have you ever noticed that a ball or really any inflated object seems to feel different at different points in the year in the summer a properly inflated basketball will feel firm and have a proper bounce but that same ball might feel softer in the winter similarly a car tire on a cold morning may report low tire pressure and be seemingly fixed by the afternoon heat although many inflated objects will slowly deflate PL over time these changes may also be related to the natural behavior of gases this behavior is not only dependent on the quantity of a gas but also its conditions such as temperature volume and pressure in this video we'll explore the properties of idol gases and the conditions under which real gases deviate from ideal Behavior we also delve into the molar volume of a gas at standard temperature and pressure and solve problems using the idal gas equation and combined gas law most gases that we interact with on an everyday basis and in the lab are considered ideal what does that really mean let's start with a couple assertions an ideal gas consists of moving particles with negligible volume and will feel no intermolecular forces when they collide with other gas molecules or the walls of their container we can make these assertions for good reason in terms of magnitude of size gases are much smaller than the containers in which they typically exist so much so that we could ignore their individual volumes gas particles are also spaced relatively far apart and are constantly moving at high speeds this means they won't have much opportunity or ability to Fu intermolecular attractive forces with other part particles as a result collisions between particles are considered elastic meaning no kinetic energy is lost during the Collision this is the difference between colliding two chunks of clay which will stick to each other and form a clump falling to the ground and colliding to Billiard balls which bounce off one another with no real loss of kinetic energy with no intermolecular forces gas particles will simply not stick to each other upon Collision with this in mind there are of course conditions that will cause gases to deviate from this behavior and act as real gases these conditions negate the assertions we made from before and force us to contend with intermolecular forces and molecular volume particularly we see this at low temperatures and high pressures at low temperatures particles move slower and intermolecular forces become more significant we no longer have elastic collisions at high pressures the volume of the particles themselves becomes significant compared to the overall volume of the container we can no longer ignore them these conditions ultimately lead to deviations from the idog gas model but outlining the ideal behavior of most gases is really important for our conceptual understanding and for making our lives easier when it comes to completing calculations namely we see this in the ideal gas equation PV equals nrt this powerful equation demonstrates the relationship between the pressure volume temperature and the amount of an ideal gas pressure p is measured in pascals and is the result of the force created by the collisions of gas particles the walls of their container volume v is the volume of the container measured in me cubed moles N is a way for us to count the number of gas particles and temperature T represents the energy of the particles and is measured in the unit Kelvin R in this equation stands for the universal gas constant equaling 8.314 Jew per mole Kelvin this constant makes our equation true and as the name suggests will not change if you're new to the unit Kelvin this measurement of temperature tempature follows the same unit scaling as Celsius but with one large distinction while the Celsius scale extends into the negative degre the Kelvin scale shifts everything down so that our temperature values start at Absolute Zero thus to relate Kelvin and deg Cel we follow this relationship Kelvin equals de Cel plus 273.15 not only will this equation help us solve calculation involving gases under various conditions we can also use it to tease apart relationships between pressure volume temperature and moles to better understand how these ideal gases behave one such calculation that is solved by the ideal gas law is that of the molar volume of an ideal gas at standard temperature and pressure known as STP at STP temperature is measured at 273.15 Kelvin and pressure at 100 kilop Pascal or 100,000 pascals if we rearrange our ideal gas equation to solve for the volume of one mole of a gas and plug in our values at STP we find that one mole of an idal gas will always have a volume of 0.227 M cubed or more commonly 22.7 decim cubed we could then use this as a conversion factor let's see this in in Action a helium balloon has a volume of 2.0 DM cubed at STP what mass of helium is contained within this balloon to start we'll find the moles of helium in the balloon using the volume of a gas at STP as our conversion factor from there we can multiply our M amount by the M mass of helium where one mole of helium weighs 4. G we find that our 2 decim cub balloon contains 0.35 G of helium ultimately the idro gas law is a powerful tool that unites three fundamental gas