Math Is Fun Forum

Cold Quotes - IV

1. Living indoors without fresh air quickly poisons the blood and makes people feel tired and seedy when they don't know why. For myself, I sleep out of doors in winter as well as summer. I only feel tired or seedy when I have been indoors a lot. I only catch cold when I sleep in a room. - Robert Baden-Powell

2. Here at the Cold Spring Harbor Laboratory, we have genetically rearranged various viruses and bacteria as part of our medical research. In fact, we have been able to create entirely new types of DNA molecules by splicing together the genetic information from different organisms - recombinant DNA. - James D. Watson

3. If a patient is cold, if a patient is feverish, if a patient is faint, if he is sick after taking food, if he has a bed-sore, it is generally the fault not of the disease, but of the nursing. - Florence Nightingale

4. A small cold and cough can actually stop you from going where you are. - P. V. Sindhu

5. I can see that, without being excited, mathematics can look pointless and cold. - Maryam Mirzakhani

6. The smartest thing I did was to stop going online. I'm the sort of person who will just look for the negative - Michael really can't understand it, but that's just the way I am. And with my bipolar thing, that's poison. So I just stopped. Cold turkey. And it's so liberating. - Catherine Zeta-Jones

7. I get cold really quickly, but I don't care. I like weather. I never understand why people move someplace so that they can avoid weather. - Holly Hunter

8. Would not the child's heart break in despair when the first cold storm of the world sweeps over it, if the warm sunlight of love from the eyes of mother and father did not shine upon him like the soft reflection of divine light and love? - Max Muller.

Thermal Power

Gist

Thermal power is electricity generated by converting heat energy into mechanical and then electrical energy, typically by burning a fuel to boil water into steam. The steam spins a turbine, which is connected to a generator that produces electricity. Sources for this heat can include coal, natural gas, oil, and geothermal or biomass energy.

Thermal power is electricity generated by converting heat energy into mechanical energy, which then drives a generator. The process typically involves heating a fluid like water to create steam, which spins a turbine. This steam is then condensed back into water and reused.

Summary

Thermal power refers to the energy that is generated by converting heat into electricity. It is the process of producing electricity from a primary source of heat by using a steam turbine, which drives an electrical generator.

The primary source of heat can be obtained from various sources, including burning fossil fuels such as coal, oil, and natural gas, or through nuclear fission.

The heat energy is used to produce steam, which is then directed towards the turbine.

The steam expands as it passes through the turbine blades, causing them to spin and generating electricity.

The electricity is then transmitted to the power grid for distribution to homes and businesses.

Thermal power is a widely used method of generating electricity due to the abundance and accessibility of fossil fuels.

However, it is also a significant contributor to greenhouse gas emissions and environmental pollution.

Efforts are being made to reduce the environmental impact of thermal power by developing more efficient and cleaner energy technologies such as solar, wind, and geothermal power.

Details

A thermal power station, also known as a thermal power plant, is a type of power station in which the heat energy generated from various fuel sources (e.g., coal, natural gas, nuclear fuel, etc.) is converted to electrical energy. The heat from the source is converted into mechanical energy using a thermodynamic power cycle (such as a Diesel cycle, Rankine cycle, Brayton cycle, etc.). The most common cycle involves a working fluid (often water) heated and boiled under high pressure in a pressure vessel to produce high-pressure steam. This high pressure-steam is then directed to a turbine, where it rotates the turbine's blades. The rotating turbine is mechanically connected to an electric generator which converts rotary motion into electricity. Fuels such as natural gas or oil can also be burnt directly in gas turbines (internal combustion), skipping the steam generation step. These plants can be of the open cycle or the more efficient combined cycle type.

The majority of the world's thermal power stations are driven by steam turbines, gas turbines, or a combination of the two. The efficiency of a thermal power station is determined by how effectively it converts heat energy into electrical energy, specifically the ratio of saleable electricity to the heating value of the fuel used. Different thermodynamic cycles have varying efficiencies, with the Rankine cycle generally being more efficient than the Otto or Diesel cycles. In the Rankine cycle, the low-pressure exhaust from the turbine enters a steam condenser where it is cooled to produce hot condensate which is recycled to the heating process to generate even more high pressure steam.

