Which quantity is held constant when working with Boyle’s, Charles’s, and Gay-Lussac’s laws? volume moles pressure temperature

The content that follows is the substance of lecture 18. In this lecture we cover the Gas Laws: Charles',Boyle's,Avagadro's and Gay Lussacs as well as the Ideal and Combined Gas Laws.

Laws of Gas Properties

There are 4 general laws that relate the 4 basic characteristic properties of gases to each other. Each law is titled by its discoverer. While it is important to understand the relationships covered by each law, knowing the originator is not as important and will be rendered redundant once the combined gas law is introduced. So concentrate on understanding the relationships rather than memorizing the names.

Charles' Law- gives the relationship between volume and temperature if the pressure and the amount of gas are held constant:

1) If the Kelvin temperature of a gas is increased, the volume of the gas increases. (P, n Constant)

2) If the Kelvin temperature of a gas is decreased, the volume of the gas decreases. (P, n Constant)

This means that the volume of a gas is directly proportional to its Kelvin temperature. Think of it this way, if you increase the volume of a gas and must keep the pressure constant the only way to achieve this is for the temperature of the gas to increase as well.Calculations using Charles' Law involve the change in either temperature (T2) or volume (V2) from a known starting amount of each (V1 and T1):

Boyle's Law - states that the volume of a given amount of gas held at constant temperature varies inversely with the applied pressure when the temperature and mass are constant.The reduction in the volume of the gas means that the molecules are striking the walls more often increasing the pressure, and conversely if the volume increases the distance the molecules must travel to strike the walls increases and they hit the walls less often thus decreasing the pressure.

Like Charles' Law, Boyle's Law can be used to determine the current pressure or volume of a gas so long as the initial states and one of the changes is known:

Avagadro's Law- Gives the relationship between volume and amount of gas in moles when pressure and temperature are held constant.

If the amount of gas in a container is increased, the volume increases.  If the amount of gas in a container is decreased, the volume decreases. This is assuming of course that the container has expandible walls.

The relationship is again directly proportional so the equation for calculations is

Gay Lussac's Law - states that the pressure of a given amount of gas held at constant volume is directly proportional to the Kelvin temperature.

Explanation:

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.