Effects of Heat


Temperature and Heat I - Concepts
Class - 7th ISO Subjects
 
 
Concept Explanation
 

Effects of Heat

 Effects of heat:

  •  Heat can change the state from Solid to liquid and From Liquid to gas.
  •  Heat can burn things which is a chemical change.
  •  Excessive Heat kills the organisms.
  • Heat Causes Expansion:

    When we heat a substance the energy of the molecules increases, they move away a bit more hence they occupy more space. In liquids molecules move more freely than in solids, when they are heated their movements increases more than in solids. A liquid expands more than solid. Similarly, gases expand more than liquids.

    Expansion in everyday life:

  • The floor is laid out in rectangular pieces, sometime glass is placed between them to allow expansion.
  • Gaps are left between lengths of railway tracks to allow expansion in summers.
  • Gaps are left in the steel structure of bridges to allow expansion. Sometimes they are made to rest on rollers, so that they do not bend on expansion
  • Electric wire between poles sag during summer and become tight in winter because of expansion due to heat.
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    Sample Questions
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    Question : 1

    Which of the following are correct ?

    (a) Heat can change the state from solid to liquid and from liquid to gas.

    (b) Gaps are left between lengths of railway tracks to allow expansion in summers.

    (c)  If rails are fixed tightly, leaving no space for expansion or contraction, they will bend outward in summer. 

     

    Right Option : D
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    Question : 2

    Heat can change the state from Solid to ______________________ .

    Right Option : B
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    Explanation
    Question : 3

    Which of the following are correct ?

    (a) Heat can burn things which is a physical change .

    (b) The temperature rises with heat and as an object is heated it gains energy.

    (c) Excessive heat kills the organisms.

    Right Option : B
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