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Thread: Problem!!!!!!!!!!

  1. #1 Problem!!!!!!!!!! 
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    What is the difference between the ability of conduct heat and absorption of heat?
    Are they related?
    If a ability of conduct heat is high,are its absorption of heat is high?
    a black-coloured plastic have a higher absorption of heat, but its ability of conduct is low.....
    How to differentiate them?????
    are wood is a good "heat absorber"?
    -----------------------------------------------------------------------------------------------
    What the properties of ice that makes it suitable to build igloo?
    -----------------------------------------------------------------------------------------------
    Why heat convection(air) will spins the spiral cardboard?


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  3. #2 Re: Problem!!!!!!!!!! 
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    Quote Originally Posted by ~James~
    What is the difference between the ability of conduct heat and absorption of heat?
    Are they related?
    If a ability of conduct heat is high,are its absorption of heat is high?
    a black-coloured plastic have a higher absorption of heat, but its ability of conduct is low.....
    How to differentiate them?????
    are wood is a good "heat absorber"?
    -----------------------------------------------------------------------------------------------
    What the properties of ice that makes it suitable to build igloo?
    -----------------------------------------------------------------------------------------------
    Why heat convection(air) will spins the spiral cardboard?
    I'm. not sure what you're looking for. Maybe the terms "emissivity" and "black body" will help?

    Check this site out as well:

    Spectralcalc Blackbody Calculator

    The calculator will work without a log in if I remember right, and you can get a temporary free membership. There are other good features in the other links of the site that I like.

    As for black plastic... looks are deceiving. It blocks visible light, but it can pass infrared.


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  4. #3  
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    Can anybody help me?
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  5. #4 Re: Problem!!!!!!!!!! 
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    Double Post
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  6. #5 Re: Problem!!!!!!!!!! 
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    Quote Originally Posted by ~James~
    What is the difference between the ability of conduct heat and absorption of heat?
    Are they related?
    If a ability of conduct heat is high,are its absorption of heat is high?
    a black-coloured plastic have a higher absorption of heat, but its ability of conduct is low.....
    How to differentiate them?????
    are wood is a good "heat absorber"?
    -----------------------------------------------------------------------------------------------
    What the properties of ice that makes it suitable to build igloo?
    -----------------------------------------------------------------------------------------------
    Why heat convection(air) will spins the spiral cardboard?


    1/ No they are not necessarily related; absorption and conduction.

    2/ Water, and thus ice, are poor thermal [and electrical] conductors.
    So ice makes a good insulator and thus an igloo paradoxically
    as that may seem

    3/ Heat convection thru air creates molecular upward motion
    as the less dense hot air rises. This will spin a helical cardboard coil
    in a way similar to an airplane foil creating lift.
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  7. #6  
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    They are different properties of matter:
    Specific heat capacity, often shortened to specific heat, is the measure of the heat energy required to increase the temperature of a unit quantity of a substance by unit degree. The term originated primarily through the work of 18th-century physicist Joseph Black who conducted various heat measurements and used the phrase "capacity for heat".[1] More heat energy is required to increase the temperature of a substance with high specific heat capacity than one with low specific heat capacity. For instance, eight times the heat energy is required to increase the temperature of an ingot of magnesium as is required for a lead ingot of the same mass. The specific heat of virtually any substance can be measured, including chemical elements, compounds, alloys, solutions, and composites.

    In metals, thermal conductivity approximately tracks electrical conductivity according to the Wiedemann-Franz law, as freely moving valence electrons transfer not only electric current but also heat energy. However, the general correlation between electrical and thermal conductance does not hold for other materials, due to the increased importance of phonon carriers for heat in non-metals. As shown in the table below, highly electrically conductive silver is less thermally conductive than diamond, which is an electrical insulator.

    Thermal conductivity depends on many properties of a material, notably its structure and temperature. For instance, pure crystalline substances exhibit very different thermal conductivities along different crystal axes, due to differences in phonon coupling along a given crystal axis. Sapphire is a notable example of variable thermal conductivity based on orientation and temperature, with 35 W/(mĚK) along the c-axis and 32 W/(mĚK) along the a-axis.[12]

    Air and other gases are generally good insulators, in the absence of convection. Therefore, many insulating materials function simply by having a large number of gas-filled pockets which prevent large-scale convection. Examples of these include expanded and extruded polystyrene (popularly referred to as "styrofoam") and silica aerogel. Natural, biological insulators such as fur and feathers achieve similar effects by dramatically inhibiting convection of air or water near an animal's skin.

    Light gases, such as hydrogen and helium typically have high thermal conductivity. Dense gases such as xenon and dichlorodifluoromethane have low thermal conductivity. An exception, sulfur hexafluoride, a dense gas, has a relatively high thermal conductivity due to its high heat capacity. Argon, a gas denser than air, is often used in insulated glazing (double paned windows) to improve their insulation characteristics.

