Author: Admin
-
Dalton Atomic Theory: Definition, Examples, and Types
Continue ReadingWhat is Dalton Atomic Theory?
Dalton atomic theory is based on two of the well-known laws:
• The law of conservation of mass
• Law of constant composition.
The law of conservation of mass was formulated by Antoine Lavoisier states that matter can neither be created nor it can be destroyed in a closed system.
This means in a chemical reaction, the amount of each element involved in the given reaction must be the same as in the starting materials (reactants) and the products. This law of conservation of mass is used every time to balance chemical equations.
While researching about the same, Dalton also discovered that some gases having the same common element in given compounds could only be combined in certain proportions. Thus, he formulated the law of constant composition.
Postulates of Dalton Atomic Theory
The postulates of Dalton Atomic Theory are mentioned below;
• The matter is composed of atoms, and these atoms are the undividable building blocks of matter and thus cannot be destroyed.
Dalton theorized that the law of conservation of mass and the law of definite proportions could be described using the knowledge of atoms.
He proposed that all matter is made of tiny undividable particles which are known as atoms, and he assumed them as solid, hard, impassable, movable particles.
• The properties of all the atoms of an assumed element have the same mass. This can also be defined as the atoms of a given element have identical mass whereas the atoms of different elements have different masses.
Dalton projected that every single atom of an element, for instance, gold, is as same as every other atom of that particular element. He also stated that the atoms of one particular element vary from the atoms of all other elements.
For example; a sodium atom is very different from a given carbon atom. Elements may share few similar properties such as boiling points, melting points, etc. but no two elements can have the same set of exact properties.
• The Compounds are formed through different whole-number combinations of given atoms. In the next part of Dalton atomic theory, he theorized that compounds are the groupings of two or more different types of atoms.
For instance; the compound is table salt or NaCl. Table salt is a mixture of two separate elements the first is sodium which is a highly reactive metal and the second is chlorine which is a toxic gas.
When they react, the given atoms combine in a ratio of 1:1 to form white crystals thus forming table salt.
• A chemical reaction always results in the rearrangement of atoms of a given compound in the reactant and product formed.
In this part of Dalton’s atomic theory, he suggested that chemical reactions don’t terminate or create atoms. They just reorganize the atoms of compounds.
• Atoms of the same element usually combine to form two or more compounds in more than one ratio.
• The atom is thus the tiniest unit of matter and takes part in a different chemical reaction.
Advantages of Dalton Atomic Theory
• The three given laws were not exploited by Dalton; The law of multiple proportions, the law of conservation of mass, and the law of constant proportions
• The Dalton Atomic Theory also provides a basis to distinguish between elements and compounds.
Limitations of Dalton Atomic Theory
• Dalton atomic theory does not account for subatomic particles. Dalton atomic theory proposed that the atoms were undividable. Though, the discovery of subatomic particles (for instance, protons, electrons, and neutrons) refuted this postulate. Of Dalton.
• This theory fails to explain the existence of isotopes: Dalton atomic theory stated that all atoms present in the given element have identical masses and densities. Though, this postulate was disapproved as different isotopes of elements have different atomic masses
For instance: isotopes of hydrogen are; hydrogen, deuterium, and tritium.
• Dalton atomic theory fails to explain isobars also. This theory of Dalton states that the masses of the given atoms of two different elements must vary. Thus, two different elements can have the same mass number. Such atoms are known as isobars.
For Instance: 40Ar and 40Ca.
• This theory of Dalton does not account for allotropes as well.
For instance; the differences in the properties of diamond and graphite, containing a single atom of carbon, cannot be described by Dalton’s atomic theory.
In spite of of these drawbacks, Dalton atomic theory is generally true, and it forms the basis of modern chemistry.
Dalton Atomic Theory Citations
- John Dalton and the origin of the atomic theory: reassessing the influence of Bryan Higgins. Br J Hist Sci . 2017 Dec;50(4):657-676.
- A letter signed: the very beginnings of Dalton’s atomic theory. Ambix . 2010 Nov;57(3):301-10.
- Atomic Theory and Multiple Combining Proportions: The Search for Whole Number Ratios. Ann Sci . 2015 Apr;72(2):153-69.
Share
Similar Post:
-
Law of Definite Proportions: Definition, Examples, and...
Continue ReadingWhat is Law Of Definite Proportions?
This law of definite proportions is the basis for the study of stoichiometry in Chemistry.
The law of constant proportions states that chemical compounds are made up of elements that are present in a fixed ratio in terms of their mass.
This specifies that any pure sample of a compound, (no matter what is the source of that compound), will always encompass the same elements that are present in a similar ratio by their mass.
The Law of Definite Proportions also shows that whatever the quantity of water is, whether it be 4 moles or 72 grams, the ratio of the amount of hydrogen to oxygen by its weight will always remain the same, just like that of egg:sugar: butter ratio in the chocolate cake is always constant to maintain the delicious taste of the cake.
Law of Definite Proportions Examples
• For instance, in a nitrogen dioxide (NO2) molecule, the ratio of the number of nitrogen atoms present in given compound and oxygen atoms is 1:2 always. This ratio between the nitrogen and oxygen molecules would always remain the same.
• Salt which is written as the chemical compound NaCl comprises of atoms of Sodium (Na) and Chlorine (Cl). Thus, to create salt the exact same proportions of sodium and chlorine must always be combined.
• Sulfuric acid comprises of the specific elements of hydrogen, sulfur, and oxygen. The chemical formula of sulfuric acid is written as H₂SO₄. Thus, to create sulfuric acid the same proportions of hydrogen, sulfur, and oxygen must be combined.
• Ammonia which is a common household item is made up of the elements of hydrogen and nitrogen. The chemical formula for Ammonia is written as NH3, meaning that there is one atom of nitrogen which is combined with 3 atoms of hydrogen. Anhydrous ammonia consists of 82% nitrogen and 18% hydrogen. Any other grouping of hydrogen and nitrogen would result in a completely different type of chemical compound.