The design of thermal power stations depends on the intended energy source. In addition to fossil and nuclear fuel, some stations use geothermal power, solar energy, biofuels, and waste incineration. Certain thermal power stations are also designed to produce heat for industrial purposes, provide district heating, or desalinate water, in addition to generating electrical power. Emerging technologies such as supercritical and ultra-supercritical thermal power stations operate at higher temperatures and pressures for increased efficiency and reduced emissions. Cogeneration or CHP (Combined Heat and Power) technology, the simultaneous production of electricity and useful heat from the same fuel source, improves the overall efficiency by using waste heat for heating purposes. Older, less efficient thermal power stations are being decommissioned or adapted to use cleaner and renewable energy sources.

Thermal power stations produce 70% of the world's electricity. They often provide reliable, stable, and continuous baseload power supply essential for economic growth. They ensure energy security by maintaining grid stability, especially in regions where they complement intermittent renewable energy sources dependent on weather conditions. The operation of thermal power stations contributes to the local economy by creating jobs in construction, maintenance, and fuel extraction industries. On the other hand, burning of fossil fuels releases greenhouse gases (contributing to climate change) and air pollutants such as sulfur oxides and nitrogen oxides (leading to acid rain and respiratory diseases). Carbon capture and storage (CCS) technology can reduce the greenhouse gas emissions of fossil-fuel-based thermal power stations, however it is expensive and has seldom been implemented. Government regulations and international agreements are being enforced to reduce harmful emissions and promote cleaner power generation.

Types of thermal energy

Almost all coal-fired power stations, petroleum, nuclear, geothermal, solar thermal electric, and waste incineration plants, as well as all natural gas power stations are thermal. Natural gas is frequently burned in gas turbines as well as boilers. The waste heat from a gas turbine, in the form of hot exhaust gas, can be used to raise steam by passing this gas through a heat recovery steam generator (HRSG). The steam is then used to drive a steam turbine in a combined cycle plant that improves overall efficiency. Power stations burning coal, fuel oil, or natural gas are often called fossil fuel power stations. Some biomass-fueled thermal power stations have appeared also. Non-nuclear thermal power stations, particularly fossil-fueled plants, which do not use cogeneration are sometimes referred to as conventional power stations.

Commercial electric utility power stations are usually constructed on a large scale and designed for continuous operation. Virtually all electric power stations use three-phase electrical generators to produce alternating current (AC) electric power at a frequency of 50 Hz or 60 Hz. Large companies or institutions may have their own power stations to supply heating or electricity to their facilities, especially if steam is created anyway for other purposes. Steam-driven power stations have been used to drive most ships in most of the 20th century. Shipboard power stations usually directly couple the turbine to the ship's propellers through gearboxes. Power stations in such ships also provide steam to smaller turbines driving electric generators to supply electricity. Nuclear marine propulsion is, with few exceptions, used only in naval vessels. There have been many turbo-electric ships in which a steam-driven turbine drives an electric generator which powers an electric motor for propulsion.

Cogeneration plants, often called combined heat and power (CHP) facilities, produce both electric power and heat for process heat or space heating, such as steam and hot water.

Additional Information:

What are the key components of a thermal power plant?

The key components of a thermal power plant include:

* Boiler: This is the part of the plant where fuel is burned to produce high-pressure steam.
* Turbine: The steam produced by the boiler is used to power a turbine. The turbine is a machine that converts the kinetic energy of steam into mechanical energy.
* Generator: The mechanical energy produced by the turbine is used to generate electricity. The generator is a machine that converts mechanical energy into electrical energy.
* Condenser: After the steam passes through the turbine, it is cooled and condensed back into water by passing it through a condenser. The condenser transfers the heat from the steam to a cooling medium, typically water or air.
* Cooling tower: The water used in the condenser is typically cooled in a cooling tower before being returned to the condenser.
* Fuel storage and handling system: This is the system that stores and transports the fuel to the boiler. The fuel can be coal, natural gas, or oil.
* Ash handling system: The ash produced during the burning of fuel in the boiler is collected and transported to an ash handling system.
* Control system: The control system monitors and controls the various processes in the power plant, such as the flow of fuel, steam, and water.

