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Temperature and Thermal Energy

Temperature and Thermal Energy. Chapter 12 - 47,48,52,53,57,61,63,71 . Kinetic Molecular Theory. Theory based on the assumption that matter is made up of many tiny particles in constant motion. Hot bodies have more particles moving faster than cold bodies. Thermal Energy.

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Temperature and Thermal Energy

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  1. Temperature and Thermal Energy Chapter 12 - 47,48,52,53,57,61,63,71

  2. Kinetic Molecular Theory • Theory based on the assumption that matter is made up of many tiny particles in constant motion. • Hot bodies have more particles moving faster than cold bodies

  3. Thermal Energy • The sum of the internal kinetic and potential energies of an object. • All energies flow from levels of high energy concentration to low.

  4. Transfer of Thermal Energy • Conduction • Most common in solids • The transfer of kinetic energy when the particles of an object collide. • Convection • The movement of fluids/gases caused by their different densities at different temperatures.

  5. Transfer of Thermal Energy • Radiation • DOES NOT REQUIRE THE PRESENCE OF MATTER. • Thermal energy transferred in the form of electromagnetic waves.

  6. Temperature • The measure of how hot an object is. • Thermal Equilibrium • When two bodies have equal temperatures • When the flow of energy from the 1st object to the 2nd is equal to the flow of energy from the 2nd to the 1st.

  7. Temperature Scales • Fahrenheit • (°Cx1.8)+32 = F • Celsius • Based on the properties of WATER • 0=freezing point of WATER • 100=boiling point of WATER • Kelvin • Absolute Temperature scale

  8. Kelvin • Absolute Zero • 0 Kelvin is the lowest temperature possible. • Not truly possible to be obtained. • Based on the same increments as Celsius • 0 Kelvin = -273 Celsius

  9. Convert 72 oF to oC • C = 5/9 (F-32) • C = 5/9 (72-32) = 22oC • Convert -10 oC to oF • F = 9/5 C + 32 • F = 9/5(-10) + 32 = 14oF

  10. Celsius to Kelvin: T = Tc + 273.15 Problem: 1. The lowest outdoor temperature ever recorded on Earth is -128.6 o F., recorded at Vostok Station, Antarctica, in 1983. What is this temperature on the Celsius and Kelvin scales? Answers: -89.22oC, 183.93 K

  11. Heat • The energy that flows as a result of a difference in temperature. • Represented by the letter Q • Specific Heat • The amount of energy that must be added to raise the temperature of a unit mass one temperature unit. • Represented by the letter C

  12. Specific Heat example • 903 J must be added to 1 kg of Aluminum to raise the temp 1 Kelvin. • C=903 J/kg·K • Q=mCΔT • Q=Heat absorbed/given off • C=Specific heat of material • ΔT=Change in Temperature

  13. See table 12-1 on page 318 Find the amount of heat needed to change the temperature of 5.0 g of liquid water from 8.0oC to 100oC. Q = mcDt = .005kg(4186 j/kgoC) (92oC) = 1.9 x 103 j Again, specific heat is the amount of heat necessary to change one kg of a substance 1 degree Celsius or Kelvin.

  14. When you turn on the hot water to wash dishes, the water pipes have to heat up. How much heat is absorbed by a copper water pipe with a mass of 2.3 kg when its temperature is raised from 20.0oC to 80.0oC? • Q = mcDt • Q = (2.3kg)(390J/kgoC)(60.0oC) • Q = 53820 J or 5.4x104J

  15. 12/4b

  16. Thermodynamics • Explores the properties of thermal energy • Melting Point • Point where internal energy is great enough for the bonding forces to no longer be able to hold particles together. • Particles gain ability to move past one another.

  17. Heat of Fusion • Heat of Fusion • Energy needed to melt 1 kg of a substance. • Measured in units J/kg • Heat of Fusion for water is 3.34x105J/kg. • Means that 1kg of ice needs 3.34x105 Joules of energy to be added to completely turn into water. • ICE 3.34x105J WATER • Added energy changes the state BUT not temperature. • Q=mHf

  18. Boiling Point • Boiling Point • The change of liquid state to a vapor or gaseous state. • Does not change temperature. • Heat of Vaporization • The amount of thermal energy needed to vaporize one kg of a liquid • For water 2.26x106J/kg • Means that 1kg of water needs 2.26x106J/kg of energy to be added to completely turn into water vapor. • Q=mHV

  19. Changes of state

  20. Laws of Thermodynamics • First law of thermodynamics • The total increase in the thermal energy of a system is the sum of the work done on it and the heat added to it. • ΔU=Q-W • U=Total Thermal energy • Q=heat added • W=work done • The change in thermal energy of an object is equal to the heat added to the object minus the work done by the object.

  21. Second law of thermodynamics • Natural processes go in a direction that increases the total entropy of the universe.

  22. Laws of Thermodynamics • Entropy • A measure of disorder in a system • The ratio of heat added to temperature • For example, Gasoline molecules are in a state of relative order. When burned in an engine, bonds are broken, they go kinda crazy, and disorder is increased as is entropy.

  23. Laws of Thermodynamics • Entropy • ΔS=Q/T • S=entopy • Q=heat added • T=temp in kelvin • The change in entropy of an object is equal to the heat added to the object divided by the temp of the object in kelvins • http://www.youtube.com/watch?v=ZsY4WcQOrfk

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