Law of Definite Proportions Applications
The law of definite composition has applications of both the compounds;
• molecular compounds having a fixed composition
• whereas ionic compounds require certain ratios to achieve electrical neutrality
• There are certain exceptions to the law of definite composition. These compounds are thus known as non-stoichiometric compounds, and examples of the same include ferrous oxide
• Further, this law of definite composition does not justify for isotopic mixtures.
Law of Definite Proportions and Non-Stoichiometric Compounds / Isotopes
There exist certain non-stoichiometric compounds whose elemental composition can vary from one to another. Such kinds of compounds obey the Law of multiple proportions.
For example, the iron oxide, which may hold iron atoms between 0.83 and 0.95 for each of the oxygen atoms, and consequently comprise anywhere between a percentage of 23 and 25 oxygen by mass.
The ideal chemical formula is given as FeO, but because of the crystallographic vacancies, it is up to FeO.95O.
Basically, Proust’s measurements were not precise enough to spot such small differences. The element’s isotopic composition can also differ based on its source; therefore, its involvement in even a pure stoichiometric compound mass can vary.
This discrepancy can be used in radiometric dating since atmospheric, astronomical, crustal, oceanic, and deep Earth processes can concentrate limited environmental isotopes favorably.
With the hydrogen and its isotope exception, generally, the effect is slight, but it is assessable with modern-day instrumentation.
Law of Definite Proportions Citations
- The Law of Definite Proportions: Nature volume 84, page364 (1910)
- The Berthollet-Proust Controversy and the Law of Definite Proportions. Nature volume 50, pages149–150 (1894)
- How Important are the Laws of Definite and Multiple Proportions in Chemistry and Teaching Chemistry? – A History and Philosophy of Science Perspective. Science & Education volume 10, pages243–266 (2001)
Share
Similar Post:
-
Law of Chemical Combination: Definition, Types, and...
Continue ReadingWhat is Law of Chemical Combination?
Chemistry is the study of the change of a substance from one form to the other.
These transformations frequently occur as a result of the combination of two diverse types of matter.
The combination of various elements to form compounds is ruled by certain basic rules. These rules are stated as laws of chemical combination.
The law of chemical combination describes the basic principles that are followed when atoms and molecules interact.
This remarkable variety of interactions allows for a diverse variety of chemical reactions and compounds.
Though chemical reactions are complex yet they are all primarily ruled by some guiding laws of chemical combination, which lay the basis for the investigation or analysis of chemical reactions.
Law of Chemical Combination Rule
The combination of elements to form compounds is ruled by the five basic laws which are mentioned below:-
1. Law of Conservation of Mass.
2. Law of Definite Proportions.
3. Law of Multiple Proportions.
4. Gay Lussac’s Law of Gaseous Volumes.
5. Avogadro Law.
1. Law of Conservation of Mass
In 1789, this law of conservation of mass was framed by Antoine Lavoisier. In simple terms, this law of conservation of mass states that matter can neither be created nor it can be destroyed.
In other words, the total mass, that is, the sum of the mass of reacting mixture that is the reactants and the products formed always remains constant.
For instance; the Burning of wood Thus, when wood burns the mass of the dust, ashes, and fumes is always equal to the original mass of the charcoal and the oxygen present when it initially reacted.
So the mass of the product which is ashes and gases equals the mass of the reactant which is charcoal and oxygen.
2. Law of Definite Proportions
A French well-known chemist, Joseph Proust stated that the proportion of elements by mass in a given compound will remain the same at all times.
In simple terms, This law of constant proportions states that chemical compounds are made up of elements that are present in a fixed ratio in terms of their masses.
For example; A nitrogen dioxide (NO2) molecule is taken, thus, the ratio of the number of nitrogen atoms and oxygen atoms present in a given compound is 1:2 always. This ratio of 1:2 between the molecules of nitrogen and oxygen would always remain the same.
3. Law of Multiple Proportions
In 1803, This law of multiple proportions which was given by Dalton stated that if two elements combine to form more than one compound, the masses of these elements present in the reaction are defined in the ratio of small whole numbers.
For instance, the masses of molecules of oxygen is combined with a fixed mass of carbon in CO2 (carbon dioxide ) and CO (carbon monoxide) are 32 and 16, respectively. Consequently, these masses of oxygen display a simple ratio of 32: 16 or it can be written as 2: 1.
4. Gay Lussac Law of Gaseous Volumes
In 1808, Gay Lussac gave this law built on his observations. In simple words, Gay Lussac law or Amonton’s law states that the pressure exerted by a gas is directly proportional to the temperature of the gas when the mass is fixed and the volume is kept constant.
The mathematical expression of the above-given law can be inscribed as follows:
P ∝ T;
P = kT
Thus,
P/T = k
• P is as defined the pressure applied by the gas on the walls of its vessel
• T is defined as the absolute temperature of the gas
For example, when aerosol cans are kept under warm conditions they eventually burst, because by heating the aerosol can pressure of the contents increases ultimately causing the can to burst.
When a pressurized aerosol can for example a deodorant can or a spray-paint can is heated, the consequent increase in the pressure is applied by the gases on the walls of its vessel can result in a blast.
This is the reason why numerous pressurized bottles or vessels have alerting labels stating that the given vessel must be kept away from fire and should be stored in a cool atmosphere.
5. Avogadro’s Law
Avogadro anticipated this law in the year 1811. Avogadro’s law is a relationship between the volume of gas and the number of moles.
This law states that at a constant temperature and pressure the total number of atoms or molecules present in a gas is directly proportional to the volume employed by that gas.
This indicates that 4 litres of hydrogen will have the same number of molecules as 4 litres of oxygen assumed that both the gases are at the same temperature and pressure.
This equation is mentioned below;
V ∝ n
V= kn
or
k = V/n
V is defined as the volume of gas
n is defined as the number of moles present in a given gas
k is defined as the proportionality constant
For instance, A compressed pool tube becomes portable when the number of air particles inside the tube is decreased which in turn decreases its volume and makes it compact.
