Tag: Hydrogen

Introduction

The widely recognized nebular theory postulated that a massive cloud of dust including hydrogen and other gases created the solar system, including the planet earth. Small earthly particles like iron and nickel were created as a result of the earth’s contraction, rotation, and lowering of temperatures. The planet was created approximately 4.5 billion years ago after millions of years of precipitation and accumulation. Since then, the earth’s temperature has decreased, causing the crust to become more fragile. However, the earth’s interior core is still hot and igneous.

A short note on Prehistoric Earth’s Origin of Life

There were numerous theories about the origins of life on Earth. 

• According to the Panspermia theory, some scientists thought life originated from spores that came from outer space, while others hypothesized that it originated from decomposing materials like dirt, straw, etc (Spontaneous generation theory). Different experiments were carried out by various scientists, and they all disproved the hypothesis of spontaneous generation. 
• Later in 1953, Oparin and Haldane advanced the theory that life emerged from pre-existing non-living organic molecules like RNA, DNA, and other similar molecules because of abiotic chemical reactions.
• Numerous studies have suggested that RNA came before DNA, even though it is still unclear what replicating molecule was the earliest. Because RNA molecules can self-replicate and are simpler than DNA, they are considered autocatalytic.

Precambrian Life

The Precambrian period includes the Archean and the Proterozoic eons from 4.6 billion years to 542 million years. Most of the life that existed during the Precambrian period were prokaryotic organisms. Microfossils that looked like stromatolites and cyanobacteria from the Precambrian epoch first revealed the presence of life about 3.8 billion years ago (layered mounds). Additionally, the absence of oxygen in the early atmosphere rendered primitive organisms anaerobic. However, when cyanobacteria developed photosynthesis, it added oxygen to the atmosphere.

Eukaryotes, which have a nucleus, cytoskeleton, organelles, and mitotic spindle, first evolved around two billion years ago. It was once thought that endosymbionts like mitochondria and chloroplasts descended from bacteria. The evolution of eukaryotes benefited greatly from these endosymbiotic relationships.

Cambrian Explosion- Origin of Animal Diversity

The surge in the diversity of multicellular organisms during the early Cambrian epoch, which began 540 million years ago, is known as the Cambrian explosion. Tens of millions of years before the early Cambrian epoch, the first multicellular living forms began to appear as fossils. These ancient animals have diverse body designs from those of living creatures today. They vanished and were replaced by modern-day animal body types in the Cambrian fauna.

Evolution of Land Plants

The evolution of land plants from a green algal ancestor is a significant event in the history of life since it caused profound changes in the earth’s environment and the formation of the entire terrestrial ecosystem. The formation of land plants and the divergence of the four main surviving clades (liverworts, hornworts, mosses, and vascular plants) may have taken place during the late Ordovician and Silurian periods, according to evidence from fossil spores found in the mid-Ordovician.

Formation 

The majority of researchers concluded that the earliest life form and subsequent other life forms on earth appeared as a result of chemical evolution, or the production of molecules. The Nebular theory, developed by Immanuel Kant and Pierre Laplace, postulates that planets are formed by a cloud of hydrogen and helium. Clouds were created by tiny particle collisions, and the planet itself was created through accretion.

Evolutionary Milestones

• Life’s history is represented by several milestones. For instance, unicellular organisms first appeared on Earth, and ever since then, diversification has led to the emergence of complex living forms. These living forms will eventually go extinct and be replaced by other creatures. 
• Complex living forms evolve as a result of this evolution. According to some fossil research, numerous species began to independently become multicellular around 1 billion years ago, and animals started to grow hard portions in their bodies to survive on the earth. 
• Dinosaurs were the most prevalent class of creatures on the planet for millions of years. For a considerable amount of time, they dominated the prehistoric landscape before a disaster led to the extinction of dinosaurs.
• The Great Apes, from which humans emerged, was the next significant event. Human evolution is still clearly visible, although it has not yet reached its conclusion.

Presence of Humans

• The most well-known species, Homo sapiens, is a descendant of hominids, the first creatures that resembled humans. 
• According to several fossil records, archaeological findings, and embryological research hominids are thought to have diverged from other primate species in the southern and eastern African areas 2.5–4 million years ago. 
• As a result, they have bipedalism in common (the ability to walk on two legs).
• Additionally, as hominids evolved and adapted to their habitats, their brain sizes grew. Around 2.3 million years ago, Homo habilis, the earliest human-like hominid, had a brain size of 650–800 cc and started using stone tools.
• Fossils discovered in Java in 1891 revealed the existence of Homo erectus, the next stage of human evolution, some 1.5 million years ago. They have a 900cc larger brain due to evolution. Then they began to migrate from Africa to Eurasia, where they started to learn how to make fire and develop defenses.

Summary

The widely recognized Nebular Theory postulated that a massive cloud of dust, including hydrogen and other gases, created the solar system, including the planet Earth. The majority of scholars concluded that the earliest life form and subsequent other life forms on earth appeared as a result of chemical evolution, or the production of molecules. Dinosaurs were the most prevalent class of creatures on the planet for millions of years. The most well-known species, Homo sapiens, is a descendant of hominids, the first creatures that resembled humans.

