Lavoiser’s Law
Let’s imagine, if we want to make bread we will mix wheat and bread flour. Example, we will add 1 kg of wheat flour with ½ bread flavor. So, the mixed will result 1 ½ kg mass.
From the ilustration above we can applied in Lavoiser law with his postulat . That is The Law of Conservation of Mass (or Matter) in a chemical reaction can be stated thus:
“In a chemical reaction, matter is neither created nor destroyed. “
“mass before equals mass after”
It was discovered by Antoine Laurent Lavoisier (1743-94) about 1785. However, philosophical speculation and even some quantitative experimentation preceeded him. In addition, he was certainly not the first to accept this law as true or to teach it, but he is credited as its discoverer.
Antoine-Laurent de Lavoisier (26 August 1743 – 8 May 1794);), the "father of modern chemistry"was a French nobleman prominent in the histories of chemistry and biology. He stated the first version of the law of conservation of mass,[2] recognized and named oxygen (1778) and hydrogen (1783), abolished the phlogiston theory, helped construct the metric system, wrote the first extensive list of elements, and helped to reform chemical nomenclature. He discovered that, although matter may change its form or shape, its mass always remains the same.
Lavoisier is now known as the Father of Modern Chemistry. However, when Lavoisier started his experiments on combustion and respiration, chemistry was still in the very early stages of development. There was lots of empirical information but very little theoretical basis and no formal language. Enough characteristics of acids, alkalis, salts and metals were known so that they could usually be distinguished, but gases were hardly known to exist. Lavoisier was an excellent discoverer because he was quick to see the significance of new findings. He readily confirmed and extended the experimental discoveries of others and formed mental models to organize all of these ideas. He was one of the few chemists at the time to fully appreciate the importance of careful measurements of reactants and products. In order to make such careful measurements he invented a balance which was good to about .0005 grams. He proved the Law of Conservation of
Mass, showing that the mass of the reactants had to equal the mass of the products.
In daily life, do you know why wood can be burn or iron can be rust? That is because there are oxidation processes. This is called Phlogiston theory. Phlogiston theory was a 17th century attempt to explain oxidation processes such as fire and rust. Still, phlogiston remained the dominant theory until Antoine-Laurent Lavoisier showed that combustion requires a gas that has weight (oxygen) and could be measured by means of weighing closed vessels. The use of closed vessels also negated the buoyancy which had disguised the weight of the gases of combustion. These observations solved the weight paradox and set the stage for the new caloric theory of combustion.
During the eighteenth century, as it became clear that metals gained weight when they were oxidized, phlogiston was increasingly regarded as a principle rather than a material substance.By the end of the eighteenth century, for the few chemists who still used the term phlogiston, the concept was linked to hydrogen. Joseph Priestley, for example, in referring to the reaction of steam on iron, whilst fully acknowledging that the iron gains weight as it grabs oxygen to form a calx, iron oxide, iron also loses “the basis of inflammable air (hydrogen), and this is the substance or principle, to which we give the name phlogiston.”Following Lavoisier’s description of oxygen as the oxidizing principle (hence the name oxygen: oxus = sharp, acid; geneo = I beget), Priestley described phlogiston as the alkaline principle.
In some respects, the phlogiston theory can be seen as the opposite of the modern "oxygen theory". The phlogiston theory states that all flammable materials contain phlogiston that is liberated in burning, leaving the "dephlogisticated" substance in its "true" calx form. In the modern theory, on the other hand, flammable materials (and unrusted metals) are "deoxygenated" when in their pure form and become oxygenated when burned. However, the first part of the old theory requires that phlogiston has weight (since ashes weigh less), but the second requires that it have no weight or negative weight, since corroded metals weigh the same or more, depending on whether or not they are allowed to corrode in sealed chambers.
Oil burning, an application of the laws of conservation of mass .Oil burning, an application of: - Lavoisier's law of conservation of mass / matter (1789) which states that the mass of a closed system of substances will remain constant, regardless of the processes acting inside the system. An equivalent statement is that matter changes form, but cannot be created nor destroyed. This implies that for any chemical process in a closed system, the mass of the reactants must equal the mass of the products. and - The first law of thermodynamics (conservation of energy) which states that the increase in the internal energy of a system is equal to the amount of energy added by heating the system, minus the amount lost as a result of the work done by the system on its surroundings. In other words: energy can be transformed (changed from one form to another), but it can neither be created nor destroyed. The same amount of mass / matter / energy (from the Sun, the atmosphere, and Earth) needed to grow the life to produce the oil was released when it burned.
Highly concentrated sources of oxygen promote rapid combustion. Fire and explosion hazards exist when concentrated oxidants and fuels are brought into close proximity; however, an ignition event, such as heat or a spark, is needed to trigger combustion. Oxygen itself is not the fuel, but the oxidant. Combustion hazards also apply to compounds of oxygen with a high oxidative potential, such as peroxides, chlorates, nitrates, perchlorates, and dichromates because they can donate oxygen to a fire.
Concentrated O2 will allow combustion to proceed rapidly and energetically.Steel pipes and storage vessels used to store and transmit both gaseous and liquid oxygen will act as a fuel; and therefore the design and manufacture of O2 systems requires special training to ensure that ignition sources are minimized. The fire that killed the Apollo 1 crew in a launch pad test spread so rapidly because the capsule was pressurized with pure O2 but at slightly more than atmospheric pressure, instead of the 1⁄3 normal pressure that would be used in a mission.
Liquid oxygen spills, if allowed to soak into organic matter, such as wood, petrochemicals, and asphalt can cause these materials to detonate unpredictably on subsequent mechanical impact. As with other cryogenic liquids, on contact with the human body it can cause burns to the skin and the eyes.
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