During inflation, when the tube is filled with air thus it increases the number of air molecules in it which in turn increases the volume and size of the pool tube.
Hereafter, Avogadro’s law can be useful to inflate or deflate the given pool tube as per our need.
Law of Chemical Combination Citations
Share
Similar Post:
-
Gay Lussac Law: Formula, Equation, Calculation, and...
Continue ReadingWhat is Gay Lussac Law?
The law is named after a French chemist and physicist named Joseph Gay-Lussac. He articulated this law in 1808.
In simple words, Gay Lussac law or Amonton’s law states that the pressure exerted by a gas is directly proportional to the temperature of the gas when the mass is fixed and the volume is kept constant.
Gay Lussac Law Equation
The mathematical expression of the given law can be written as follows:
P ∝ T; P=kT
Thus, P/T = k
• P is defined as the pressure exerted by the gas on the walls of a container
• T is defined as the absolute temperature of the gas
• k is defined as a proportionality constant.
Gay Lussac Law Examples
The heating gas in a sealed vessel causes its pressure to rise, whereas cooling a gas lowers or reduces its pressure.
The happens because the increasing temperature imparts thermal kinetic energy to the given gas molecules.
As a result when the temperature increases, molecules present in the gas collide more often with the walls of the vessel.
These increased collisions are perceived as increased pressure.
Gay Lussac Law Graph
The association between the pressure and absolute temperature of a given mass of gas present at a constant volume can be demonstrated graphically as shown below;
From the above graph, it can be seen that the pressure of a gas that is taken at constant volume decreases with temperature as this pressure is directly proportional to the temperature.
Gay Lussac Law Formula and Derivation
Gay Lussac law indicates that the ratio of the initial pressure and temperature is always equivalent to the ratio of the final pressure and temperature for molecules of gas having fixed mass and is kept at a constant volume.
This formula can be written as given below:
(P1/T1) = (P2/T2)
• P1 is defined as the initial pressure
• T1 is defined as the initial temperature
• P2 is defined as the final pressure
• T2 is defined as the final temperature
This expression is formed from the pressure-temperature proportionality law of gas molecules.
Since,
P ∝ T for gases,
Thus,
P1/T1 = k
(initial pressure/ initial temperature = proportionality constant)
P2/T2 = k
(final pressure divided by final temperature = proportionality constant)
Consequently,
P1/T1 = P2/T2 = k
Or this can be written as,
P1T2 = P2T1
Gay Lussac Law Examples
Here are few examples of Gay Lussac law observed in our everyday life:
I. The Pressure
Automobile tire pressure drops on a cold day and climbs on a hot day. After driving, the air pressure present in a car’s tires goes up. This happens because the frictional force present between the tires and the road causes the air which is present inside the tires to heat up.
This air present in tires cannot expand further because the tires have a fixed-volume container, Thus, the pressure increases. The above example defines Gay Lussac law clearly.
II. Pressure Cooker
When heat is applied to a pressure cooker it increases the pressure inside the cooker. Thus, the Increasing pressure leads to an increase in the boiling point of water, as a result, it shortens the cooking time.
As the temperature of the liquid water rise, thus leading to the formation of water vapour (that is water present in its gas state). This vapour cannot escape the pressure cooker as it is a closed container, which means the volume is constant.
At the higher temperature which is the normal boiling point of water (100°C) food can be cooked sooner
III. Aerosol Can
It is generally advised not to store the aerosol cans under warm conditions or because by heating the aerosol can pressure of the contents increases eventually causing the can to burst.
When a pressurized aerosol can for instance a deodorant can or a spray-paint can is heated, the subsequent increase in the pressure applied by the gases on the walls of the container can result in an explosion.
This is the reason why several pressurized bottles or containers have cautioning labels stating that the purchased container must be kept away from fire and should be stored in a cool environment.
IV. Water Heater
An electric water heater is a lot similar to a pressure cooker. A pressure-relief valve present in the water heater prevents the steam formed from accumulating.
If the valve present in the heater fails to function due to one reason or the other then the heat drives up the steam pressure inside the heater, ultimately bursting it.
Gay Lussac Law Limitations
The limitations of Gay Lussac law are as follows:
The Gay Lussac law is only valid to ideal gases.
Gay Lussac law holds moral for real gases either at high temperatures or low pressure.
Gay Lussac Law Citations
Share
Similar Post:
-
Law of Multiple Proportions: Example, Definition, and...
Continue ReadingWhat is Law of Multiple Proportions?
o The law of multiple proportion is also known as Dalton’s law which was proposed by English chemist and metrologist named John Dalton in 1804.
o This law was based on the observation of Dalton which states that when the elements combine to form two or more compounds the proportion of the elements in those chemical compounds can be articulated in this small whole number ratios.
o This is law of multiple proportions is also a part of the basis of modern atomic theory.
o This law of multiple proportion only applies to compounds which are composed of same elements.
o When SO2 and CO2 are taken together then one compound has sulfur (S) and one has carbon (C), thus, here the law of multiple proportions is not valid as compounds composed of only same elements is applicable to law of multiple proportions.