Overall, a thermal power plant is a complex system that requires a range of components and processes to work together in a coordinated manner to produce electricity efficiently and reliably.

Who are the largest users of thermal power globally?

The largest users of thermal power globally are countries with large populations and rapidly growing economies, such as China, the United States, India, and Japan.

These countries rely heavily on thermal power to meet their electricity demands due to their large industrial and manufacturing sectors, as well as their growing populations and urbanization.

According to the International Energy Agency (IEA), China is the largest producer of thermal power in the world, followed by the United States and India.

In 2020, thermal power accounted for around 68% of the total electricity generated in China, 63% in the United States, and 73% in India.

However, many countries around the world are increasingly shifting away from thermal power towards cleaner and more sustainable sources of energy, such as renewables, to reduce their greenhouse gas emissions and combat climate change.

Countries such as Germany, the United Kingdom, and Denmark, for example, have set ambitious targets to phase out thermal power and transition to renewable energy sources in the coming years.

Q: What did the frog order at McDonald's?
A: French flies and a diet Croak.
* * *
Q: Would octopus make a good fast food?
A: You must be squidding!
* * *
Q: Where do burgers like to dance?
A: At a meat ball!
* * *
Q: Did you hear about the time Billy Crystal took Meg Ryan to McDonalds?
A: It's "When Harry Fed Sally".
* * *
Q: How did the hamburger introduce his wife?
A: Meet patty (meat patty).
* * *

Covalent Bond

Gist

A covalent bond is a chemical bond where atoms share a pair of electrons to achieve a more stable configuration. This sharing creates an attractive force between the nuclei of the atoms and the shared electrons, holding the atoms together in a molecule. Covalent bonds typically form between nonmetals, and the result is either a small molecule with low melting and boiling points or a giant covalent structure with high melting and boiling points. 

A covalent bond is a chemical bond formed when two atoms share a pair of electrons to achieve stability. This sharing allows atoms to fill their outer electron shells, and the bond is the force of attraction between the nuclei of both atoms and the shared electrons. Covalent bonds typically form between two nonmetal atoms. 

Summary

A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full valence shell, corresponding to a stable electronic configuration. In organic chemistry, covalent bonding is much more common than ionic bonding.

Covalent bonding also includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding, agostic interactions, bent bonds, three-center two-electron bonds and three-center four-electron bonds. The term "covalence" was introduced by Irving Langmuir in 1919, with Nevil Sidgwick using "co-valent link" in the 1920s. Merriam-Webster dates the specific phrase covalent bond to 1939, recognizing its first known use. The prefix co- (jointly, partnered) indicates that "co-valent" bonds involve shared "valence", as detailed in valence bond theory.

In the molecule H2, the hydrogen atoms share the two electrons via covalent bonding. Covalency is greatest between atoms that have similar electronegativities, regardless of whether the elements are the same as each other. Covalent bonding that entails the sharing of electrons over more than two atoms is said to be delocalized.

Details

A covalent bond, in chemistry, is the interatomic linkage that results from the sharing of an electron pair between two atoms. The binding arises from the electrostatic attraction of their nuclei for the same electrons. A covalent bond forms when the bonded atoms have a lower total energy than that of widely separated atoms.

A brief treatment of covalent bonds follows. For full treatment, see chemical bonding: Covalent bonds.

Molecules that have covalent linkages include the inorganic substances hydrogen, nitrogen, chlorine, water, and ammonia (H2, N2, Cl2, H2O, NH3) together with all organic compounds.

A single line indicates a bond between two atoms (i.e., involving one electron pair), double lines (=) indicate a double bond between two atoms (i.e., involving two electron pairs), and triple lines (≡) represent a triple bond, as found, for example, in carbon monoxide (C≡O). Single bonds consist of one sigma (σ) bond, double bonds have one σ and one pi (π) bond, and triple bonds have one σ and two π bonds.

