Gases

Properties of Gases

Fluidity - Gas particles move around freely with negligible attraction to fill the shape of their container.

Molar Volume - Gases are over 99% empty space. As a result, the size of the particles does not affect the volume. Equal amounts of any gas will occupy almost the exact same volume.

Properties of Gases

Compressibility - Gases can easily change volume by placing a force on its container. (Solids and liquids cannot)

Diffusion - Mixing of 2 gases due to their random motion. All gases diffuse, but at different rates.

Properties of Gases Pressure – Gas particles are moving

very fast and when they collide with their surroundings, they exert an outward force.

Due to expansion, gases will flow until pressure is equalized.

(ex: if a plane loses cabin pressure, the air will rush out until the pressure is equalized)

PressurePressure is measured in:a. atmospheres (atm) b. millimeters of mercury (mm Hg)c. pascals (Pa)

Atmospheric Pressure:1.00 atm = 101.3kPa = 760 mm Hg

PressureIf you increase the amount of gas in a container, you will increase the pressure of the gas. (ex: adding air to your tires increases the pressure)

PressureDalton’s Law of partial pressures - The pressure of a mixture of gases is equal to the sum of their individual partial pressures.

Ptotal = P1 + P2 + P3….

Pair = Pnitrogen + Poxygen + Pcarbon dioxide + Pwater vapor…

Pressure

Based on this table, if a chemical reaction done inside an enclosed container were to consume all of the oxygen, what would be the new pressure in kPa?

Pressure

A vacuum is created when all of the gases are removed from a volume.

Because there are no particles, there is no air pressure. (Empty space has been created.)A partial vacuum is any volume with less pressure than the surrounding air, but not a complete vacuum.

Pressure

Total Vacuum = 0 atmospheres

> 0 atm1 atm > Partial Vacuum

In many gas equations, you will be given conditions of “STP.”

STP = Standard Temperature and Pressure

S PT

Standard Temperature = 0 C or 273 K

Standard Pressure = 1.00 atm 101.3 kPa 760 mm Hg

Pressure and VolumeBoyle's Law – At constant temperature, the pressure of a gas is inversely proportional to its volume.

Pressure and VolumeBoyle's Law – At constant temperature, the pressure of a gas is inversely proportional to its volume.

Inhaling – your lungs expand their volume creating low pressure. Air then rushes in to equalize the pressure.

Exhaling – your diaphragm compresses your lungs into a smaller volume creating high pressure. Air then is expelled to equalize the pressure.

Pressure and VolumeBoyle's Law – At constant temperature, the pressure of a gas is inversely proportional to its volume.

P1 V1 = P2 V2Graph