Gases

Nature of Gases Gases have mass They are easily compressed Gases fill their container completely Different gases can move through each other quite rapidly ( diffusion ) Gases exert pressure The pressure of a gas is dependent on the temperature.

Additional Properties Expansion – spread out to fill their container Fluidity – they flow Low Density- particles are 1000 times farther apart in a gas than either a solid or a liquid Compressibility – these particles can be pushed together Diffusion – spontaneous mixing of two substances, by random movement Effusion- passing through tiny holes, why He leaks out of a balloon

Kinetic-Molecular Theory The Kinetic is used to explain why the gases behave the way they do. It has about 6 assumptions

Gases are made up of tiny winy itsi bitsy yellow poka dotted particles( atoms) The particles are in constant motion, they never stop. They have perfectly elastic collisions They exert no force on one another, attraction or repulsion. The average kinetic energy of a gas depends on the temperature Gases that do the above are called Ideal Gases

Pressure pressure = force per unit area or force area Pressure is caused by the collisions of the particles with themselves and their container per unit time

Any thing that changes the number of collision per unit time will change pressure. Amount of gas Size of container temperature

Boyles law “J” tube

Measuring air pressure Torricelli- the barometer

Units of air pressure All are standard pressure at sea level 760 mmHg 760 Torr 1 atm 101.3Kpa 14.7 psi 1013 mb 29.9 in.