Energy in Thermal Processes

1. Energy in Thermal Processes Heat Calorimetry Phase Changes

2. Heat and Internal Energy • _______ _______, U, is energy of atoms and molecules of a system • Includes KE of translation, rotation, vibration • Includes PE of chemical/electrical bonds • ______, Q, is transfer of energy between system and environment due to temperature difference ΔT

3. Units of Heat • Historically defined in terms of __________ _________ of object • calorie (cal) – the energy necessary to raise the temperature of 1g of water from 14.5°C to 15.5°C • British thermal unit (BTU) – the energy necessary to raise the temperature of 1 lb of water from 63°F to 64°F • Heat (like work) is a transfer of energy and has SI units of ________

4. Specific Heat • Every substance requires a ________ amount of energy per unit mass to change T by 1°C • Characterize the material by its _______ heat c • Units are J/(kg∙°C) • See Table 11.1, p. 355

5. Calorimetry • Use containers that are good ________ (no energy leaves/enters the container) • Put warmer and cooler materials in container • Apply conservation of ______ In general Sign of ____ takes care of sign of Q

6. Latent Heat and Phase Change • Sometimes energy transfer results in changes of ____ (melting/freezing = _____, boiling/condensing = _________) • _____________ does not change • Characterized by latent heat L • See Table 11.2, p. 360; units are J/kg Use + if ______ energy, – sign if _______ energy

7. Example: Ice to Steam Fig. 11.3, p. 361