NS003

• A mole is an SI unit for chemical quantity, denoted by the symbol "mol."
• A mole, by definition, is the number of particles in exactly 12 g of carbon- 12. One mole is equivalent to 6.02 x 1023 particles of a certain substance.
• Avogadro's number is only a representative number of all the particles in a substance.
• An equal number of moles would also mean an equal number of particles and vice versa. You can calculate how many actual particles are present in a given amount of moles by using p = n An
• The molar mass of a compound is called the molecular mass or the formula mass. It is equal to the sum of all the average atomic masses of all the atoms present in a compound.
• The empirical formula of a compound gives the lowest whole-number ratio of the atoms of the elements in the compound.
• A molecule is composed of two or more atoms. The air in the atmosphere, the water in the ocean, and the DNA in our bodies are all made up of molecules.
• The process by which particles move freely to fill up any available space is called diffusion.
• Gas molecules diffuse faster than liquid molecules. Solids do not diffuse at all.
• Gas density is usually measured in grams per liter (g/L).
• Kinetic Molecular Theory


  According to this theory, gases are made up of tiny particles that are always in random and straight-line motion. These particles move very fast and can only change direction when they collide with one another or with the walls of the container. There are more assumptions set by the kinetic molecular theory to explain different properties of gases.
• Gases are made up of tiny particles called molecules. These molecules are in constant, random, and straight-line motion. The molecules will continue in their straight-line motion until they collide with another molecule or with the walls of the container.
• The collisions of the molecules with one another or with the walls of the container give rise to the gas pressure. The particles and the wall of the container neither lose nor gain energy during these collisions. All collisions are perfectly elastic.
• The molecules are considered point particles. This means that the particles have mass but have very small to negligible volume. The size of the particles is very small compared with the separation distance between them.
• Gas molecules have no forces of attraction or repulsion between them.
• All gases at the same temperature have the same average kinetic energy. The average kinetic energy is directly proportional to the absolute or kelvin temperature of the gas.
• Gases do not have a definite shape or volume.
• The average kinetic energy of gas particles of a given amount of gas is directly proportional to its absolute temperature.
• The amount of gas pertains to the amount of particles present in a given sample.
• The kinetic molecular theory describes gas pressure as the cumulative force that all the gases particles exert as a result of their collision with one another or with the walls of the container. Pressure is simply the force exerted on a given with area.
• The pressure exerted by the atmosphere on anything on Earth's surface is called atmospheric pressure. Atmospheric pressure decreases with altitude the air density decreases with altitude. There will be less gas particles exerting pressure at higher altitudes compared at lower altitudes.
• The barometer is the instrument used to measure atmospheric pressure, was invented by Evangelista Torricelli. His barometer was composed of an inverted glass tube filled with mercury in a dish. At a standard pressure of 1 atmosphere (atm), mercury column will reach a height of 760 mm.
• Evangelista Torricelli invented this simple barometer which is used to measure atmospheric pressure.
• The standard unit for pressure is the pascal (Pa). For gases, the common units used to express pressure are atmosphere (atm), mm of Hg or torr, and cm of Hg. The term standard pressure refers to a pressure of 1 atm.
• Robert Boyle discovered the inverse relationship between volume and pressure at constant temperature.
• The quantitative relationship between the volume of a gas and the pressure of the gas at constant temperature is known as BOYLE’S LAW.
• Pressure is inversely proportional to Volume.
• JACQUE CHARLES stated that the Kelvin temperature and the volume of the gas are directly related when there is no change in pressure or amount of gas.
• Volume is directly proportional to Temperature in Kelvin.
• JOSEPH LOUIS GAY-LUSSAC stated that the pressure of a gas is directly related to its Kelvin temperature.
• The pressure exerted by a gas is directly related to the Kelvin temperature.
• Amadeo Avogadro hypothesized that the volume of a gas is directly related to the number of its moles when the temperature and pressure are not changed.
• Volume is directly proportional to the number of gas molecules.
• Dalton’s Law (also called Dalton's law of partial pressures) states that in a mixture of non- reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. This empirical law was observed by John Dalton in 1801 and published in 1802.
• In Dalton's Law, the total pressure of a mixture of gases equals the sum of the pressures each gas would exert independently.