Introduction
The matter is the amount of substance. There are three states of matter: solid, liquid, and gaseous states. These states of matter are traditionally distinguished by the arrangement and proximity of their particles or molecules. In a solid state, the substance particles are closely packed, compact with strong interactive bonds between them, and have a definite shape. They also exhibit high melting and boiling points. Liquid molecules are more spaced but are still held together by weak forces. Liquids have no definite shape and have relatively low melting and boiling points. Gases on the other hand have disorderly particles that are widely spaced with very weak forces between them
The gaseous state
Ideal Gas Concept
An ideal gas is a theoretical model of the behavior of molecules. The ideal gas concept is important because it allows for easier analysis of gases as it obeys the ideal gas law.
At standard temperature and pressure, real gases behave relatively like ideal gas. An increase in temperature with a subsequent decrease in density, however, increases deviation from the ideal gas behavior. Physical quantities of real gases like pressure, volume, and mass can easily be measured. One of the quantities can then be kept constant as the rest are varied to find out the effect of these quantities on each other (Denniston, Topping & Caret 161 ).
Scientists Boyle, Charles, Avogadro, Dalton, and Gay-Lussac developed laws upon which these concepts can be investigated.
The Gas laws
The kinetic molecular theory
This theory describes an ideal gas as one in which there are no attractive or repulsive forces and in which the particles are presumed to have very small volumes that are thus neglected.
Boyle’s law
Boyle’s law states that at constant pressure and a fixed number of moles, the volume of gas then has an inverse relationship with the pressure it exertsi.e.
PV = k
(Denniston, Topping & Caret 163).
Setting Initial and final conditions as
PiVi = k1
PfVf = k1
Then,
PiVi = PfVf
Because k is a constant.The formula can then be rearranged and used to solve for the pressures and volumes. E.g. for the final volume:
Vf = PiVi / Pf
Charles’s law
Charles’s law states at constant pressure and fixed number of moles, then the volume of a gas has a direct relationship with the absolute temperature (Denniston, Topping & Caret 165).
The ratio of volume to time is a constant
V/ T = k2
Initial and final conditions can the be set as follows
Vi / Ti = k2
Vf / Tf = k2
Since k2 is constant, then the two equations can be equated to form
Vi / Ti = Vf / Tf
That equation can then be used to solve for the different volumes and pressures given initial or final conditions.
Avogadro’s law
Avogadro’s law states that at a constant temperature, equal volumes of any gas contain an equal number of moles.
i.e.
V/ n = k3
Relating initial and final conditions
Vi / ni = Vf / nf
The molar volume of a gas is described as the volume occupied by one mole of the gas. At 273 k (or 0°c) and 1 atm. pressure (standard temperature and pressure, stp), the volume of an ideal gas is 22.4l
The Ideal gas law
The ideal gas law is obtained by combining Boyle’s law, Charles’s law, and Avogadro’s law.
So that.
So that
PV = nRT
Where
R=the ideal gas constant
n=number of moles
T=absolute temperature measured in Kelvin
The combined gas law then gives a simple and convenient formula that is used to solve gas law problems involving pressure, volume, and temperature
The combined gas law equation is derived from Charles and Boyle’s laws and takes the form:
PiVi / Ti = PfVf / tf
It must be noted that the above laws and equations work on the assumption that the gases under observation are ideal gases. Standard conditions of temperature and pressure are also assumed: 0 °C (273.15 K, 32 °F) and a pressure of 1 atm.
Pressure, volume, and temperature observed using the gas laws are purely physical and not chemical properties hence the emphasis on standard conditions of temperature and pressure.
Dalton’s law
Dalton’s law states that “the total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture” (Houghton 1362).
Greenhouse gases
Greenhouse gases are atmospheric gases that take in radiation and emit it in the thermal infrared range leading to the greenhouse effect. Water vapor, carbon dioxide, methane, nitrous oxide, and ozone are the major greenhouse gases in the atmosphere. These gases have a great influence on the earth’s physical condition especially with respect to temperature. The greenhouse effect has slowly but surely led to an average increase in the earth’s temperature; a phenomenon referred to as global warming. This has led to a change in the climate and weather patterns on earth (Trenberth & Kiehl 200).
How much greenhouse effect a gas has depends on its characteristics and abundance. Methane is known to have a much larger effect per molecule than carbon dioxide for instance, but carbon dioxide exists in much larger quantities. On average then, carbon dioxide has a more greenhouse effect than methane despite the fact that methane’s effect per molecule is about 8 times that of carbon dioxide. (Houghton 1362). Water vapor and carbon dioxide are ranked as the top two contributors to the greenhouse effect with water vapor contributing 36-72 % while carbon dioxide contributes 9-26 % (Trenberth & Kiehl 198)
Air pollution
Air pollution is the phenomenon where foreign matter like particles, chemicals or biological materials that are harmful to any form of life or that can lead to a change in the natural environment is introduced to the atmosphere.
The main sources of air pollution are attributed to human activity. Sulfur, Nitrogen, and carbon oxides are the most notable pollutants. Sulfur dioxide oxidation in the presence of a catalyst leads to the formation of sulphuric acid which combines with rainwater to form acid rain. Acid rain is harmful to plants and aquatic life and leads to the death of fish and other aquatic life. Nitrogen Dioxide is a toxic reddish-brown gas with a sharp smell normally emitted from high-temperature combustion and is an air pollutant. Carbon monoxide on the other hand is a greenhouse gas that comes about due to incomplete combustion. It is particularly dangerous because it is odorless and non-irritating yet very poisonous.
Conclusion
The gas laws are very instrumental in the experiments and problems that relate to gases. They can be used in the design of air cleaning or conditioning systems and can be incorporated in researches that can yield ways and means of minimizing global air pollution.
Works cited
Denniston,Katherine, Topping, Joseph and Caret, Robert. General, Organic, and Biochemistry: Chemistry for Health Professionals 1 Sixth Edition. Medgar Evers College, New York :The McGraw-Hill Companies Inc, 2008.
Houghton, John.”Global warming”. Institute of Physics 2005.
Kiehl, Jeremy and Trenberth,Job “Earth’s Annual Global Mean Energy Budget”. Bulletin of the American Meteorological Society 78.2 (1997): 197–208.