Ch 16 Thermal Energy and Heat 16.1 Thermal Energy and Matter Work and Heat Heat is transfer of E from one object to another Moves from hot to cold objects Temp Avg KE of object 0K is absolute zero Thermal E Need mass, temp, and state of matter Total KE and PE of the motion of particles in the object
Thermal Contraction/Expansion Expansion: increase in volume due to temp increase Contraction: decrease in volume due to temp decrease Specific Heat Q= m x c x ΔT Heat = mass x specific heat x change in temp Calorimeter Measures heat flow
16.2 Heat and Thermodynamics Conduction Trans thermal E by touching between objects Faster in liquids/solids bc more particles touching Thermal conductors: material that transfer well Thermal insulator: material conducts poorly Convection Convection currents: warm rises and cold falls Air or water cycling Radiation Trans of heat by waves through space Think sun’s radiation!
First Law Thermodynamics Energy is conserved E cannot be created or destroyed, changes form Second Law Thermodynamics If thermal E flows from hotter to colder object Thermal E can only flow from colder object to hotter object if work is done to system Third Law Thermodynamics Absolute 0 (0K) cannot be reached No machine is 100% efficient so can only cool close to absolute zero
16.3 Using Heat Heat Engines External Combustion Internal Combustion Steam engine Burns fuel outside engine Internal Combustion Car engines Burns fuel inside engine Combustion engine with pistons that move up/down (strokes)
Heating Systems Central heating systems Hot-water heating Heats many rooms from one central location using vents Hot-water heating Boiler heats water and pumps it to where needed, cold water returned back Steam heating Steam is used instead of hot water Electric Baseboard Heating Electrical energy to heat room (like stove concept) heated coil warms air Forced-Air Heating Goal to maintain even room temp Heat vents on floor houses with real winters
Cooling Systems Heat pump reverses flow of thermal E Refrigerant fluid that vaporizes/condenses within tubes of heat pump Refrigerators Transfer of colder to warmer objects using heat pump