Postulates of Dalton's Atomic Theory
o All matter consists of tiny particles named atoms.
o Atoms cannot be created nor it can be destroyed.
o The atom is the smallest unit present in matter and take part in chemical reaction.
o Atoms of the same element are identical in their shape and mass.
o Atoms of different elements when combined in a constant ratio form compound.
o Atoms of the same element can also combine in more than one ratio to form different compounds
Law of Multiple Proportions Examples
o Assume two molecules of CO that is carbon monoxide and CO2 that is carbon dioxide
o CO contains 12 grams of carbon and 16 grams of oxygen
o CO2 contains 12 gram of carbon plus 32 grams of oxygen
o The ratio of mass of oxygen in each of the two compounds is expressed in the ratio 16 :32 which is equal to 1: 2
o Therefore, the law of multiple proportions is proved here.
o Another example of law of multiple proportions includes; Hydrogen and oxygen combine to form two compounds of H2O and one compound of hydrogen peroxide.
o Thus, the ratio of different weights of oxygen is 16 and 32 combining with a fixed weight of two hydrogen thus,16 I; 32 that is 1; 2 which is a simple whole number ratio.
o Therefore, Law of multiple proportions is proved here.
o Nitrogen reacts with oxygen to form numerous nitrogen oxides under various reaction conditions.
o Some of them include; nitrogen monoxide (NO), nitrogen dioxide (NO2), dinitrogen trioxide (N2O3), and dinitrogen pentoxide (N2O5).
o The amount of nitrogen taken is 14 g.
o When take the ratio of the amounts of oxygen that is required each reaction, thus the ratios obtained are 8:16:24:32:40 or 1:2:3:4:5.
o Thus, the ratio obtained is in small whole numbers and the given law of multiple proportions is also valid for more than two reactions.
Law of Multiple Proportions Limitations
o The existence of different isotopes of hydrogen like H1 or H2 causes differences. Thus, the same isotope should be used throughout the reaction for preparation of compounds.
o This law of multiple proportions fails often when heavy weight molecules are involved in the given reaction. Example for the same include biochemical reaction.
o Atomic masses of elements are not always in the whole number example the atomic mass of nitrogen. presumed to be 14 amu, but its value is 14.0067 amu. When the ratio of such number is taken, the results obtained are very large whole numbers.
o The law is valid only for normal reactions. It fails repeatedly when a non-stoichiometric compound is involved in the given reaction.
Law of Multiple Proportions Citations
Share
Similar Post:
-
What is Density? Formula, Calculation, Definition, and...
Continue ReadingWhat is Density?
o The principle of density was discovered by a Greek scientist named Archimedes.
o Density is a physical property that is defined as mass divided by its volume.
o Everything around us has mass, it is a fundamental property and plays a role in two other important properties which are volume and density.
o The SI unit of mass is kilograms or grams and it is a measure of the amount of matter present in an object.
o Volume is defined as a three-dimensional space that an object occupies it is expressed in cubic metre.
o Thus, Density is the ratio of mass to volume and the SI unit of density is expressed as kg per metre cube (kg/m3) or per gram per centimeter cube(g/cm3).
o By definition, density is the measurement of how closely or loosely a matter is packed into a certain volume.
Everyday Examples of Density
o Wood floats on water because it has less density than that of water.
o Helium balloons rise in the air because helium gas has less density as compared to that of surrounding air.
o Ice floating on water is also an example of density which can be attributed to the Archimedes principle.
o Oil spills- when an oil tanker leaks on ocean/water body the oil floats on the water since oil has less density as compared to that of water and this helps to clean up the oil spills from surface of the earth.
Factors Affecting Density
o Density differs according to temperature and pressure.
o Temperature: As the temperature rises, most substances enlarge or increase their volume.
o This results in the decrease in density.
o Similarly, when the temperature goes down, the density of the substance increases.
o Thus, density is inversely proportional to temperature.
o Pressure: As pressure rises, density increases.
o Similarly, when pressure decreases density decreases because the inter molecular force of attraction decreases.
o Thus, density is directly proportional pressure.
o To sum up the above statements, density is inversely proportional to temperature and directly proportional to pressure exerted on a substance.
Change of Phase
o Liquids are less dense as compared to solids because solids have densely packed particles whereas particles of liquid that can slide around.
o Example; Density of water at its freezing point is 0.999 g/cm3, whereas density of ice is 0.92 g/cm3.
o Gases are less dense as compared to liquids because the particles of are free and can move around.
o When a liquid changes into a gas, its volume rises vividly, thus reducing the density of the substance.
o Example; Water has a density of 1.03 g/cm3 at 100°C, whereas the density
Change in Volume
o The volume of a substance changes with change in its temperature and pressure. Thus, in turn, it changes the density of the substance.
Density of Water
o The density of pure water is taken as 1 g/cm3.
o The water density depends on the purity of water.
o As pure water is less dense as compared to the saline water.
o When the purity of water molecules decreases, the density of water increases.
o Contamination in the water interrupts the density of water.
o Due to contamination, the density of water rises and this change in density depends on the degree of contamination and the temperature.
o Water is also identified as the universal solvent and it is the key component of fluids found in all organisms.
o Water is profusely available on the Earth and is found in all forms that is gas, liquid and solid.
o When the temperature reduces, water changes into solid and when the temperature rises, water changes into gas.
o At the room temperature, water is present in the liquid state.
Why Density is Important?
o Density is significant because it defines whether the given substance will rise or sink.
o So, understanding density has main inferences for the motions of substances and gases in the atmosphere and materials floating or sinking in water (H2O).
o By determining of the densities of substances, help us in their separation techniques.
o For instance, separation of oil from the water.
o Another significant application of density is determining whether a substance will float on or will sink in water.
o Example for the same include the floating of ships and diving of submarines which happens due to their density difference.
Citations
Share
Similar Post:
-
Avogadro’s Law: Formula, Calculation, Definition, and Examples
Continue ReadingAvogadro's Law
In 1811, Avogadro’s law was described by a famous Italian chemist and physicist named Amedeo Avogadro. Avogadro’s law is a relationship between volume of gas and the number of moles.
This law states that at a constant temperature and pressure the total number of atoms or molecules present in a gas is directly proportional to the volume occupied by that gas.
Avogadro's Law Formula
This equation is given by;
V ∝ n
V=kn or k = V/n
V = volume of gas
n = Number of moles present in given gas
k = proportionality constant
The graphical representation of Avogadro’s law is given below;
The straight line indicates that the two quantities that are volume and number of moles present in gas are directly proportional to each other.
Thus, the straight line that passes through the origin signifies that 0 moles for gas will occupy zero space.
