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Math Help - BTU calc of heat energy converted from chemical energy

  1. #1
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    BTU calc of heat energy converted from chemical energy

    Gentlemen:

    Please excuse my ignorance on this topic. I need to know how to calculate the BTUs from the chemical engery released in heating peanuts; or nuts in a can of water?
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    Quote Originally Posted by ortizsr
    Gentlemen:

    Please excuse my ignorance on this topic. I need to know how to calculate the BTUs from the chemical engery released in heating peanuts; or nuts in a can of water?
    Maybe if you can provide more information. In physics there is a formula,
    H=m\cdot c\cdot \Delta t
    Where H is heat in calories, q is specific heat and \Delta t is change in temperature. Once you have that you can convert to BTU's because 1\mbox{ BTU }\approx 250\mbox{ calories}
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    Quote Originally Posted by ortizsr
    Gentlemen:

    Please excuse my ignorance on this topic. I need to know how to calculate the BTUs from the chemical engery released in heating peanuts; or nuts in a can of water?
    I'm a tad confused here (my normal state! )

    The comment about heating the peanuts and finding the chemical energy released sounds like you are using some form of a "burn calorimeter" but heating the nuts in a can of water doesn't. What specific experiment are you doing here?

    -Dan
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    Dear Dan:
    Thank you for the response.

    Let me clarify the experiment. Peanuts placed on a needle point stuck to a cork is first heated. Then placed under a large can that has a smaller can containing a quarter cup of water.
    I then measure the change in temperature (F) and compute the BTUs.
    At the moment the following formula is used:
    one BTU = .252 calories = 1 degree change in temperature.

    Is my formula correct or is there a better way??

    respecfully,
    Herman Ortiz
    ortizsr@joimail.com
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    Quote Originally Posted by ortizsr
    Dear Dan:
    Thank you for the response.

    Let me clarify the experiment. Peanuts placed on a needle point stuck to a cork is first heated. Then placed under a large can that has a smaller can containing a quarter cup of water.
    I then measure the change in temperature (F) and compute the BTUs.
    At the moment the following formula is used:
    one BTU = .252 calories = 1 degree change in temperature.

    Is my formula correct or is there a better way??

    respecfully,
    Herman Ortiz
    ortizsr@joimail.com
    I don't think that will help us much in understanding what you are trying to do.

    Can you tell us what you are trying to measure, how you propose to do
    it, and I think we will need a diagram of the apparatus as well.

    RonL
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    Dear RonL:

    Sorry for a lack of clarity in my summary.

    The objective is to compute the BTUs created by measuring the (F) temperature before and after heating a Peanut underneath two cans.
    A small can containing 1/4 cup of water held over a larger empty can (without end caps).

    I determined that one BTU is equal to .252 calories of heat, and this relationship forms the bases of the formula.

    Am I right or is there a better formula??

    How do I enclose a diagram in this reply??

    Respectfully,
    Herman Ortiz
    ortizsr@joimail.com
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    Quote Originally Posted by ortizsr
    Dear RonL:

    Sorry for a lack of clarity in my summary.

    The objective is to compute the BTUs created by measuring the (F) temperature before and after heating a Peanut underneath two cans.
    A small can containing 1/4 cup of water held over a larger empty can (without end caps).

    I determined that one BTU is equal to .252 calories of heat, and this relationship forms the bases of the formula.

    Am I right or is there a better formula??

    How do I enclose a diagram in this reply??

    Respectfully,
    Herman Ortiz
    ortizsr@joimail.com
    A BTU is a British Thermal Unit an archaic unit of energy which is the
    energy required to raise the temperature of 1 pound (yuck) of water by
    1 degree Fahrenheit, when the water is at its maximum density.

    It looks like you are trying to measure the thermal capacity of the peanut
    before and after heating (except normalisation for mass does not seem to
    be involved). Though the exact process still is not clear to me.

    As a personal preference I would use Joules and degrees Celsius for this
    task.

    RonL
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    Quote Originally Posted by ortizsr
    Dear RonL:

    Sorry for a lack of clarity in my summary.

    The objective is to compute the BTUs created by measuring the (F) temperature before and after heating a Peanut underneath two cans.
    A small can containing 1/4 cup of water held over a larger empty can (without end caps).

    I determined that one BTU is equal to .252 calories of heat, and this relationship forms the bases of the formula.

    Am I right or is there a better formula??

    How do I enclose a diagram in this reply??

    Respectfully,
    Herman Ortiz
    ortizsr@joimail.com
    Okay, so if I understand correctly you are trying to measure the heat given off by burning a peanut by measuring the temperature change of a quantity of water sitting over top of the said peanut. (This IS a kind of burn calorimeter, though a low precision one. Theoretically, the burning peanut should be surrounded by insulating material so that any horizontal heat flow is trapped to heat the water bath as well.)

    You sort of have the right formula. (Perhaps you have already taken the following into account. If so, well done, and feel free to ignore me! )
    1. As CaptainBlack said, 1 BTU applies to heating 1 lb of water (at maximum density, ie about 4 degrees C, however this shouldn't change all that much if you are working at a different temperature.) Since you only have 1/4 cup of water, you need to make sure you are multiplying your answer by the correct factor to account for this.

    2. I looked up BTU (I can never remember conversion factors!) and I have that 1 BTU = 252 cal. Could you be speaking of Calories and not calories? (1000 cal = 1 kcal = 1 Cal.)

    Other than that, it sounds good. Find your temperature change, multiply that by your water volume factor and that gives you the number of Calories. Good luck!

    -Dan
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