Atmospheric Pressure:

• Atmosphere supports life, removes waste gases, and protects from radiation.

• All gases exert pressure on their surroundings due to molecular collisions.

• Atmospheric pressure is the force exerted by air molecules on Earth's surface; measured using a barometer (standard pressure = 760 mmHg).

• Factors affecting barometric pressure include altitude and weather conditions.

Units of Pressure:

• Common units: mmHg, torr, atm, Pa, psi.

• Conversion: 760 mmHg=1 atm=101325 Pa=14.7 psi

Gas Laws:

• Boyle's Law: At constant temperature, pressure and volume are inversely proportional. PV=k P1V1P2V2=k

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

• Avogadro's Law: At constant temperature and pressure, volume and moles of gas are directly proportional. Vn=k 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 gas. PV=nRT Where R = 0.0821 L·atm/(mol·K).

Problem-Solving Tips:

• Always convert temperatures to Kelvin (K = °C + 273).

• Use appropriate units for R in the ideal gas law.

• Identify which law applies based on which variables are held constant.

• For combined gas law and ideal gas law problems, set up equations with known and unknown variables, and solve algebraically.

Conceptual Understanding:

• Gas laws describe how gases respond to changes in pressure, volume, temperature, and amount.

• Understanding the relationships helps predict gas behavior in real-world and laboratory settings.