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Gas has existed since the beginning of time; often, it was referred to as “air” or “oxygen;” however, in the late 18th century, “air” became known as gas, and people were able to distinguish between different types of gas. Towards the end of the 18th century, scientists started testing and developing laws that later became known as the “gas laws.” These laws describe properties of gases, and how they react in different situations.

Gases appear to us as material of very low density that must be enclosed to keep together. Unlike solids, gases have no definite shape. electricity merit badge requirements Unlike liquids, gases have no definite volume, but they completely fill a container. The volume of the container is the volume of the gas in it. A gas exerts a pressure on all sides of the container that holds it. Gas can be compressed by pressures greater than the pressure the gas on its container. The words vapor, fume, air, or miasma also describe a gas. Air describes the common mixture of gases in the atmosphere. A miasma is usually a bad-smelling or poisonous gas. The words vapor and fume suggest that the gas came from a particular liquid.

In the gaseous state matter is made of particles (atoms or molecules) that are not attached to each other. The intermolecular or interatomic forces that hold solids and liquids have been overcome by the motion of the molecules. The particles of a gas have too much thermal energy to stay attached to each other. The motion and vibration of the atoms pull the individual molecules apart from each other.

Air in the gas phase at standard temperature and pressure (1 atmosphere of pressure and 0°C.) has a mol of it (28.96 g) in 22.4 liters, coming to about 1.29 grams per liter. gas near me now Liquid air is over 680 times denser than the air at one atmosphere. As an estimate, each molecule of gas in the air has 680 times its own volume to rattle around in. Gases are mostly unoccupied space. Each molecule of a gas can travel for a long distance before it encounters another molecule. We can think of a gas as having a ‘point source of mass’, that is, the volume of the molecule is negligible compared to the space it occupies.

When a gas molecule hits another one, they bounce off each other, ideally in a completely elastic encounter. There is pressure within the gas that is caused by the gas molecules in motion striking each other and anything else in the gas. The pressure that a gas exerts on its container comes from the molecules of gas hitting the inside of the container and bouncing off.

A gas may be completely described by its makeup, pressure, temperature, and volume. The Ideal Gas Law is used when you are given 3 of the 4 variables (you always have R, so that doesn’t count as a variable), where P is the pressure, V is the volume, n is the number of mols of gas, T is the absolute temperature, and R is the Universal Gas Constant:

This formula is the "Ideal Gas Law Formula." The formula is accurate for all gases as we assume that the gas molecules are point masses and the collisions of the molecules are totally elastic. (A completely elastic collision means that the energy of the molecules before a collision equals the energy of the molecules after a collision, or, to put it another way, there is no attraction among the molecules.) The formula becomes less accurate as the gas becomes very compressed and as the temperature decreases. There are some correction factors for both of these factors for each gas to convert it to a Real Gas Law Formula, but the Ideal Gas Law is a good estimation of the way gases act. We will consider only the Ideal Gas Law Formula here.

The Combined Gas Law Formula is the relationship of changing pressure, temperature, and volume of an ideal gas. The same amount of the same gas is given at two different sets of conditions. Let’s call the first set of measurements, ‘condition #1,’ and the second set of measurements, ‘condition #2.’ We could label the pressure, temperature and volume symbols each with the subscripted number of the condition it represents. P1 is the pressure at condition #1. P2 is the pressure at condition #2. V1 is the volume at condition #1, etc. The gas laws apply to both conditions, so P1 V1 = n R T1 and P2 V2 = n R T2. R is always the same Universal Gas Constant. If we are considering the same gas only at two different conditions, then n1 = n2. electricity and magnetism connect to form Since they are both equations, we could divide one equation by the other to get:

This law is about pressure and volume relationships, therefore it assumes constant temperature, meaning the temperature does not change. Boyle’s Law is useful when we compare two conditions of the same gas with no change in temperature. (Remember, "Always Boyle’s at the same temperature!") No change in temperature means T 1 = T 2, so we can cancel the two temperatures in the Complete Gas Law Formula and get:

This law states that pressure and volume are inversely proportional. That means that as one gets larger, the other gets smaller. The 1 and 2 indicate change. P 1 would be before the pressure change, and P 2 would be after the pressure change. This law can also be written like this: PV = k 1 which means that pressure multiplied by volume gives you a constant, k. This is not the same constant for every reaction; it differs from gas to gas. Charles’s Law

To get a better feeling for Charles’ Law, consider a child’s toy balloon. la gasolina reggaeton explosion At points between the beginning of filling of a balloon and the maximum stretching of a balloon, the change in internal pressure of a balloon is negligible as the balloon increases in size. A balloon is partially filled at room temperature and placed in the sun inside a car on a hot day in summer. The balloon expands in proportion to the Kelvin temperature. When the same balloon is take out of the car and put into a home freezer, the volume of the balloon decreases. Gay-Lussac’s Law (The Third Law)

The third gas law from the Combined Gas Law has been named for Gay-Lussac in some books, Amonton in others, and not named in a large number of books. It is sometimes amusing to read a book that does not name the third law and needs to refer to it. The third law is the relationship of pressure and temperature with constant volume ( V 1 = V 2.) the pressure and absolute temperature of a gas are directly proportional.