Covalent bonds are directional, meaning that atoms so bonded prefer specific orientations relative to one another; this in turn gives molecules definite shapes, as in the angular (bent) structure of the H2O molecule. Covalent bonds between identical atoms (as in H2) are nonpolar—i.e., electrically uniform—while those between unlike atoms are polar—i.e., one atom is slightly negatively charged and the other is slightly positively charged. This partial ionic character of covalent bonds increases with the difference in the electronegativities of the two atoms. See also ionic bond.

When none of the elements in a compound is a metal, no atoms in the compound have an ionization energy low enough for electron loss to be likely. In such a case, covalence prevails. As a general rule, covalent bonds are formed between elements lying toward the right in the periodic table (i.e., the nonmetals). Molecules of identical atoms, such as H2 and buckminsterfullerene (C60), are also held together by covalent bonds.

Lewis formulation of a covalent bond

The idea that two electrons can be shared between two atoms and serve as the link between them was first introduced in 1916 by the American chemist G.N. Lewis, who described the formation of such bonds as resulting from the tendencies of certain atoms to combine with one another in order for both to have the electronic structure of a corresponding noble-gas atom.

In Lewis terms a covalent bond is a shared electron pair.

In a Lewis structure of a covalent compound, the shared electron pair between the hydrogen and chlorine ions is represented by a line. The electron pair is called a bonding pair; the three other pairs of electrons on the chlorine atom are called lone pairs and play no direct role in holding the two atoms together.

Each atom in the hydrogen chloride molecule attains a closed-shell octet of electrons by sharing and hence achieves a maximum lowering of energy. In general, an incomplete shell means that some attracting power of a nucleus may be wasted, and adding electrons beyond a closed shell would entail the energetic disadvantage of beginning the next shell of the atom concerned. Lewis’s octet rule is again applicable and is seen to represent the extreme means of achieving lower energy rather than being a goal in itself.

A covalent bond forms if the bonded atoms have a lower total energy than the widely separated atoms. The simplest interpretation of the decrease in energy that occurs when electrons are shared is that both electrons lie between two attracting centres (the nuclei of the two atoms linked by the bond) and hence lie lower in energy than when they experience the attraction of a single centre.

Lewis structures of more complex molecules can be constructed quite simply by extending the process that has been described for hydrogen chloride.

In some older formulations of Lewis structures, a distinction was made between bonds formed by electrons that have been supplied by both atoms (as in H―Cl, where one shared electron can be regarded as supplied by the hydrogen atom and the other by the chlorine atom) and covalent bonds formed when both electrons can be regarded as supplied by one atom, as in the formation of OH− from O2− and H+. Such a bond was called a coordinate covalent bond or a dative bond and symbolized O → H−. However, the difficulties encountered in the attempt to keep track of the origin of bonding electrons and the suggestion that a coordinate covalent bond differs somehow from a covalent bond (it does not) have led to this usage falling into disfavour.

Resonance

The blending together of these structures is actually a quantum mechanical phenomenon called resonance. At this stage, resonance can be regarded as a blending process that spreads double-bond character evenly over the atoms that participate in it. In ozone, for instance, each oxygen-oxygen bond is rendered equivalent by resonance, and each one has a mixture of single-bond and double-bond character (as indicated by its length and strength).

Hypervalence

Lewis structures and the octet rule jointly offer a succinct indication of the type of bonding that occurs in molecules and show the pattern of single and multiple bonds between the atoms. There are many compounds, however, that do not conform to the octet rule. The most common exceptions to the octet rule are the so-called hypervalent compounds. These are species in which there are more atoms attached to a central atom than can be accommodated by an octet of electrons.

In Lewis terms, hypervalence requires the expansion of the octet to 10, 12, and even in some cases 16 electrons. Hypervalent compounds are very common and in general are no less stable than compounds that conform to the octet rule.

