# Gas in Various Condition

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## Nature of gas

Since the gas can not be seen or touched, a little imagination is needed to understand the ‘nature of the gas.’ In most everyday life, people often do not perceive air. This makes it difficult to understand the gas.
The gas has the following properties.

1. Even if the gas is collected in one place in the container, it spreads quickly and fills the entire container evenly.
2. Gases compress more easily than liquids or solids.
3. Gas molecules are farther apart than liquids or solids.
4. Gas molecules have very little pulling force.

## Movement of gas molecules and pressure of gas

If you blow the rubber balloon, the rubber balloon will stretch. Because the air moves into the rubber balloon, so you can feel the force that the air pushes.
The gas molecules in the rubber balloon are constantly moving. And making collisions to the walls of the rubber balloon. At this time, the gas molecules’ force acts as pressure, and the rubber balloon becomes taut.
On the other hand, the more air is blown into the rubber balloon, the larger the rubber balloon. This is because the larger the number of gas molecules, the greater the rubber balloon’s pressure.

## Equation of state for ideal gases

The following four variables are used to formulate the state of the gas.

1. Pressure (P)
2. Volume (P)
3. Number of gas molecules (n)
4. Temperature (T)

In a closed system, the relationship between these four variables is:

1. As the number of gas molecules (n) increases, the pressure (P) or volume (V) increases.
2. The pressure (P) or volume (V) increases as the temperature (T) increases.
3. When the number of gas molecules (n) and temperature (T) is constant, pressure (P) and volume (V) are inversely proportional to each other.

We can express the above relations in one proportion.

P V ∝ n T

By inserting a proportional constant, you can express it as:

P V = n R T

P: pressure of gas (atm)
V: volume of gas (L)
n: number of gas molecules (mol)
R: proportional constant (= 0.082)
T: Temperature of gas (absolute temperature, K)