doubt about the uncertainty of kinetic theory of gases

[yohai]

i was reading about the kinetic theory of gases and also about its assumptions. while reading, i felt a bit curious that why do we even need to count the  assumptions of ktg and why not just use them for every case

[studiot]

33 minutes ago, yohai said:

i was reading about the kinetic theory of gases and also about its assumptions. while reading, i felt a bit curious that why do we even need to count the  assumptions of ktg and why not just use them for every case

Hello we really need more information to be able to help you.

What do you mean by 'counting the assumptions' and where did that idea come from?

What do you mean by every case ?
What exactly are you using the kinetic theory to model ?

Boyles ,Charles or Avogadros Law, the ideal gas law, or the mechanism of pressure etc. ?

 

[exchemist]

1 hour ago, yohai said:

i was reading about the kinetic theory of gases and also about its assumptions. while reading, i felt a bit curious that why do we even need to count the  assumptions of ktg and why not just use them for every case

Do you mean the assumptions that the molecules engage in perfectly elastic collisions and that the volume they take up can be neglected? These are just the types of simplifying assumption that science theories often resort to, in order to build a simple, idealised model that is easy to work with. It is very often found that by working with simplified models one can get pretty close to predicting behaviour correctly. (Simplifying, in order to see the main thing that is going on, is a very useful way to approach many problems in life). 

What is also interesting is then to investigate the deviations of some real substances from the ideal behaviour predicted by the model. That can allow you to understand the particular extra effects that are responsible. In this example, the effect of the volume taken up by the molecules becomes important at high gas pressures (i.e. when the molecules don't have a lot of room to move around in). Similarly at very low absolute temperatures, the slight "stickiness" between molecules resulting from van de Waals attraction between them can be important.  Both cause deviations from the simple kinetic theory model (and in fact van der Waals himself developed revised equations to account for each of these effects).  

So the basic model explains most of what is observed, while studying the deviations gives you a more complete level of understanding.

Edited 6 hours ago by exchemist

[sethoflagos]

2 hours ago, yohai said:

i was reading about the kinetic theory of gases and also about its assumptions. while reading, i felt a bit curious that why do we even need to count the  assumptions of ktg and why not just use them for every case

Because almost all of the assumptions are only approximations of real world gas behaviour under similar atmospheric conditions to those we are all routinely familiar with at earth's surface. 

For simple, non-critical cases these approximations are often close enough for the differences to be unimportant. 

However, for more complicated, more critical situations, it is necessary to replace the less valid assumptions with empirically grounded correlations specific to the use-case. And to do this you need a thorough working understanding of what those assumptions are in the first place. 

O, yes and in passing - if you don't have that thorough working understanding, you don't even get to judge what counts as simple and non-critical.

Edited 5 hours ago by sethoflagos