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Changes caused by heating

 

Changes in matter ] Importance of chemical reactions ] Chemical Reactions ] On-line practice ]

  1. Physical change
  • Heating can cause matter to change its state
  1. Expansion and contraction
  • Usually an object expands when it is heated.  Expansion refers to an increase in volume of the substance.
  • When an object is cooled, it usually contracts.  Contraction refers to a decrease in volume.
  1. Combination
  • Combination is a chemical change in which two or more substances combine to form a new substance.
  • Example : Sodium + Chlorine --> Sodium chloride
  • The new substance that is formed has very different properties from its constituents.
  1. Thermal Decomposition
  • Thermal decomposition is a process whereby a substance breaks down into two or more simpler substances by the effect of heat.
    • Substance A --> Substance B + Substance C
    • Example :  Calcium carbonate --> Calcium oxide + Carbon dioxide
  • Some substances decompose on heating
  1. Combustion
  • Combustion is the process whereby a substance combines with oxygen gas to form a new substance.
  • Usually, combustion is accompanied by the release of heat energy and sometimes light energy.
  • Example :  Carbon + Oxygen --> Carbon dioxide

 

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