Atmospheric Pressure:

• Atmospheric pressure is the force exerted by gas molecules in the air as they strike surfaces.

• Measured using a barometer (invented by Torricelli); standard atmospheric pressure is 760 mm Hg.

• Common units: atm, mm Hg, torr, Pa, psi. 1 atm=760 mm Hg=101325 Pa

Gas Laws:

• Boyle's Law: At constant temperature, pressure and volume are inversely proportional. P1V1=P2V2

• Charles' Law: At constant pressure, volume and temperature (in Kelvin) are directly proportional. V1T1=V2T2

• Avogadro's Law: At constant temperature and pressure, volume and number of moles are directly proportional. V1n1=V2n2

• Combined Gas Law: Relates pressure, volume, and temperature for a fixed amount of gas. P1V1T1=P2V2T2

• Ideal Gas Law: Relates pressure, volume, temperature, and moles of a gas. PV=nRT Where R = 0.0821 L·atm/(mol·K).

Problem-Solving Tips:

• Convert all temperatures to Kelvin: T(K)=T(°C)+273

• Use appropriate gas law based on which variables are held constant or changing.

• For combined or ideal gas law problems, ensure all units are consistent (e.g., pressure in atm, volume in L, temperature in K).

• When solving for changes, identify initial and final states and apply the correct law.

Conceptual Understanding:

• Gases exert pressure due to molecular collisions with surfaces.

• Volume, pressure, temperature, and amount of gas are interrelated; changing one affects the others according to the gas laws.

• Understanding these relationships is essential for predicting gas behavior in different scenarios.