Effects of Heat


 
 
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.
  • Temperature Rises With Heat:

    As an object is heated it gains energy. The kinetic energy of the molecules increases. This increase in energy of the molecules increases the temperature of the object.  

  • An iron rim is heated before being fitted onto wooden wheels: The iron rim is made slightly smaller than the diameter of the wooden wheel. The rim is heated and this hot iron rim is then placed on wooden wheel and cooled by pouring water over it. On cooling, the iron rim contracts and holds the wheel firmly.
  • Riveting of metal plates: A red-hot rivet is passed through the holes in the two plates/sheets.While still red hot it is hammered nearly flat. When the rivet cools down, it contracts, and pulls the two plates together very firmly.
  • To remove a stuck stopper or cap from a bottle: A metal cap stuck on a glass bottle/stuck stopper can be removed from bottle by pouring hot water on cap/neck of the bottle. When hot water is poured over the cap/neck of the bottle, it expands and cap/stopper gets loosened and can be removed easily.
  • Laying of rail tracks: If rails are fixed tightly, leaving no space for expansion or contraction, these will bend outward in summer. It will result in the derailment of train. To avoid such a situation, small gaps are left in between the rails.
  • Laying of telephone and electric transmission wires: When the telephone or telegraph wires are laid in summer they are kept slightly loose so as to allow for contraction in winter. Similarly, if they are laid in winter they are kept very tight so as to allow expansion during summer.
  • Laying of cement floor: Cement floor is laid in small blocks leaving a very small space in between the blocks to allow the expansion and do not crack the floor during the expansion in summer.
  • Illustration: When ice is added to water in a glass, why do we feel cold to touch the glass?

    Solution: Heat flows from a hot body to cold body. Heat flows out of the glass into the ice. Thus the glass loses heat and hence we feel it cold.

    Illustration: An empty bottle is closed tightly with a cork and then heated. After some time the cork shoots out from the mouth of the bottle. What could be the reason?

    Solution: When the bottle is heated, the air in it also gets heated and air expands more. Hence it exerts a force on the stopper and causes it to shoot out of the bottle.

    Sample Questions
    (More Questions for each concept available in Login)
    Question : 1

    In the transmission of electricity  ______________________ between poles sag during summer and become tight in winter because of expansion due to heat.

    Right Option : C
    View Explanation
    Explanation
    Question : 2

    Heat always flows _______________ .

    Right Option : B
    View Explanation
    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
    View Explanation
    Explanation
    Chapters
    Cytology
    Classifucation Of Plants
    Structural Composition Of Plants
    Nutrition In Plants, Harmones And Plant Disease
    Ecosystem
    Classification In Animals
    Nutrition In Animals
    Human Digestive System
    Human Respiratory System
    Human Skeleton System
    Human Excretory System
    Human Nervous System
    Human Circulatory System
    Human Endocrine System
    Human Reproductive System
    Genetics
    Human Diseases
    States Of Matter
    Metals And Non Metals
    Acid Bases And Salts
    Periodic Classification
    Fuel, Combustion And Flame
    Environmental Chemistry
    Rest And Motion
    Work Power And Energy
    Gravitation
    Pressure And Its Effects
    Simple Harmonic Motion
    Sound and Waves
    Heat And Temperature
    Light - Reflection
    Electricity And Magnetism
    Modern Physics
    Force And The Laws Of Motion
    Light - Refraction
    Dispersion And Human Eye
    Magnetic Effect Of Electric Current
    Atom And Molecule
    Pre-Historic Period
    Indus Valley Civilization
    Vedic Civilization
    Religious Reform Movement
    The Early Kingdoms
    The Mauryan Empire
    Post Mauryan Period
    The Age Of The Guptas
    Post Gupta Era
    Age of Rajput
    Khilji Dynasty
    Slave Dynasty
    Tughlaq and Sayyid Dynasty
    Vijaynagar Empire And Bahamani Kingdom
    Mughal Empire And Beyond
    Lodhi Dynasty
    Cholas, Chalukyas and Pallavas
    Arab Invasions
    Bhakti and Sufi Movement
    Rise of Sikhs, Jats and Marathas
    Administrative Structure of Delhi Sultanate
    Architecture During Medivial India
    Advent Of The Europeans
    Post Mughal Period
    Rise of New States in 18th Century
    Growth of British Paramountacy
    Socio Religious Reforms
    Constitutional Development of India
    Indian Struggle Against British Rule
    The Revolt Of 1857
    Education Under British Rule
    Role of Press in Freedom Struggle
    First Phase of National Movement
    Second Phase of National Movement
    Third Phase of National Movement
    Constitutional Development in India
    Constituent Assembly
    Union And Its Territory
    Structure of Indian Constitution
    Fundamental Rights and Duties
    The Union Executive
    The Union Legislature
    Constitutional Amendments and Provisions
    Judiciary In India
    Emergency Provisions
    Center - State Relations
    The State Executive
    The State Legislature
    Election Commission Of India
    Constitutional Organisation
    Non-Constitutional Organisation
    Local Self Goverment
    India - Size And Location
    Geological History Of India
    The Physical Features Of India
    Climate Of India
    Soils In India
    Natural Vegetation
    Windlife Conservation In India
    Drainage System of India
    Irrigation System Of India
    Agriculture In India
    Livestock And Fisheries In India
    Minerals And Energy Resources In India
    Means Of Transport In India
    Major Industries In India
    Tribes of India
    Census of India 2011
    Music
    Dance
    Theatre
    Pantings
    Art, Architecture & Culture of India
    Bio-Diversity
    Earth And Its Structure
    Land Rock And Soil
    Atmosphere, Climate And Weather
    Oceanography
    Human And Regional Geography
    Economic Growth And Development
    Sectors Of Indian Economy
    Economic Planning Of India
    Fiscal And Monetary Policy In India
    Infrastructure In India
    Effects Of British Rule On Indian Economy
    National Income
    Banking System In India
    Poverty And Unemployment
    Inflation And Trade Cycles
    Major Institutions
    Environmental Studies
    Chemistry In Everyday Life
    Units And Dimensions
    Tissues In Organism
    Content / Category
    Class / Course
     
     


    Students / Parents Reviews [20]