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Heat is a transfer of energy (usually thermal energy) from a body of higher temperature to a body of lower temperature. Thermal energy is the energy associated with the random motion of atoms and molecules. (4.2a) • temperature The Law of Conservation of Energy states that energy can neither be created nor destroyed.
Kinetic molecular theory (KMT) for an ideal gas states that all gas particles (3.4b): • 1. are in random, constant, straight-line motion. • 2. are separated by great distances relative to their size; the volume of the gas particles is considered negligible. • 3. have no attractive forces between them. • 4. have collisions that may result in the transfer of energy between gas particles, but the total energy of the system remains constant.
Real Gases • Molecules do take up space • Molecules do attract each other • Energy is lost during collisions • Under conditions of high temperature and low pressure, real gases behave more like ideal gases • Small molecules take up little space and have weaker forces of attraction and are closer to an ideal gas • Hydrogen and helium are closest to being ideal gases
Kinetic molecular theory describes the relationships of pressure, volume, temperature, velocity, and frequency and force of collisions among gas molecules. (3.4c) P1V1 P2V2 T1 T2
Boyle’s Law Indirect Relationship between pressure and volume Temperature remains constant PxV = constant Charles’ law Direct relationship between volume and temperature Pressure remains constant V/T = constant Temperature must be Absolute temperature (Kelvins) Ideal Gas Laws
Regents Question: 06/02 #14 Which graph shows the pressure-temperature relationship expected for an ideal gas? þ
Graphing the gas laws As absolute temperature increases, pressure increases at constant volume Pressure Temperature As absolute temperature increases, volume increases at constant pressure Volume Temperature As pressure increases, volume decreases at constant temperature Volume Pressure
Equal volumes of different gases at the same temperature and pressure contain an equal number of particles. (3.4e) Avogadro’s Hypothesis
Regents Question: 06/02 #15 At the same temperature and pressure, which sample contains the same number of moles of particles as 1 liter of O2 (g)? (1) 1 L Ne(g) (3) 0.5 L SO2 (g) (2) 2 L N2 (g) (4) 1 L H2O(l) þ