Chapter 4: Heat and Temperature Summary

Chapter 4: Heat and Temperature Summary


There are three phases of matter: Solid, Liquid and Gases.




Solid Liquid Gas
Shape Definite Indefinite Indefinite
Volume Definite Definite Indefinite
Movement Allowed Vibration Vibration, Rotation and Limited translation Vibration, rotation and translation
Atom/Molecules Stationary and in contact Mostly in contact Mostly not in contact


Molecular Motions

  • Characterized by Kinetic Energy (KE). Temperature is a measurement index for the KE.
  • Illustration
  1. Faster diffusion of gases at high temperature
  2. Expansion and contraction with temperature changes


  • Refers to the internal energy of an object (Average kinetic energy)
  • Measured using thermometer whose functionality depends on thermometric properties e.g., thermostats and bimetallic.
  • Thermometric scales used include Fahrenheit, Celsius and Kelvin.
  • Conversion to either scale from another is as shown;

TF= Fahrenheit to Celsius

TC=Celsius to Fahrenheit

TK= Celsius to Kelvin



  • Internal Energy transferred from one point to another due to differences in temperature or energy form conversion.
  • External energy (E)= Total potential E. + Total Kinetic E. (of an object)
  • Internal E. = Total Kinetic E.
  • Change from external to internal energy results in Temperature increase
  • Specific heat refers to heat energy required to raise the temperature of 1 kg object by one degree Celsius
  • Heat transfer is by conduction, convection or radiation
  • Conduction involves heat transfer in solids through atom collision hence cannot occur in vacuum
  • Convection is heat transfer by bulk movement of hot material such as rising of hot air in natural convection
  • Energy transfer through electromagnetic waves and hence can occur in a vacuum. Temperature determines emission rate, light intensity and radiation type.

Evaporation: involves overcoming of cohesion force by molecules that then escape

Condensation: involves losing of KE by gas molecules that merge to liquid


  • Study of heat and its relationship to mechanical and other energy forms
  • Involves consideration of the system, surroundings and internal energy
  • Laws of thermodynamics

1st Law: Conservation of energy- heat is not lost but is converted from one form to another. Considers internal energy

2nd Law: Comprises three parts;

  1. No heat to work is 100% efficient- some energy is lost.
  2. A cold body requires work to heat hot body.
  3. Entropy of an isolated system always increases


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