    Thermal conductivity is important in building insulation and related fields. However, materials used in such trades are rarely subjected to chemical purity standards. Several construction materials' k values are listed below. These should be considered approximate due to the uncertainties related to material definitions.

    The following table is meant as a small sample of data to illustrate the thermal conductivity of various types of substances. For more complete listings of measured k-values, see the references.

    [edit] List of thermal conductivity values
    Main article: List of thermal conductivities
    This is a list of approximate values of thermal conductivity, k, for some common materials. Please consult the list of thermal conductivities for more accurate values, references and detailed information.

    Material Thermal conductivity
    W/(mĚK)
    Silica Aerogel 0.004 - 0.04
    Air 0.025
    Wood 0.04 - 0.4
    Hollow Fill Fibre Insulation Polartherm 0.042
    Alcohols and oils 0.1 - 0.21
    Polypropylene 0.12 [2]
    Mineral oil 0.138
    Rubber 0.16
    LPG 0.23 - 0.26
    Cement, Portland 0.29
    Epoxy (silica-filled) 0.30
    Epoxy (unfilled) 0.59
    Water (liquid) 0.6
    Thermal grease 0.7 - 3
    Thermal epoxy 1 - 7
    Glass 1.1
    Soil 1.5
    Concrete, stone 1.7
    Ice 2
    Sandstone 2.4
    Stainless steel 12.11 ~ 45.0
    Lead 35.3
    Aluminium 237 (pure)
    120Ś180 (alloys)
    Gold 318
    Copper 401
    Silver 429
    Diamond 900 - 2320
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  8. #7  
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    Thank you!
    but i still have a problem..



    1.are ice absorb heat slowly?
    2.are ice release heat fastly?
    just need answer me yes or no.....
    Thanks!!!!!!!!!!!! :wink:
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  9. #8  
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    Quote Originally Posted by ~James~

    Thank you!
    but i still have a problem..



    1.are ice absorb heat slowly?
    2.are ice release heat fastly?
    just need answer me yes or no.....
    Thanks!!!!!!!!!!!! :wink:
    compared to air in earth yes and no. see how mist happen in shallow river or lake.
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  10. #9  
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    Not sure if anyone touched on this, but heat conductivity affects emissivity and capacity AFAIK. If conductivity is low, then it takes longer for the heat to move to the surface to be emitted. So the object can get hotter before equilibrium is reached.
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

    "Gullibility kills" - Carl Sagan
    "All people know the same truth. Our lives consist of how we chose to distort it." - Harry Block
    "It is the mark of an educated mind to be able to entertain a thought without accepting it." - Aristotle
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  11. #10  
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    Quote Originally Posted by shikigamics
    Quote Originally Posted by ~James~

    Thank you!
    but i still have a problem..



    1.are ice absorb heat slowly?
    2.are ice release heat fastly?
    just need answer me yes or no.....
    Thanks!!!!!!!!!!!! :wink:
    compared to air in earth yes and no. see how mist happen in shallow river or lake.
    I don't know.......Please tell me ...just answer yse or no...
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  12. #11  
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    Who can help me?
    1.Are ice absorb heat slowly?
    2.Are ice release heat fastly?
    3.How a diffusion of matter occur on a solid????
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  13. #12  
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    Quote Originally Posted by ~James~
    Who can help me?
    1.Are ice absorb heat slowly?
    2.Are ice release heat fastly?
    3.How a diffusion of matter occur on a solid????
    for 1 and 2 : http://scienceworld.wolfram.com/phys...cificHeat.html
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  14. #13 Diffusion Equation 
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    The answers to your questions are not trivial.
    It involves the solution to the Diffusion Equation and Fick's Law.
    So look them up and learn about it on your own.

    I believe it was Fourier who first solved the problem which
    was an unsolved issue in physics for a long time.

    Here is a link that might be useful
    http://en.wikipedia.org/wiki/Heat_transfer
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  15. #14  
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    1.ice problem
    just say yes or no...
    :?

    2.we use charcoal or coal in BBQ?
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  16. #15  
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    1.ice problem
    just say yes or no...
    :?

    2.we use charcoal or coal in BBQ?
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  17. #16  
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    1.ice problem
    just say yes or no...
    :?

    2.we use charcoal or coal in BBQ?
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

    "Gullibility kills" - Carl Sagan
    "All people know the same truth. Our lives consist of how we chose to distort it." - Harry Block
    "It is the mark of an educated mind to be able to entertain a thought without accepting it." - Aristotle
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  18. #17  
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    Quote Originally Posted by KALSTER
    1.ice problem
    just say yes or no...
    :?

    2.we use charcoal or coal in BBQ?
    What?
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