Avogadro's Law Calculation
Avogadro’s law can be derived from the ideal gas equation, which can be written as follows:
PV = nRT
• ‘P’ is defined as the pressure applied by the gas on the walls of container
• ‘V’ is defined as the volume occupied by the gas
• ‘n’ is defined as number of moles of gas present in given molecule
• ‘R’ is defined as the universal gas constant
• ‘T’ is defined as the absolute temperature of the gas
By reorganizing the ideal gas equation, the following equation can be obtained.
V/n = (RT)/P
Here, the value of (RT)/P is constant because pressure and temperature are constant according to Avogadro’s hypothesis and R is the universal constant.
Therefore,
V/n = k
Thus, the proportionality between the volume occupied by a gas and the number of molecules present in given gas is confirmed.
Avogadro’s Law Examples
Given below are few examples of Avogadro’s law;
I. Breathing
One of the finest example of Avogadro’s law is breathing. When we inhale, our lungs enlarge because they are filled with air. Similarly, when we exhale, the lungs let the air out and thus shrink in size. This change in volume is observed, which is proportional to the amount or the number of molecules of air confined by the lungs.
II. Inflating Tyres
The shape of a flat tyres gets distorted in the absence of air inside it. As soon as the flat tyres is filled with the required amount of air, it gets back to its original shape. Hence, the inflation of flat tyres is a clear example of Avogadro’s law in our everyday life.
III. Bicycle Pump Action
The pump abstracts the air from the environment and pushes it inside a flattened object. This increase in the amount of gas molecules in the object congruently changes its shape and helps it to enlarge. This example is clearly explained by Avogadro’s law.
IV. Pool Tube
A flattened pool tube becomes transportable as the number of air particles inside the tube is decreased which in turn reduces its volume and makes it compact.
During inflation, when the tube is filled with air, increasing the number of air molecules in it which in turn increases the volume and size of the pool tube. Henceforth, Avogadro’s law can be applied to inflate or deflate the given pool tube as per our necessity.
Avogadro's Number
Avogadro’s number is defined as the number of molecules of gas present in one mole that is huge (6.02×1023).
The unit for Avogadro number is mole-1.
Avogadro’s number is generally symbolized by N.
Avogadro’s number is a unit used by chemists for easy calculations all over the world.
Significance of Avogadro’s Law
After realizing that the volume of a gas is directly proportional the number of particles present in the gaseous molecules, this formula established a vital relationship for simple molecules at that time when the distinction between atoms and molecules was not visibly understood.
Specifically, the existence of diatomic molecules such as that H2, O2 and Cl2 was not identified until the results of researches involving the volume of gas molecules was discovered.
Limitations of Avogadro’s Law
This law is also known as Avogadro’s principle or Avogadro’s hypothesis. This law is only relevant to ideal gases and gives an estimated result for the real gases.
The gases with light molecules for instance helium, hydrogen, etc., follow Avogadro’s law more precisely as compared to the gases with heavy molecules.
Avogadro's Law Citations
- AVOGADRO’S LAW AND THE ABSORPTION OF WATER BY ANIMAL TISSUES IN CRYSTALLOID AND COLLOID SOLUTIONS. Science . 1913 Mar 21;37(951):427-39.
- Avogadro’s Hypothesis (or Law). Nature volume 82, page338 (1910)
- AVOGADRO’S LAW AND THE ABSORPTION OF WATER BY ANIMAL TISSUES IN CRYSTALLOID AND COLLOID SOLUTIONS. Science 21 Mar 1913: Vol. 37, Issue 951, pp. 427-439
Share
Similar Post:
-
Transport in Plants: Definition, Mechanism, and Types
Continue ReadingTransport in Plants: Introduction
Plants – Sessile, well developed tissue level grade of organization are the primary food producers for all the living organisms with least exceptions.
The energy of the sun and our waste respiratory product CO2 along with water becomes essential to produce sugars and other nutrient; vitamins and minerals which are obtained from the soil in which the plants are stationed to produce energy to plant dependent organism.
For a sessile organism to survive plants has developed many mechanisms to attain the basic needs for survival.
Tissue level organization is primitive even in higher plants with simpler but efficient structure to transport nutrients and water to the plants.
Uptake of nutrients and water is the key role in plant’s physiological process involving energy and carbon assimilation to produce Oxygen as a product.
Transportation in plants becomes essential and significant role in their physiological functions for the sedentary mode of life time employing simpler and number of techniques in combination to take nutrients from soil and water.
Specialized network of tissues connects the plants from its origin aids in nutrients translocation and distribution.
The specialized tissues are segregated and are present in all parts of body forming a connection between the nutrient receptor, storage, and synthesis regions of plants distinctly.
Major transportation in plants are water, minerals, and nutrients; distinctive pathway is defined for every transportable element; water and minerals are transported through XYLEM; Phloem another tissue transports and distributes organic matter to the sites of synthesis and their end products from synthesis site are distributed to energy utilizing site either as ATP or other sugar compounds.
Transportation in broader sense involves xylem and phloem – the vascular tissues provide a network to transfer the nutrients from source to the receiver site involves physics and chemistry to move evenly to sustain the plant.
Narrowing down; the cells also play a significant role in transportation and in energy utilization and storage.
Transport in cells plays a key role in the dynamics of cell were each cell functioning as a single unit integrates with neighbor’s cell wall and cell in integrating the flow of nutrient throughout the plant.
Transport in plant is extensively studied in earlier times by many scientists who experimented and identified the network of transporters laid out many theories for the transportation in plants and in trees.
History of Transport in Plants
The study of plant transport started back in 18th century by many scientists to understand the internal structure, circulation, and mechanical support for the plants.
It was an intriguing question on how a plant transports soil nutrients and water to the apex of the shoot and how does they synthesis their food?
Observing circulation in animals’ circulation in plants were also researched to understand the mechanism behind.
In earlier, 18th and 19th centaury many scientists observed various transport in plants by dissection and other methods and formulated theories of transportation of water and other elements.
The theory “Cohesion – Adhesion” developed by H. H. Dixon gave an acceptable mechanism in transport of materials in a general term of “Ascent of Sap”.
