physics chapter 12
DESCRIPTION
Thermal Energy NotesTRANSCRIPT
Chapter 12
Thermal Energy
Thermal Energy
• The thermal energy of an object is the sum of K.E. and P.E. of the internal motion of the particles that make up an object; it is dependent on mass
• The temperature of an object is the measure of how hot something is on a defined scale; this is the kinetic energy per molecule of an object; not dependent on mass
Thermal Energy
• When a cold object meets a hot object, the cold molecules speed up and the hot molecules slow down until they reach thermal equilibrium. (Zero’th Law of Thermodynamics)
Temperature Conversions
• F = 1.8C + 32
• C = 5/9 (F-32)
• K = C + 273.15
• Farenheit Celcius Kelvin
Physical States of Matter
6 States of Matter0. Einstein-Bose – no motion (no heat)1. Solid – definite shape and volume2. Liquid – definite volume and indefinite shape3. Gas – indefinite shape and volume4. Plasma – gaseous mixture of positively and
negatively charged particles5. Filament – non thermal motion in only one
direction
Heat
• The energy that flows as a result of a temperature difference: heat always flows from warmer regions to cooler regions.
• Specific Heat – amount of energy needed to raise or lower the temperature of a 1kg mass 1 degree Celsius
• Q = mC∆T
Heat –
Filter paper with and with out water
3 Types of Heat Transfer
• Conduction (requires contact) – transfer of K.E. when particles of an object collide
• Convection (requires mass flow) – transfer of heat through movement of fluids with different densities at different temperatures.
• Radiation (fastest) – transfer of heat through space by electromagnetic waves
3 Types of Heat Transfer
•
Heat of Fusion
• The amount of energy needed to melt or freeze 1kg of a substance. (The phase changes, but the temperature does not)
• Q = mHf
Heat of Vaporization
• The amount of energy needed to vaporize or condense 1 kg of a substance (The phase changes but the temperature does not)
• Q = mHv
Heating and Cooling
• Vaporization – cooling process because the faster moving molecules are escaping and leaving the cooler, slower molecules behind.
• Condensation – warming process because as the molecules condense more collisions occur, causing the object to gain heat.
Thermal ExpansionThermal Expansion
• In general, most things will expand when heated and contract when cooled.
• Linear Expansion
• L = Li + ∆L
• ∆L = αLi∆T
• Volume Expansion
• V = Vi + ∆V
• ∆V = βVi∆T
Natural ResourcesNatural Resources
►Sunlight (Solar-power) <1%Sunlight (Solar-power) <1%►Wind (Wind-power) 1%Wind (Wind-power) 1%►Rain (Hydro-power) 6%Rain (Hydro-power) 6%►Tides (Tidal-power, ocean currents) <1%Tides (Tidal-power, ocean currents) <1%►Wave (Wave-power, surface waves) <1% Wave (Wave-power, surface waves) <1% ►Geothermal Heat (Geothermal-Geothermal Heat (Geothermal-
power)<1%power)<1%
Solar & Wind & Tidal Solar & Wind & Tidal & Wave Power& Wave Power
Other Natural ResourcesOther Natural Resources
►Fossil fuels / Biomass Fossil fuels / Biomass (Non-renewable - Coal & Petroleum 86%)(Non-renewable - Coal & Petroleum 86%) (Non-renewable - Nuclear 6%) (Non-renewable - Nuclear 6%) (Somewhat renewable - Wood)(Somewhat renewable - Wood)
►Bio-fuel (Renewable plants used as Bio-fuel (Renewable plants used as fuel) fuel) Ex. E-10 gasolineEx. E-10 gasoline
Non-renewable energy Non-renewable energy sourcessources
►Natural gas (Methane) – CHNatural gas (Methane) – CH44
►Propane – CPropane – C33HH88
►CoalCoal►Oil, petroleumOil, petroleum►Uranium – NuclearUranium – Nuclear
Solar & Wind & Tidal & Wave Power
Advantages – Wide availability Very low emissions
Disadvantages – Tidal and Wave - Cost of harnessing &
building system (1st slated for 2012?) Solar & Wind not continuous (Cost of storing)
Hydro Power
Advantages – Low emissions
Disadvantages – Limited availability Ecological effect on rivers and streams
Natural Gas & Propane & Coal & Petroleum & Nuclear
Advantages Readily available Relatively low cost
Disadvantages Coal & Petroleum & Natural gas &
propane (Emissions) Nuclear (Storage or disposal of nuclear waste)
Wood & Plant Fuels
Advantages Somewhat easy to replenish
Disadvantages Ethanol (plant) fuels have to be replenished
adequately, otherwise this drives up cost of foods Wood has to be re-grown and harvested wisely,
otherwise this drives up costs of wood