To get a feel for the third Law, consider an automobile tire. With a tire gauge measure the pressure of the tire before and immediately after a long trip. When cool, the tire has a lower pressure. As the tire turns on the pavement, it alters its shape and becomes hot. There is some expansion of the air in the tire, as seen by the tire riding slightly higher, but we can ignore that small effect. gas meter reading If you were to plot the temperature versus pressure of a car tire, would zero pressure extrapolate out to absolute zero? Remember what you are measuring. The pressure of a car tire is actually the air pressure above atmospheric pressure. If you add atmospheric pressure to your tire gauge, you would certainly come closer to extrapolating to absolute zero. Gas Stoichiometry Math

As you know from the Mols, percents, and stoichiometry section, stoichiometry is the calculation of an unknown material in a chemical reaction from the information given about another of the materials in the same chemical reaction. What if either the given material or the material you are asked to find is a gas? In stoichiometry you need to know the amount of one material. For gases not at STP, you must know the pressure, temperature, and volume to know the amount of material given. If you are given a gas not at STP, you will be able to substitute P V = n R T for the given side and plug it directly into the mols place by solving the equation for ‘ n’. Here is a sample problem using a gas not at STP as the given.

Things are a bit different when you need to find the volume, pressure, or temperature of a gas not at STP. You will need to solve P V = n R T for the dimension you need to find and attach it to the end of the sequence using the roadmap to find ‘ n’ for the gas. Let’s take another problem based on the same chemical equation to explore how to set up finding a gas not at STP.

A 20.6 liter tire at 23°C and 3.21 Atmospheres inside pressure is run on the Interstate for four hours. The tire is now 20.8 liters at 235°C. What is the pressure in the hot tire? You must group the V = 20.6 liters, P = 3.21 Atmospheres, and T = 296 K as one condition. Each of these measurements must have the same subscript, whatever you choose. For instance, V 1 = 20.6 liters, P 1 = 3.21 Atmospheres, and T 1 = 296 K The second condition has a missing component. You are given the volume and temperature, but not the pressure. V 2 = 20.8 Liters, T 2 = 508 K, and you need to find P 2.

If the volume is proportional to the number of mols of a gas, there is a constant, k, that we can use in the formula, V = k n, to express the proportionality of V and n. What is that proportionality constant? At standard temperature and pressure, the pressure is one atmosphere and the temperature is 273K. The Universal Gas Constant is still 0.0821 Liter – atmospheres per mol – degree. Let’s set n at one to find out what k is.

Similarly to the way we derived V = k n for Avogadro’s Law above when the pressure is constant, we can derive P = k n for conditions when the volume does not change. electricity distribution vs transmission This time there is no notable significance to the k, so we will just say that P is proportional to n when the temperature and pressure are constant. In conditions when more than one gas is mixed, we could number and add the pressures and mols. If we were to have P 1 of gas #1 due to n 1 mols of it and P 2 of another gas (#2) due to n 2 mols of it, those two gases in the same volume (They must be at the same temperature.) can be added together. P T is the total pressure and n T is the total number of mols.

This has nothing to do with whether gas #1 is the same as gas #2. Dalton’s Law of Partial Pressures says that, "The sum of all the partial pressures of the gases in a volume is equal to the total pressure." Where P T is the total pressure, P 1 is the partial pressure of ‘gas #1’, P 2 is the partial pressure of ‘gas #2’, P n is the pressure of the last gas, whatever number (n) it is. Graham’s Law of Diffusion (or Effusion)

The mental picture of diffusion could be the drop of ink (with the same specific gravity as water) being carefully placed in the center of a glass of water. The ink will diffuse from the original point where it was deposited with no mixing of the glass of water. The mixing of diffusion is due to the movement of the molecules. (You can actually SEE this if you make an almost saturated solution of sugar and put a small amount of dye in the mixture. gastroenterology Slowly pour the mixture down the side of a clear container partly filled with water, and place the container on a surface that will not be moved. The syrup mixture will drop to the bottom of the water and make a sharp line between the liquids. As days pass, you will see that sharp line blur, and, as weeks pass, the line may disappear completely.) Gases diffuse much more quickly than liquids because the energy of motion is higher and the available path for unobstructed straight movement is much greater in gases.

3. An enormous (57,400 cubic meter) expandable helium balloon at 22°C is heated up by a fire under it and the action of the sun on the dark plastic covering on top. There will be a small increase in pressure from 785 mmHg to 790 mmHg, but the major effect wanted is an increase in volume so the balloon can lift its cargo. To what temperature must the balloon get in order to fill out to 60,500 cubic meters?

8. The usual partial pressure of oxygen that people get at sea level is 0.20 Atm., that is, a fifth of the usual sea level air pressure. People used to 1 Atm. air pressure begin to become "light-headed" at about 0.10 Atm oxygen. As a rule of thumb, the air pressure decreases one inch of mercury each thousand feet of altitude above sea level. At what altitude should airplane cabins be pressurized? Up to about what altitude should you be able to use unpressurized pure oxygen? (Express your answer in feet above Mean Sea Level, or MSL.)