laws Bo's law gac's law and Charles's Law Bo's law states that the pressure of a gas is inversely proportional to its volume when temperature and moles are held constant remember pressure is the result of gas particles colliding with the walls of their container so if the container volume is reduced the number and rate of these collisions will increase and therefore so will the pressure in other words for this inversely proportional relationship if you decrease the volume of a gas its pressure increases and vice versa we can derive the equation for this relationship using the idal gas law consider a gas whose container has changed volume we can use the idog gas law to Define this gas and its initial in final conditions remember that for this example temperature and moles must be held constant this means that between these conditions only pressure and volume are changing which will Mark as P1 and V1 for the initial conditions and P2 and V2 for the final conditions notice that although these variables have changed they're both equal to the same constants nrt so if P1 * V1 = nrt and P2 * V2 = nrt then P1 * V1 and P2 * V2 must equal each other this equation defines the mathematical relationship between pressure and volume as outlined in Bo's law P1 * V1 equal P2 * V2 gusc law states that the pressure of a gas is directly proportional to its temperature in a rigid container where volume and mole are held constant the speed at which gases move is in part determined by their temperature therefore increasing the temperature of a gas for example would cause those particles to move faster leading to more frequent collisions with their container and therefore create a higher pressure pressure and temperature are proportional which means that heating a gas will increase its pressure and cooling a gas will decrease its pressure assuming volume stays the same we could again derive the equation for this relationship using the idog gas law this time pressure and temperature are our changing variables and if we solve for these variables we find that they are both equal to our constants n r/ v showing that P1 / T1 and P2 / T2 must equal each other this defines a relationship between changing pressure and temperature as outlined by GAC gas law P1 / T1 equals P2 / T2 Charles's Law tells us that the volume of a gas is directly proportional to its temperature in a flexible container where pressure and moles are constant this is a little bit different than our last example think of a flexible container like a balloon if you warm a balloon the previous gas law states that the internal pressure will increase due to the increase of collisions with gas partic and the walls of the balloon flexible containers are particularly sensitive to the internal pressure of the gas they contain and the external pressure of the gases in their surrounding atmosphere when these forces are not equal a flexible container will expand or contract until they're balanced in this case the balloon will expand upon being heated until the internal and external pressures become equal under our new conditions temperature tempature and volume are proportional which means that increasing temperature will increase volume and vice versa in a flexible container we can again derive the equation for this relationship using the idog gas law this time volume and temperature are the changing variables and if we solve for these variables we find that they're both equal to our constants in r/ P showing that V1 over T1 and V2 over T2 must be equal to each other this defines our relationship between changing volume and temperature as outlined in Charles's Law V1 / T1 equals B2 / T2 the combined gas law brings these three relationships together into a single equation P1 V1 / T1 equal P2 V2 over T2 this equation is particularly useful as it allows us to predict the new state of a gas given its initial conditions and any changing variables let's say for example you have a gas with an initial pressure of 101 kilopascals a volume of 10 m cubed and a temperature of 300 kelv if the volume of this gas is changed to 5 m cubed and its temperature to 200 Kelvin what would be the gas's new pressure well in this problem pressure V and temperature are all changing in fact we can identify each variable within our question this means we'll need to use our combined gas law to start we'll rearrange the equation to solve for P2 the new pressure of the gas inside the container from there we can plug in values for our variables being sure to convert our pressure into pascals and we find that the final pressure in our container equals 135,000 pascals in summary we've covered the key assertions and limitations of the idog gas model we learned about the M volume of an ideal gas at STP and how real gases deviate from ideal Behavior under certain conditions we also explored the ideal gas equation gas laws that show specific relationships between our variables and the combined gas law that brings it all together understanding these Concepts allows us to gain insights into the behavior of gases in various situations providing not only a foundation for more complex Topics in chemistry but a better understanding of the world around us and the gases that we interact with on a daily basis