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Physical Science. Chapter 16: Thermal Energy and Heat 16.1 Thermal energy and Matter A. Work and Heat Heat is the transfer of thermal energy from on e object to another because of a temperature difference Heat flows spontaneously from hot objects to cold objects. B. Temperature Temperature is a measures of how hot or cold an object is compared to a reference point In the Kelvin temperature scale the reference point is absolute zero, which is defined as a temperature of 0 K. Temperature is related to the average kinetic energy of the particles in an object due to their random motions through space As an object heats up the particles move faster C. Thermal Energy Thermal energy is the total potential and kinetic energy of all the particles in an object Thermal energy depends on the mass, temperature, and phase (solid, liquid, or gas) of an object. An object with a higher temperature has a higher average kinetic energy D. Thermal Contraction and Expansion Thermal expansion is an increase in the volume of a material due to a temperature increase Thermal expansion occurs when particles of matter move farther apart as temperature increases Gasses expand more than liquids and liquids usually expand more than solids E. Specific Heat Specific heat (c) is the amount of heat need to raise the temperature of one gram of a material by one degree Celsius. The lower a material’s specific heat, the more its temperature rises when a given amount of energy is absorbed by a given mass Specific heat is measures in joules per gram per degree Celsius, or J/g∙C The heat (Q) absorbed by a material equals the produce of the mass (m), the specific heat (c) and the change in temperature (T). Heat is in joules, mass is in grams, specific heats is in J/g∙C, and temperature change is in C. F. Measuring Heat Changes A calorimeter is an instruments used to measure changed in thermal energy. A calorimeter used the principle that heats flows from a hotter object to a colder object until both reach the same temperature. According to the law of conservations of energy, the thermal energy released by the sample is equal to the thermal energy absorbed by its surrounds. 16.2 Heat and Thermodynamics A. Conduction Conduction is the transfer of thermal energy with no overall transfer of matter Conduction occurs within a material or between materials that are touching Conduction is gases is slower than in liquids and solids because the particles in a gas collide less often. In most solids, conduction occurs as particles vibrate in place and push on each other. 1. Thermal Conductors o Thermal conductor is a material that conducts thermal energy well o Metals conducts thermal energy very quickly o Tile is a better conductor than wood and transfers thermal energy 2. Thermal Insulators o Thermal insulator is a material that conducts thermal energy poorly o Air is a very good insulator o Wool garments and plastic foam cups are two more examples of insulators B. Convection Convection is the transfer of thermal energy when particle of a fluid move from one place to another Air circulating in an oven is an example of a convection current Convection current occurs when a fluid circulates in a loop as it alternately heats up and cools down. Convection currents are important in many natural cycles (ocean currents, weather systems, and moved of hot rocks in earth’s interior C. Radiation Radiation is the transfer of energy by waves moving through space Heat lamps and the sun are examples of radiations All objects radiate energy. As an object’s temperature increase, the rate at which it radiates energy increases. D. Thermodynamics Thermodynamics is the study of conversions between thermal energy and other forms of energy 1. First law of Thermodynamics o Energy cannot be created or destroyed but id can be converted into different forms. o The first law of thermodynamics stats that energy is conserved o If energy is added to the systems it increases the thermal energy of the system or does work on the system. 2. Second Law of Thermodynamics o Thermal energy flows spontaneously only from otter t colder objects o The second law of thermodynamics stats that thermal energy can flow form colder objects to hotter objects only if works is done on the system. o Heat engine is any device that converts heat into work. o The efficiency of a heat engine is always less than 100 % o Waste heat is thermal energy that is not converted into work o Waste heat is lost to the surrounding environment 3. Third Law of Thermodynamics o The efficiency of a heat engine increases with a greater difference between the high temperature inside and the cold temperature outside the engine o The thirds law of thermodynamics stats that absolute zero cannot be reached o Scientists have been able to cool mater almost all of the way to absolute zero o