chemistry 103 ch 5-7

chemistry 103 ch 5-7 - Chemistry 103 Chapter 5 Most of the...

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Chemistry 103 Chapter 5 Most of the energy we use is obtained by carrying out chemical reactions, mostly by burning fossil fuels Energy is used for heating, electrical power, and for carrying out life processes. Thermodynamics-the science of heat and work 5.1 Energy: Some Basic Principles Energy = the capacity to do work For humans, energy is provided by food which is energy stored in chemical compounds and released during metabolism Energy is classified into 2 categories: Kinetic energy-energy associated with motion o The motion of atoms, molecules, or ions at the submicroscopic (particulate) level (thermal energy). All matter has thermal energy. o The motion of macroscopic objects like a moving tennis ball or automobile (mechanical energy). o The movement of electrons through a conductor (electrical energy). o The compression and expansion of the spaces between molecules in the transmission of sound (acoustic energy). Potential Energy-results from an object’s position o Energy possessed by a ball held above the floor and by the water at the top of a waterfall (gravitational energy). o Energy stored in fuels (chemical energy). All chemical reactions involve a change in chemical energy. o The energy associated with the separation of two electrical charges (electrostatic energy). Kinetic and Potential Energy can be interconverted (as water falls over a water fall, its potential energy is converted into kinetic energy) - Conservation of Energy The Law of Conservation of Energy-energy can neither be created nor destroyed (the total energy of the universe is constant). - Temperature and Heat Temperature is a way to measure an object’s ability to transfer energy as heat. When 2 objects at different temperatures are brought into contact, energy will be transferred as heat from the one at the higher temperature to the one at the lower temperature. Temperature determines the direction of thermal energy transfer. The higher the temperature of an object, the greater the thermal energy (energy associated with molecular motion) of its atoms, ions, or molecules. Heating and cooling are processes by which energy is transferred as heat from an object at a higher temperature to one at a lower temperature. Heat is not a substance.
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- Systems and Surroundings System = an object, or collection of objects, being studied. Surroundings = everything outside the system that can exchange energy and/or matter with the system - Directionality and Extent of Transfer of Heat: Thermal Equilibrium Energy transfer as heat will occur spontaneously from an object at a higher temperature to an object at lower temperature. Transfer of energy as heat continues until both objects are at the same temperature and thermal equilibrium is achieved.
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