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Unformatted text preview: LMLaput Chemistry 16 Lecture 7 THERMOCHEMISTRY HEAT and TEMPERATURE • HEAT –a form of energy that always flows spontaneously from a hotter body to a colder body, NEVER in the reverse direction. • TEMPERATURE –measures the intensity of heat. ¡ ¢ (£ ¤¥ ¦ §¨© ª §¨« ¤ ) ¬ ¥® ª ¯ ¢ §¨« ¤ §¨© ª °£ ª ± ® ª² ³ ¢ ¤ ¬ ®´¨§µ HEAT TRANSFER AND MEASUREMENT •SI unit J (Joule) •calorie - Amount of heat required to heat 1 g of water 1 °C - 1 calorie = 4.184 J •Calorie - Amount of heat required to heat 1 kg of water 1 oC •English unit = BTU •Specific Heat, J/g°C- Amount of heat required to raise the Temperature of 1g of a substance by 1°C •Heat capacity, J/mol°C- Amount of heat required to raise the T of 1 mole of a substance by 1°C HEAT TRANSFER ¶·¸¹º»º¹¥¼¸½¾ ¢ ½¿ÀÁÂ¾¥À»¥Ã¸½¾¥ºÂ¥Ä ¿½ÅÅ¥À»¥ÅÁÆÅ¾½Â¹¸¥ºÂ¥Ç¥ ¦ ¾¸¿·¸È½¾ÁÈ¸¥ºÂ¥ ¤ q = mcΔT •q= heat ( Joules, J ) •m = mass ( grams, g ) •c = specific heat ( J/g°C ) •ΔT = temperature change ( °C) q = CΔT •q = heat ( Joules, J ) •C = heat capacity ( J/mol°C ) •ΔT = temperature change ( °C ) FIRST LAW OF THERMODYNAMICS •This law can be stated as, “ The combined amount of energy in the universe is constant .” •The first law is also known as the Law of Conservation of Energy. – Energy is neither created nor destroyed in chemical reactions and physical changes. THERMODYNAMIC TERMS •SYSTEM - The substances involved in the chemical and physical changes under investigation. •SURROUNDING - The environment around the system •UNIVERSE - The system plus the surroundings CHANGES IN INTERNAL ENERGY, ΔE •The internal energy, E, is ALL of the energy contained within a substance. – This function includes all forms of energy such as kinetic, potential, gravitational, electromagnetic, etc....
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