Frequently Asked Questions  

1.What is Coal’s Formation Process? List the Types of Coal.
Ans. The layers of dead plants and animals underwent physical and chemical changes as a result of pressure and heat. Deposits rich in carbon were created as a result of this. Different forms of coal include lignite, bituminous coal, and anthracite.

2.Explain Index Fossils?

Ans. Index fossils are fossils that are used to identify geologic formations with broad regional distributions and short time scales. These fossils are numerous, dispersed, limited in geological time, and unique.

3.What Factors led to the Earth’s Changes?
Ans. Physical changes such as mountain development, tectonic movements, volcanic eruptions, climate changes, and biological changes on the planet resulted from the evolution of new life forms.

4.What are the Necessary conditions for Life to Sustain on Earth?
Ans. The necessary conditions for life to sustain on earth are as follows,

• Proper distance from the sun
• Presence of water and the atmosphere
• Existence of the lithosphere and biosphere
• Ideal temperature ranges (around 17 degrees Celsius).

Introduction

Pressure can be defined as the force exerted perpendicularly per square unit of area of any object. It is represented by the formula,                                                                                                                        

                                                             P = F ⁄ A

where P is the pressure, F is the force exerted on the object, and A is the area of the object. Pressure is measured in pascal, and is classified into absolute, atmospheric, differential, and gauge pressure. A change in pressure has different effects on different states of matter.

Change in Pressure

Since the pressure exerted on an object is the amount of force applied per unit area of that object, a change in area or a change in the amount of exerted force can result in a change in pressure. For example, if the surface area decreases, the pressure increases simultaneously when the surface area decreases, the pressure decreases provided that the force applied remains constant. 

Effect of Pressure on the States of Matter

Pressure change can have different effects on different states of matter. By exerting pressure on the matter particles, we can draw them closer. Therefore, applying pressure can cause liquids to turn into solids, and when pressure is applied to a gas that is contained in a cylinder, the gas begins to compress and turn into a liquid. As pressure rises, the volume of the gas reduces, which causes the gas to change into a liquid and then finally a solid. The volume of a gas is inversely related to its pressure and directly relates to the number of molecules it contains.

Pressure has less of an impact on solids because they are non-compressible forms of matter. By applying pressure and lowering the temperature, liquids can be transformed into solids.

Effect of Pressure on Equilibrium

The equilibrium will adjust to minimize a change in the pressure of a gaseous reaction mixture. If the pressure is raised, the equilibrium will change to favour a fall in the pressure. The equilibrium will change if the pressure is reduced to favour an increase.

When a system’s volume is reduced, the pressure will rise (and the temperature is constant). A greater number of collisions occur with the container’s walls. There will be fewer collisions and hence less pressure if there are fewer gas molecules. The equilibrium will change in a way that reduces the number of gas molecules, which will likewise reduce the pressure. To forecast which way equilibrium will shift in response to a change in pressure, we must consider how many gas molecules are involved in the balanced reactions.

For example, the chemical reaction between nitrogen and hydrogen is shown below:

                                                           N2 (g) + 3H2 (g)→ 2NH3↑

The proportion in the equation that balances is 1:3:2. In other words, the 1N2 molecule combines with the 3H2 molecule to produce NH3 gas (from the balanced equation). Four molecules of reactant gas must therefore be present to produce two molecules of product gas.

• Pressure buildup will favour the reaction which results in fewer gas molecules. Because there are fewer product gas’ molecules, the forward reaction is more advantageous. Due to the rightward shift in equilibrium, the yield of NH3 will rise.
• The reaction that produces more gas molecules will be more favourable as pressure drops. If there are more reactant gas molecules present, the reverse reaction is more favourable. As a result of the equilibrium shifting to the left, the yield of NH3 will decline.

Some Facts

• Pressure is directly proportional to the temperature.
• In contrast to solids and liquids, gases are more easily subjected to pressure.
• Compared to gases, solids and liquids are less sensitive to pressure.
• When air pressure is raised, the boiling point of water rises.
• The equilibrium will adjust to minimize the change in pressure of the gaseous mixture.

Frequently Asked Questions

1. Does Changing the Size of the Container Affect the Pressure?

Ans: No change in concentration could change the pressure if the equilibrium reaction does not involve a change in the number of molecules in the gas phase. Therefore, altering the container’s size without also altering the pressure would have no impact on the reaction. The number of molecules stays constant and applies the same pressure whether the container size decreases or grows.

2. How can the Physical Condition of the Matter be Altered?

Ans: It is also possible to change the physical state of matter by adjusting the pressure that is applied. For example, by applying pressure and lowering the temperature, gases can liquefy. 

3. How does Pressure Affect the Boiling Point of a Liquid?

Ans: All liquids evaporate with an expansion. The expansion and delay of vaporization are the results of pressure on the surface. As a result, when pressure is applied, the boiling point rises.