Characteristics of Gases
Unlike solids and liquids, gases have the following unique characteristics:
- 1. They have no definite shape or volume
- Gas particles move in all directions and can fill any part of a container. Therefore, the volume of a gas is equal to the volume of its container.
- 2. Gases are highly compressible
- Most of a gas is empty space, and the volume of the particles themselves is negligible. Assuming an ideal gas, the size of the gas particles is considered to be zero. This explains why gases are easily compressed when an external force is applied.
- 3. Gases are sensitive to temperature changes
- As temperature increases, gas molecules move faster and their volume increases. If the gas is contained in a container of constant volume, they collide with the container walls more frequently, increasing the pressure.
Conversely, as temperature decreases, molecular motion slows and the volume decreases. If the volume is constant, the pressure decreases as the number of times it collides with the walls of the container decreases.
Two gases facing a flexible partition (middle piston)
In the above simulation, you can unlock by clicking the locked icon. In this case, the two gases interact with each other through pressure.
- The pressures of the two gases eventually become equal.
- Pressure refers to the force that gas molecules exert on the walls of a container. Let’s assume the pressures of the two gases are different. In this case, the partition will move until the pressure difference is eliminated, which will eventually disappear.
- The volume ratio of a gas is proportional to the number of gas particles and the temperature of the gas.
- Let n1 be the number of particles in region A and T1 be the temperature, and n2 be the number of particles in region B and T2 be the temperature, then the following formula holds:
Volume of region A : Volume of region B = n1 × T1 : n2 × T2
Two gases facing a fixed partition
In the above simulation, you can lock the bulkhead by mouse drag.
This means that the gases in spaces A and B have no influence on each other. In other words, the two gases are independent of each other and each satisfies the ideal gas equation of state separately.