Transport in Plants Theories
Many theories have been put forward to understand the transport of water and other materials combinedly called as sap from the root to tip of the plant or a tree – Ascent of Sap. The theories were classified into three topics based on the ideology.
They are grouped into: 3 theories namely vital force; root pressure; physical force theories.
I. Vital Force Theory
The theory defines the movement of water or sap from root to other parts by the pulse created by the cortical cells which absorbs water from the outer side and pump them to the openings of xylem vessels.
The theory was put forth by J. C. Bose in 1923 also called a pulsation theory.
The theory stated that the cortical cells to be main cells to pump the water from the soil; which is proven wrong by eliminating roots from plant and the plant; stem in specific; still absorbed water.
II. Root Pressure Theory
The theory defines the movement of water or sap from root to other parts by the pulse created by the cortical cells which absorbs water from the outer side and pump them to the openings of xylem vessels.
The theory was put forth by J. C. Bose in 1923 also called a pulsation theory.
The theory stated that the cortical cells to be main cells to pump the water from the soil; which is proven wrong by eliminating roots from plant and the plant; stem in specific; still absorbed water.
III. Passive or Physical Force Theories
Theories corresponding to passive forces such as capillary force, collision force, atmospheric pressure, imbibition, diffusion pressure are factors upon which these theories are built upon.
Numerous scientists over a period have produced theories for identifying the transport.
They are:
a) Capillary Theory, 1863 by Boehm
Capillary movement is transport of substance over a small surface area over a small distance is acted upon by a small capillary force sufficient to pull water to a small extent.
Concept of capillary theory is based on the small force created by a narrow surface area to move a small amount of water.
The force is passive based on the physical properties of pressure and force and does not cost any energy.
Plant vascular system consists of tracheid and trachea which are longitudinal tubes of vascular bundles which when empty builds a force against gravitational force to pull the water from the roots and transport it to stem.
But this force is not sufficient to move to water column to the entire length of the plant.
b) Imbibition Theory, 1868 by Unger
Imbibition absorbs water on contact with water; swells by the pressure built up in a packed wood increase in surface area.
The pressure and increase in surface area pull the water but the force built up is exceedingly small to water to ascend the apex.
c) Cohesion - Tension Theory, 1894 by Dixon and Jolly
This is also called as Cohesion – Tension Transpiration Pull Theory.
The cohesive force and Transpiration pull combines to attract the water and other elements to move through the column of vascular tissues are now moved to the apex of the plant.
The cohesive force between the walls of xylem and hydrophilic water molecules attracts the molecules to the xylem wall.
Alongside xylem cohesive pull; water transpires when stomata open; which attracts water from nearby cells causing a Diffusion Pressure Deficit gradient between the guard cells and surrounding cells which causes diffusion from water filled cells to water deficit cells.
This theory was widely accepted by the scientific community thereby resolving a question of how a plant conducts water along its length.
Vascular Tissues of Transportation
Vascular tissues comprising xylem and phloem provides mechanical strength and support the plant in its sedentary lifestyle by transporting and distributing the assimilates from the site of synthesis to other parts.
The primary and secondary growth provides development of the vascular tissues to support even larger plants like trees where they reach a greater height.
The basic mechanism in transport is same in all organisms but distributing the synthesis and the network differs from species to species.
Phloem transports organic substance and nutrients from synthesis site and then to other storage sites and assimilation sites with network of vascular bundles which are well differentiated into various components such as fibers and other storage parenchymal cells.
Xylem and Phloem which are present in vascular bundles has many components.
Phloem comprised sieve tubes, companion cells, parenchymal cells, and fibers; transport organic substances for energy synthesis.
Xylem costs of tracheid’s, vessels, parenchyma, and fibers responsible for water and mineral uptake.
Transportion Classification
Transport in plants is classified to short distance transportation and long-distance transportation.
Short Distance Transport
The plants transport nutrients or water over a small distance.
Example: Water from soil is taken up by root hairs present in the soil by the process of diffusion where the root hairs are rich in solutes and when water is high in the soil; the difference in the concentration between root and exerts a pull for water from soil to the root hairs. The water then travels through the cells enter xylem.
Long Distance Transport
The plants and the organizing tissues transports water and nutrients to longer distance.
For Example: Water entering root xylem by diffusion is carried to the shoot apex of the plant by combined efforts of the diffusion, imbibition, transpiration, cohesion, and adhesion. Transpiration is the determining factor directly proportional to uptake of water.
Mechanism of Transportion
Mechanism of transport in plants as classified are of 2 main vascular bundles which transports water, minerals and other organic compounds by xylem and phloem, respectively.
Phloem transports organic compounds such as Sucrose and other carbohydrates from the region of synthesis; distributed to other plant parts of requirement to store or to be utilized in the process of energy production for growth and development.
For Example: Carbohydrates; sucrose synthesized in Leaves of plants; rich in chloroplasts and stomata assimilates CO2 and converts into carbohydrates (Sucrose) carried again through phloem to other parts of the plants such as stem, flower and to developing shoots through network of vascular bundles connecting plant parts.
The phloem vessels and cells present from the root hair to the apex facilitates the assimilate transport from the synthesis point to other regions of plant.
Phloem transports organic materials by a mechanism of mass flow of substance through circulation.
Similarly; Xylem transports water and minerals from roots to the apex of the plants through various mechanisms in combination with Cohesive and Transpiration to other parts of plant.
Xylem transports water and minerals unidirectionally; varies from phloem circulating the metabolic products bidirectionally (i.e.) Root to Apex, Leaves; Leaves to Stem, flower, root.
Water is taken from the soil through root hairs through the process of osmosis; from roots the water is further taken up by the combined action of Transpiration, Capillary Action, and root pressure.
Changes in any one factor has a respective contribution and determining role in uptake of nutrients.