The existence of hypervalent compounds would appear to deal a severe blow to the validity of the octet rule and Lewis’s approach to covalent bonding if the expansion of the octet could not be rationalized or its occurrence predicted. Fortunately, it can be rationalized, and the occurrence of hypervalence can be anticipated. In simple terms, experience has shown that hypervalence is rare in periods 1 and 2 of the periodic table (through neon) but is common in and after period 3. Thus, the octet rule can be used with confidence for carbon, nitrogen, oxygen, and fluorine, but hypervalence must be anticipated thereafter. The conventional explanation of this distinction takes note of the fact that in period-3 elements the valence shell has n = 3, and this is the first shell in which d orbitals are available. (These orbitals are occupied after the 4s orbitals have been filled and account for the occurrence of the transition metals in period 4.) It is therefore argued that atoms of this and subsequent periods can use the empty d orbitals to accommodate electrons beyond an octet and hence permit the formation of hypervalent species.

In chemistry, however, it is important not to allow mere correlations to masquerade as explanations. Although it is true that d orbitals are energetically accessible in elements that display hypervalence, it does not follow that they are responsible for it. Indeed, quantum mechanical theories of the chemical bond do not need to invoke d-orbital involvement. These theories suggest that hypervalence is probably no more than a consequence of the greater radii of the atoms of period-3 elements compared with those of period 2, with the result that a central atom can pack more atoms around itself. Thus, hypervalence is more a steric (geometric) problem than an outcome of d-orbital availability.

Additional Information:

Covalent bonding occurs when pairs of electrons are shared by atoms. Atoms will covalently bond with other atoms in order to gain more stability, which is gained by forming a full electron shell. By sharing their outer most (valence) electrons, atoms can fill up their outer electron shell and gain stability. Nonmetals will readily form covalent bonds with other nonmetals in order to obtain stability, and can form anywhere between one to three covalent bonds with other nonmetals depending on how many valence electrons they posses. Although it is said that atoms share electrons when they form covalent bonds, they do not usually share the electrons equally.

Introduction

Only when two atoms of the same element form a covalent bond are the shared electrons actually shared equally between the atoms. When atoms of different elements share electrons through covalent bonding, the electron will be drawn more toward the atom with the higher electronegativity resulting in a polar covalent bond. When compared to ionic compounds, covalent compounds usually have a lower melting and boiling point, and have less of a tendency to dissolve in water. Covalent compounds can be in a gas, liquid, or solid state and do not conduct electricity or heat well. The types of covalent bonds can be distinguished by looking at the Lewis dot structure of the molecule. For each molecule, there are different names for pairs of electrons, depending if it is shared or not. A pair of electrons that is shared between two atoms is called a bond pair. A pair of electrons that is not shared between two atoms is called a lone pair.

Octet Rule

The Octet Rule requires all atoms in a molecule to have 8 valence electrons--either by sharing, losing or gaining electrons--to become stable. For Covalent bonds, atoms tend to share their electrons with each other to satisfy the Octet Rule. It requires 8 electrons because that is the amount of electrons needed to fill a s- and p- orbital (electron configuration); also known as a noble gas configuration. Each atom wants to become as stable as the noble gases that have their outer valence shell filled because noble gases have a charge of 0. Although it is important to remember the "magic number", 8, note that there are many Octet rule exceptions.

Single Bonds

A single bond is when two electrons--one pair of electrons--are shared between two atoms. It is depicted by a single line between the two atoms. Although this form of bond is weaker and has a smaller density than a double bond and a triple bond, it is the most stable because it has a lower level of reactivity meaning less vulnerability in losing electrons to atoms that want to steal electrons.

Double Bonds

A Double bond is when two atoms share two pairs of electrons with each other. It is depicted by two horizontal lines between two atoms in a molecule. This type of bond is much stronger than a single bond, but less stable; this is due to its greater amount of reactivity compared to a single bond.

Triple Bond

A Triple bond is when three pairs of electrons are shared between two atoms in a molecule. It is the least stable out of the three general types of covalent bonds. It is very vulnerable to electron thieves!