the boiling point increases.  Similar to alkanes, straight-chain alkenes have a higher point of boiling than branched-chain alkenes.
4. The arrangement of the molecules impacts the melting points of alkenes. However, the melting point of the trans isomer is higher than cis.  

Chemical features of alkenes

1. Alkenes undergo addition reactions with hydrogen molecules, halogens, and water molecules.
2. Alkenes are more reactive than alkanes. Alkenes burn at a much faster rate with oxygen.

Alkyne: The compounds that contain one or more than one triple bond are called alkyne systems. For example Acetylene, Propyne, etc.

Physical properties of alkyne

1. Alkynes are unsaturated, nonpolar hydrocarbons with characteristics that are identical to those of alkanes and ketones.
2. Alkynes are insoluble in water, weakly soluble in polar solvents, and soluble in organic solvents.
3. Alkynes have a somewhat larger boiling point than alkanes and alkenes.
4. Due to the linear structures of alkynes, the molecules are very closely arranged. So their melting point and boiling point are higher than alkane and alkyne.

Chemical properties of alkynes

1. It can undergo addition reactions with electrophilic substances like HCl or HBr and Br2, I2, etc.
2. The additional pi bonds in alkynes, then alkenes, make them the most reactive. towards chemical reactions.
3. Due to the linear structures of alkynes, the molecules are very closely arranged. 

Aromatic hydrocarbons: These hydrocarbons contain sigma bonds along with the delocalization of pi electrons in a cyclic rearrangement. It is another kind of unsaturated compound. For example Benzene.

Characteristics of Aromatic compounds:

1. These are cyclic and planar in structure.
2. They consist of only carbon and hydrogen atoms. The double bonds are conjugated in these structures.
3. These compounds possess a unique odor or aroma. So they are called aromatic.
4. They are nonpolar and due to their un reactivity, they are used as a solvent for dissolving non-polar compounds.
5. They are more volatile than aliphatic compounds.

Difference between aliphatic and aromatic hydrocarbons

Summary

Organic compounds mainly hydrocarbons can be classified into two groups; Aliphatic and Aromatic. Aliphatic compounds are of two types; saturated and unsaturated. Alanes fall under the category of saturated hydrocarbons whereas alkenes and alkynes are part of unsaturated hydrocarbons. There is a large difference between aliphatic and aromatic compounds based on their chemical and physical characteristics. Classification of organic compounds is really important. As different types of organic compounds have different chemical properties, hence they can participate in the reaction with the same chemicals but follow different mechanistic steps. So to determine the mechanism of any reaction, we need to know about different kinds of organic molecules. That is why the classification of organic compounds is one of the most important topics for chemists.

Frequently Asked Questions

1. What is the drawback of the classification of organic compounds?

Ans: Carbonate and cyanide salts are also carbon-containing compounds. But the compounds like hydrogen cyanide and carbon dioxide are not considered to be organic molecules. This is the drawback of the classification of organic compounds.

2. What are the necessary features of an organic compound?

Ans: The compounds in which carbon atoms are covalently linked with hydrogen, nitrogen, and oxygen atoms are called organic compounds. In hydrocarbons, carbon atoms are linked with hydrogen atoms only.

3. Which organic molecule provides energy?

Ans: Carbohydrate compounds can provide energy. For example, a monosaccharide like Glucose can provide energy very fast as it can be digested quickly.

Introduction

Natural fibres are fibres derived from plants and animals that have a wide range of applications in the production of composite materials. Most natural fibres are thought to be effective sweat and moisture absorbers, and different natural fibres can provide a wide range of textures.

What are Fibres?

Fibres are materials used in the production of textiles such as clothing and cables. All textiles contain natural or synthetic fibres. Natural fibres are made from natural sources such as animals and plants. Synthetic fibres are created through chemical synthesis.

Types of Fibres

1. Synthetic Fibres

Synthetic fibres, also known as man-made or artificial fibres, are manufactured through chemical synthesis and were first developed in the nineteenth century.

2. Natural Fibres

Natural fibres are derived from animals and plants, and they are frequently treated and spun into yarn before being turned into a product.

Examples of Natural Fibres

1. Cotton is derived from cotton seeds and is widely used in textiles. It is extremely lightweight, making it an ideal fibre for garment fabrics, and this has increased consumer demand.
2. Silk is derived from an insect and is the material used to make a cocoon.
3. Jute is a stronger fibre than cotton and jute, derived from plants, and it is used to make sacks and other packing materials.
4. Wool is derived from sheep and other hairy animals and is used to make fabrics due to its ability to retain heat. Wool is also a popular clothing fibre because it is preferred by people who live in cold climates.

Check out online study options are a great way to clear the science concepts you need. Study Science tuition for classes 8th Lesson 3.

Advantages of Natural Fibres

1. Natural fibre clothing is significantly more pleasant to wear than synthetic clothing, especially during the summer, when people sweat more and just need clothing made of breathable materials that can soak the extra water.
2. Natural fibres are excellent insulators because they can trap air between them, preventing them from escaping into the atmosphere. This air, which is captured in the fabric’s microscopic holes, provides warmth and helps keep a person’s body temperature constant even in cold weather, which is why many skiers, hikers, and other people who live in cooler environments prefer to wear silk or wool.

The disadvantages of Natural Fibres

1. Natural fibres are generally more expensive than synthetic fibres due to their qualities as a wonderful insulator, being much more sustainable, and much more comfortable to wear, and because they are retrieved directly from the environment, the cost of producing them is often higher than the price of producing synthetic fibres.
2. Natural fibre production is not always completely under human control, and nature is autonomous and does not work by human requirements and aspirations. Natural disasters and tragedies have a significant impact on availability, causing significant variations in supply and price.

Summary

Natural fibres can be derived from both plants and animals and are used in a wide range of composite material production processes. Wearing natural fibre clothing is more comfortable than wearing synthetic fibre clothing. Synthetic fibres, which are produced through chemical synthesis, are also referred to as artificial fibres. 

Frequently Asked Questions

1. Why are natural fibres such good insulators?

Ans. Natural fibres can trap air between them, preventing them from escaping into the atmosphere. Even in extreme cold, the trapped air keeps a person warm and regulates their body temperature. Because of this, natural fibres are said to be excellent insulators.

2. Why are synthetic fibres so simple to make?

Ans. Synthetic fibres can be produced in greater quantities and at a lower cost than natural fibres, as well as faster in a factory.

3. What advantages do cotton fabrics have over synthetic fabrics?

Ans. Synthetic fibres are not suitable for hot and humid conditions because they do not absorb sweat as well as cotton garments, but cotton garments do. The cotton cloth absorbs water quickly and burns at a low temperature.