Minerals are also taken up by xylem by a different action of Diffusion; uptake of nutrients passively by the difference between the concentration gradient; and Active Transport utilize ATP, an energy molecule to move a molecule using transmembrane protein from extracellular matrix to the cell’s internal environment to mediate many metabolic processes.
Each mechanism and processes have its significant role in uptake of nutrients and act as a limiting factor in controlling the transport.
Transport in Plants Citations
- Molecular mechanisms of boron transport in plants: involvement of Arabidopsis NIP5;1 and NIP6;1. Adv Exp Med Biol . 2010;679:83-96.
- Molecular mechanisms of urea transport in plants. J Membr Biol . 2006;212(2):83-91.
- Strategies for optimization of mineral nutrient transport in plants: multilevel regulation of nutrient-dependent dynamics of root architecture and transporter activity. Plant Cell Physiol . 2014 Dec;55(12):2027-36.
Share
Similar Post:
-
Mitosis vs Meiosis: Chart, Definition, and Diagram
Continue ReadingMitosis vs Meiosis: Introduction
Both are type of cell division taking place in every eukaryote. But the main difference is Mitosis produces Diploid Somatic cells identical to parent and Meiosis give rise to cells which forms a new progeny which are genetically different from the parent by producing haploid gametes.
The differences vary mitosis from meiosis producing regular somatic cell and differentiated gametes of future progeny respectively.
Out of 2 cellular divisions in meiosis; Meiosis II is more similar to mitosis with the difference in the end products of haploid gametes and regular diploid somatic cells respectively.
Mitosis vs Meiosis
Mitosis Meiosis Two daughter cells are produced from a single cell Four daughter cells are produced from a single cell Chromosomal segregation separates equal number of chromosomes to the progeny Chromosomal segregation separates only half chromosomes of the single cell Infinite cell cycle rotation varies in different cells Single rotational cell cycle A cell cycle involves 2 Gap phases and one synthesis and Mitotic phase Cell cycle involves 2 continuous Meiosis preceded by single gap phase and synthesis phase No homologous chromosomes are found Homologous chromosomes are attached during Prophase Recombination is not required as the division involves a replication of unmodified genetic material Recombination is the main specialty of meiosis where the genetic material is non – sister chromatids are exchanged with each other Daughter cells are identical to parent Daughter cells are varied from the parent During development the division produces number of differentiated cell lineage based on the location, hormone regulation etc., During division it produces single lineage of cells Chromosome divides during Anaphase Chromosomal division is during Anaphase II The cells can be Haploid or Diploid The cells undergoing such division contains only diploid number of chromosomes and above Cells which undergo such division are called as Somatic cells Such division gives rise to sex cells called Gametes Mitosis vs Meiosis Diagram
I. Mitosis Diagram
II. Meiosis in Oocyte
III. Meiosis in Sperm
Why We Need Meiosis?
o Eukaryotes are evolved and well distinguished for the various adaptive features to survive the dynamic changes and evolved along the changes.
o Changes in the environment was followed by the adaptation in organism for the respective environment was motivated by an act of survival and to ensure a progeny to develop the lineage thereby sustaining life on earth.
o Environmental modification led changes in animals and plants; regulated the diversification and population growth of all organism by frequent modifications in niche where the organism functions to its fullest; challenging the organisms to promote change in functionalities for the survival factor.
o Charles Darwin pointed out the Theory of “Natural Selection” where the organisms are naturally and randomly selected by nature to develop lineage.
o He called it the ” Survival of Fittest” where the organisms suitable for the environment survived and others which couldn’t survive became extinct.
o The Survivors became the key organism for the variability among the genus, species level which on further adaptions evolved to give rise to new classes and phyla.
o Changes governing evolution are inherited from parent to offspring; is sexually selected – another phenomenon of evolution and diversification; mediated by special type of cell division Meiosis.
o Gametes of meiosis inherits the changes from parent during fertilization to produce competitive offspring for better survival and variability from parents by giving it a unique identification and distinction from the parent.
o Differentiation, compatibility to the environment is genetically marked and inscribed in the genes from parents separately before the fertilization.
o The inheritance of the qualities is determined post fertilization in zygote involves principles of genetics while exhibiting features of an organism.
o Such unique, distinctive characteristics of an organism predetermined in gametes of parents; formed by a reductive division.
o Meiosis revolves around the components of cell cycle and molecular activation by an organism.
o The cell of meiosis initially are a result of mitosis and meiosis is the smallest but significant part in life history of any organism.
o The specialized division becomes more significant for its role in determining the characteristics of future progeny and aids in variability which on long run evolves the organism.
o Meiotic steps are crucial in determining half feature of an organism by each parent to make up the whole organism.
Significance of Meiosis
1. Evolution of sexual reproduction in eukaryotes are marked by Meiosis. Sexual reproduction becomes and important characteristic feature of meiotic division; involves maternal gametes and paternal gametes to determine the ability of an organism.
Sexual reproduction involves fertilization between same species with distinct genetic characters originated from their unrelated immediate ancestors to produce viable gametes to compete and accustomate to the environmental challenges for survival.
2. Meiosis is conserved in broader terms among all sexually reproducing eukaryotes. Broadly, the mechanism of meiosis is similar in all eukaryotes involving same steps and function.
Changes from the preset is that each organism takes different time to proceed the cycle of meiosis and end products can be different from each species in structure and function.
3. Meiosis maintains a constant chromosome number. Advantage of using meiosis over mitosis for gamete production is to maintain the chromosome number.
On mitotic division; the chromosomes produce daughter cells with diploid chromosome number; if the same prevails; for meiosis the chromosomes double on each fertilization resulting in doubling at each generation.
For example: 2n –> 4n –> 8n –> 16n…….. infinity.
4. Recombination of paternal and maternal chromosomes produces genetic variability, diversity and in turn evolution.
Recombination is a process of exchange of genetic material between maternal and paternal chromosomes with the progeny to get a combination of both traits and not either of the traits causing reduced viability in offspring.
Crossing over is a step-in prophase where the homologous chromosomes pairs by a synaptonemal complex and crosses each other in further steps by a chiasma; providing a bridge for the exchange of the genetic material.
