Thermal Energy and Matter Ch 16.1

Thermal energy depends on mass, temperature and phases of the object True False Statement Heat, which is the flow of thermal energy, always flows from cold objects to hot objects Absolute zero is a reference point using the Kelvin scale, used to measure temperature Thermal energy depends on mass, temperature and phases of the object An object will expand in hot temperatures, and shrink in colder temperatures called thermal expansion/contraction Specific heat is how much heat is needed to raise the temperature of an object, and is the same for all objects

Work and Heat Heat- transfer of thermal energy from 1 object to another due to temperature difference Heat flows from hot objects to cold objects

Temperature Temperature- measure of how hot or cold an object is compared to a reference point °C= boiling/freezing point of water Absolute zero- reference point in K, which is 0K Temperature relates to the kinetic energy of particles hot= faster particles cold= slower particles

Thermal Energy Depends on: Mass Temperature Phase- solid, liquid, gas of an object

Thermal Contraction and Expansion Thermal Expansion- increase volume due to temperature increase Particles move farther apart Thermometers Increase temp. = alcohol moves/expands = temperature you read

Specific Heat Specific Heat- amount of heat needed to raise the temperature of 1g of material by 1°C The lower the SH, the more the temp. rises when a given amount of energy is absorbed by a given mass

Specific Heat Q = m c ΔT Q- heat absorbed by material, J M- mass, g C- specific heat, J/g°C ΔT- change in temp. °C

Specific Heat Practice An iron skillet has a mass of 500g. Its specific heat is 0.449 J/g°C. How much heat must be absorbed to raise the temperature by 95C? Given: Formula: Solve:

Math Practice pg 477 2. 4. 3. 5.

Measuring Heat Changes Calorimeter- sealed instrument used to measure changes in thermal energy Uses principle that hot energy flows to cold, until they equal the same temperature.

Heat and Thermodynamics Ch. 16.2

Conduction transfers thermal energy when 2 objects touch True False Statement Conduction transfers thermal energy when 2 objects touch Convection transfers thermal energy through moving fluids Radiation is the transfer of energy through space The 1st law of thermodynamics state energy is not created or destroyed The 3rd law of thermodynamics state you must reach absolute zero

Conduction Transfer of thermal energy between 2 touching objects, with no overall transfer of matter Slower in gases due to particles colliding less often

Conduction Conducts thermal energy well Can be hot or cold Ex: Cu, Al Thermal Conductors Thermal Insulators Conducts thermal energy well Can be hot or cold Ex: Cu, Al Tile vs Wood Conducts thermal energy poorly Can be hot or cold Ex: Air, plastic, wool

Convection Transfer of thermal energy when particles of a fluid move from 1 place to another Hot moves to cold Convection Current- fluid circulates in a loop as it alternatively heats up and cools down Oven, heaters Naturally- ocean currents, weather, molten rock

Radiation Transfer of energy by waves moving through space Heat lamps All objects radiate energy- as temperature increases the rate it radiates energy increases

Conduction, Convection or Radiation Heating?

Thermodynamics Thermodynamics 1st Law of Thermodynamics Study of conversions between thermal energy and other forms of energy James Joule, 1800’s Energy is conserved

Thermodynamics Absolute zero cannot be reached 2nd Law of Thermodynamics 4th Law of Thermodynamics Absolute zero cannot be reached Thermal energy can flow from cold to hot objects ONLY if work is done to the system Heat engine- device converts heat into work Waste heat- thermal energy not converted into heat

Using Heat Ch. 16.3

Refrigerants vaporize and condense over and over again True False Statement Heat engines can be internal or external, but neither are very efficient Hot water, steam and electric, and forced air heating all use conduction and radiation to heat Heat pumps reverse the normal flow of thermal energy, which is hot to cold Refrigerators and air conditioners are cooling systems, that don’t require heat pumps Refrigerants vaporize and condense over and over again

Heat Engines Engine that burns fuel outside the engine External Combustion Engine Internal Combustion Engine Engine that burns fuel outside the engine Steam engine Engine that burns fuel inside the engine Cars

Heating Systems Central Heating Systems Heats many rooms from 1 central location Most use convection to distribute thermal energy

Heating Systems Conduction and radiation using water Hot Water Heating Steam Heating Conduction and radiation using water Conduction and radiation using steam

Heating Systems Conduction and radiation using electrical energy Electric Baseboard Heating Forced Air Heating Conduction and radiation using electrical energy Convection using fans

Cooling Systems Heat pumps Device that reverses the normal flow of thermal energy Circulates refrigerant through tubing Refrigerant- fluid that vaporizes and condenses inside the tubing of a heat pump

Cooling Systems Refrigerators Air Conditioners Transfers thermal energy from the inside to the outside Cools inside, releases hot air