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# Chemistry - Introduction to Gases

We use phase to express the state of a matter. For example, there are:

• Gas phase

• Liquid phase

• Solid phase

In this topic, we are going to discuss more on Gas Phase.

Some physical properties of gases:

1. They occupy far more space than the liquids or solids.

2. They are easy to compress and expand.

3. They exert pressure.

From these properties, we can know that the studies of gases are much related on:

1. Volume (They occupy spaces)

2. Temperature (They compress and expand easily when is cooled or heated)

3. Pressure (They exert pressure)

This is true for the following gas law and we shall discuss these in my future post, which is:

• Boyle's Law

• Charles' Law

• Graham's Law of Diffusion

• Gay-Lusaac's Law

• Ideal Gas Law

Some more notes:

1. Gases occupy space by diffusion.

2. Brownian Motion is a phenomena whereby small particles suspended in a liquid tend to move in random paths through the liquid, even if the liquid is calm. This can explain why gases exert pressure.

3. $$\text{STP}$$ refers to Standard Temperature and Pressure, which is $$273K$$(or $$0^\circ C$$) and $$1\text{ Bar}$$(or $$100000\text{Pa}$$) .

4. In $$\text{STP}$$, $$1\text{ mol}$$ of gases(any gases!) occupy a volume of $$22.4L$$.

EDIT: Thanks to Anish Puthuraya for some informations on the $$\text{STP}$$.

Note by Christopher Boo
3 years, 7 months ago

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I have noticed that my previous note did not cover these so I add it on this introductory post. · 3 years, 7 months ago

I just want to notify that, the Standard Pressure is not 1 atm anymore.
It is 1 Bar, which is exactly $$10^5Pa$$
But, that's just a minor detail.

Anyway, looking forward to your next posts. · 3 years, 7 months ago

Do we also changed the value of 22.4L? This is because when I use 1 bar on my calculations, 1 mol gas will occupy a volume of 22.7L. · 3 years, 7 months ago

It is actually 22.7L. But, even I have been taught that 1 mole of gas occupies 22.4L of space.

So, even though this is incorrect, I think it would be better to stick with 1 atm, and 22.4L because most of the problems that are presented in this topic, assume it to be true. · 3 years, 7 months ago

Wow, thanks for telling me that! · 3 years, 7 months ago

I am waiting for your posts on the gas laws and Brownian motion and lots of your amazing problems. · 3 years, 7 months ago

I'll try my best! · 3 years, 7 months ago

You are a truly brilliant guy but don't overburden yourself. · 3 years, 7 months ago

The chemistry guys youre doing an awesome job....even though I specialize in math and computer science I studied chemistry at high school...its a nice refresher,..,, · 3 years, 7 months ago

There are five states of matter, by the way. Anyway nice post,Christopher. · 3 years, 7 months ago

Yes, Plasma and Bose-Einstein Condensate are the last two. But, the discussion is about gases, so considering the phase changes that gases go through, I think these 3 are enough. · 3 years, 7 months ago

Yeah well, when it comes down to quantum mechanics, there are even more... than that. Like a truck load of states. X'D For now, I think following the "KISS" principle is preferred. ^^ · 3 years, 7 months ago

What is that principle? · 3 years, 7 months ago

"Keep it simple stupid." Hahah, a person I love said that. Never really knew where it came from but lul. · 3 years, 7 months ago

Where are the other three laws? · 3 years, 6 months ago

What does "mol" means? · 3 years, 6 months ago

A "mol" is nothing but a unit for measuring the number of something. Its value is : $$6.022\times 10^{23}$$

So, $$1 mol$$ of a substance means that there are $$6.022\times 10^{23}$$ molecules/atoms of the substance present · 3 years, 6 months ago

Thanks · 3 years, 6 months ago

Nice and simple, very nice. I like it. · 3 years, 7 months ago

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