5. Recombination takes place with rules and by the process of law of independent assortment. The law stated by Mendel says that the genetic material of maternal or paternal chromosomes are independently crossed over to recombine with each other to produce variabilities in the haploid gametes to express traits of both maternal and paternal in origin.
6. Positive adaptation caused by mutation suitable for the environment is naturally selected and carried over to next generation. Meiosis is the process of random selection and fusion of male and female gametes to future generation.
Any changes in the germ cell chromosomes are inherited to the next generation and are exposed to the environment; surviving with the mutation in ease might take the changes to generations further and undesirable change caused by mutation might be eliminated rapidly because of the in functionality of the process.
7. The segregation, crossing over and recombination of the chromosomal components ensures the variable inheritance of parental chromosomes. The recombination produces diversity among the population on long run produces variability and then evolve to new organism or to any environment.
8. After the meiosis the post – miotic process or the end product might vary from species to species. Plants after meiosis produces 4 microspores in anthers and 4 megaspores in Female. The microspores 3 degenerates one fuse with one megaspore.
Later, the remaining haploid megaspores combine to form endosperm in one stage to provide a developmental part of other fusion.
Mitosis vs Meiosis Citations
- Recombination, Pairing, and Synapsis of Homologs during Meiosis. Cold Spring Harb Perspect Biol . 2015 May 18;7(6):a016626.
- Meiosis: the chromosomal foundation of reproduction. Biol Reprod . 2018 Jul 1;99(1):112-126.
- Abnormal mitosis in reactive astrocytes. Acta Neuropathol Commun . 2020 Apr 15;8(1):47.
- Mitosis in vertebrates: the G2/M and M/A transitions and their associated checkpoints. Chromosome Res . 2011 Apr;19(3):291-306.
Share
Similar Post:
-
Meiosis II: Definition, Stages, Phases, and Diagram
Continue ReadingMeiosis II: Introduction
o The living world has seen many numbers of generations and successions of organism evolved adaptively to the pertaining environmental changes; sustaining the diverse lifeforms on The Earth.
o Sustenance of a species and its lineage is the cumulative adaptations of the ancestors inherited over a million years to reach the present morpho – functional form of beingness.
o The inherited changes from parent to offspring, its proliferation supported by external growth factors and the environment; developed the organism to become fit and ensure viability for further generations to sustain.
o The fundamental cellular process supporting the growth and development is the inheritance of expressive genes from the parents to offspring mediated by the process of Meiosis.
o Cell division that leads to the contribution of one half of the chromosomes from each of the sexually reproducing parent to offspring is meiosis.
o Sexual reproduction is possible among the same species with same number of chromosomes and are equally contributed to the offspring so that half of maternal and paternal genes are contributed to the progeny.
o Meiosis is specialized because of the variability it provides to the offspring by the recombination of the homologous genetic material and the production of reduced chromosome where a diploid cell gives haploid daughter; on fusion of the male gamete (Sperm in animals and pollen in plants) and female gametes Eggs (plants and animals) produces diploid zygote proceeds with mitosis to develop into new organism.
Mechanism of Meiosis II
o Significance of meiosis is that it takes place twice to segregate the homologous pair and give 4 haploid cells in continuous division without any gap between the two division.
o At the end of Meiosis I, the single gamete on induction becomes divided into 2 diploid cells with varied genetic expression due to the recombination enter the meiosis II.
Meiosis Diagram in Sperm
o Meiosis II is a replica of Mitosis with a difference in chromosomal composition of the somatic cells and the meiotic cell.
o The Meiosis I and Meiosis II has no gap phase between them to duplicate the 46 chromosomes present in the cell at the end of the Telophase I.
o Other components are similar to that of mitosis; wherein prophase II has the same rule where the chromatin condenses faster to become a chromosome.
o Metaphase II includes the appearance of the spindle fibers from the organizing center attaches to the sister kinetochores of the same chromosomes; a difference from the METAPHASE I where one of the sister chromatids of the homologous are attached.
Meiosis Diagram in Oocytes
o The chromosomes are attached to opposite end fibers of the other sister kinetochores and aligns in the center of the cell forming equatorial plate.
o This phase has a regulator where all the chromosomes must be attached at the sister kinetochores of the opposite poles to initiate Anaphase where the real separation of haploid chromosomes takes place.
o At Anaphase II the sister chromosomes held by cohesins are removed by the cascade activity of separase; chromosomes when bound induces APC/C complex which eliminates the repressor of separase and separase on removal of repressor cleaves cohesins along the length of the sister chromatids including centromere.
o Cohesin degradation releases the tension maintained when held at the equator which pulls the chromatids to opposite ends separating the haploids to the opposite ends.
o Reaching poles, the last Meiosis II stage starts by forming a deep furrow between cells and formation of cell organelles and nuclear membrane and separates.
o Post Meiotic II involves maturation of the germ cells and re – organization of the structural and functional capability of the cell.
o In female, the cell matures to eggs and in male the cells undergo structural modification to attain a sperm with head, neck and tail and the transformation varies for different groups of eukaryotes.
Meiosis II Citations
- Polo is not solo in meiosis. Cell Cycle . 2018;17(3):273-274.
- The histone codes for meiosis. Reproduction . 2017 Sep;154(3):R65-R79.
- Cell Cycle-specific Measurement of γH2AX and Apoptosis After Genotoxic Stress by Flow Cytometry. J Vis Exp . 2019 Sep 1;(151).
- Flow Cytometry Analysis of Cell Cycle and Specific Cell Synchronization with Butyrate. Methods Mol Biol . 2017;1524:149-159.
- Novel insights into cell cycle regulation of cell fate determination. J Zhejiang Univ Sci B . 2019 Jun;20(6):467-475.
- Cell Cycle-Dependent Control and Roles of DNA Topoisomerase II. Genes (Basel) . 2019 Oct 30;10(11):859.
Share
Similar Post:
