Ideal Gas Law Why bother with Gases? Properties of a Gas Animation P, V, T, n Ideal Gas Law Examples of Ideal Gas Law Ideal Gas Law - #molecules version

Temperature and Gases Gas – Simplest material phase – all kinetic energy. – Energy “reservoir” – convert disordered KE to useful mechanical work. Properties of a Gas – Pressure – Volume – Temperature – Quantity 4 Properties are interrelated – Animation – Ideal gas law

Ideal Gas Animation Gas/piston animation (Java animation) ……..…… Gas/piston animation Other animations

Ideal Gas Observations Observations of P, V, T, n – Pressure vs. Volume (Boyle’s Law) P proportional to 1/V – Volume vs. Temperature (Charle’s law) V proportional to T – Pressure vs. Temperature (Gay-Lussac’s Law) P proportional to T – Pressure and volume vs. quantity PV proportional to n

Ideal Gas Law – Primary units Ideal gas law combines Boyle’s, Charles, Gay-Lussac’s PV = nRT – P proportional 1/V – V proportional T – P proportional T – P proportional n Units – P in Pascals = N/m 2 – V in m 3 – T in K° (not C °) – n in moles – R = J/mol-K Definition of Mole n = mass/molecular mass (N 2 =28g/mol, O 2 = 32g/mol, etc.)

Ideal Gas Law – Alternative units Ideal gas law combines Boyle’s, Charles, Gay-Lussac’s PV = nRT – P in atmospheres – V in liters – T in K° – n in moles – R =.0821 L-atm/mol-K Use either primary units or alternative units completely, don’t mix n’ match! Use primary units for First Law (Ch 15) calculations.

Celsius vs. Kelvin

Example volume 1 mole at STP

Example helium balloon

Example mass of air in room

Example – automobile tire

More examples of ideal gas Problem 29 V 2 = V 1 (P 1 /P 2 ) (T 2 /T 1 ) Problem 30 T 2 = T 1 (P 2 /P 1 ) (V 2 /V 1 ) Problem 31 ρ = 32 x /22.4 x Problem 32 P 2 = P 1 (n 2 /n 1 ) Problem 33 Problem 36 n 2 = n 1 (P 2 /P 1 ) Problem 39 P 2 = P 1 (V 1 /V 2 )(T 2 /T 1 )

Problem 29 – V change with P, T

Problem 30 – T change with P, V

Problem 31 – Density of O 2

Problem 32 – Gas substitution

Problem 36 – Gas substitution

Problem 39 – P change with V, T

Ideal Gas Law - #molecules version