thermal physics

• Definition of Heat Capacity, C


  This is the heat energy needed to raise the temperature of a substance by 1 kelvin.
• Definition of Specific Heat Capacity, c

  This is the heat energy needed to raise the temperature of 1kg of a substance by 1 kelvin.
• Formula and Unit of Heat Capacity

  unit: JK-1

  formula: C = Heat Energy / change in temperature

  = E / T
• Formula and Unit of Specific Heat Capacity

  Unit: JKg-1K-1

  Formula : c = Heat Energy / mass x change in temp.

  = E/mT
• Definition of Specific Latent Heat of Fusion, lf

  This is the heat energy required to change 1kg of a solid substance from a solid to a liquid without a change in temperature.
• Specific latent heat of fusion (lf) and specific latent heat of vaporization (lv) are both measured in joules per kilogram (J/kg).
• Definition of specific latent heat of vaporisation, lv


  This is the heat energy required to change 1kg of a liquid to a gas without a change in temperature.
• definition of latent heat

  This is the heat energy that changes the phase/state of a substance.
• thermometric properties of thermometers

  Liquid-in-Glass : volume

  Thermocouple: EMF (electro motive force)

  Constant volume gas: Pressure

  platinum resistance: resistance
• A thermometric property is one which responds to changes in temperature in a proportional relationship.
• Upper fixed point/steam point : This is the temperature of steam above boiling water at 100 degrees C and at standard atmospheric pressure of 1 atmosphere.
• Lower fixed point/ ice point : This is the temperature of pure melting ice at 0 degrees C and at standard atmospheric pressure of 1 atmosphere.
• Thermocouple use : measures extremely high temperatures and responds to rapidly changing temps.

  range : -200 to 1500 degrees C

  or : -250 to 800 degrees C
• Clinical thermometer use: To measure body temperature

  range: 34 - 43 degrees C

  or 35 - 43 degrees C
• Laboratory thermometer- measures boiling and freezing points of water and other substances as well as room temperature.

  range: -10 to 110 degrees C

  OR -20 to 110 degrees C
• Alcohol thermometers- used to measure very low temperatures

  range : 0 to -40 degrees C

  OR 0 to -70 degrees C
• Heat is transferred from a hot object to a cold object by conduction, convection and radiation.
• Heat energy is transferred from a hot object to a cold object until it has been evenly distributed. This point is called thermal equilbrium.
• E = mlf

  E = mc(T)

  E= mlv
• E = IVt for electrical energy
• Describe how air molecules exert pressure on the surface of a balloon.

  Air/gas molecules are in constant random motion because they possess a large amount of kinetic energy.

  The molecules collide with the surface of the balloon and exert a force onto the surface.

  A force is exerted per unit area, and this produces pressure.
• characteristic features of a clinical thermometer:

  Narrow constriction in the tube above the bulb

  limited range of temperatures