Gases Nature of Gases Gases have mass They

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 mm. Hg 760 Torr 1 atm 101. 3 Kpa 14. 7 psi 1013 mb 29. 9 in.