Biophysical? Does the room feel colder?

  1. Let's say you're in a room that's 100 degrees Farenheight. This is an airtight room (you won't suffocate.). Without changing the temperature of the room, a chemical reaction begins (I don't know which chemicals this would be). This chemical reaction pulls in heat and stores them in its bonds. Does the room feel colder?
    I'd like to thank anyone who answers a ton.
     
  2. jcsd
  3. davenn

    davenn 3,977
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    hi there Alltimehigh

    welcome to PF :smile:

    any reaction that takes in heat is called an endothermic reaction
    its found in examples of ....
    Melting ice, Photosynthesis in plants, Alcohol that's evaporating, to name several
    the heat isn't stored as such, rather it is just used to "fuel" the reaction

    Yes it should cause a temp drop in the room .... say as the ice melts to water. There would come a point where the water temp and the room temp would reach equilibrium.
    With a person in the room, that may take longer or be a little more difficult as that person would still be continuing to radiate heat

    Hope that helps

    Dave
     
  4. davenn

    davenn 3,977
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    LOl Dale your quick answer beat mine

    D
     
  5. Thanks. So the movement of the atoms is replaced by the holding of the bonds together? That's what I'm getting. Anybody want to post some math for this?
     
  6. Not necessarily. Davenn gave a good example, ice melting, where the result is a disruption of hydrogen bonds. The thermal energy is required to break the bonds.
     
  7. but I thought heat cannot be created nor destroyed. Does it turn into matter?
     
  8. Drakkith

    Staff: Mentor

    It wasn't destroyed, it was transferred to the material. The bonds within the ice broke precisely because the ice gained thermal energy which disrupted the bonds between the water molecules.
     
  9. davenn

    davenn 3,977
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    you are misquoting

    its energy that can neither be created nor destroyed ... it just gets transferred

    Dave
     
  10. D H

    Staff: Mentor

    You meant temperature, not heat. Heat, as used by physicists, is not a conserved quantity. It's not even a state variable. (Temperature on the other hand is a state variable.) Heat is a measure of thermal energy that is transferred due to some thermodynamic process. Heat, like work, is a process variable.

    Temperature is not a conserved quantity, either. Energy is. Temperature is one form of energy. Mass is another. There are all kinds of different forms of energy.

    To conserve energy, chemical reactions inevitably involve a change in mass. However, the change is very, very small. It's not measurable unless you have an extremely accurate equipment and control the experiment.

    A typical chemical reaction consumes or releases 100 kcal of energy per mole of reactants. Dividing by the square of the speed of light yields a mass change of 4.7 nanograms per mole. That change is so very small that you can safely treat it as zero and say that mass is conserved in chemical reactions.
     
  11. There are four concepts here that you need to think about here:

    1) Energy
    2) Thermal energy
    3) Temperature
    4) Heat

    Of these 4, only energy is conserved. Thermal energy can be converted to other forms of energy, such as chemical potential energy, so thermal energy is not conserved. Temperature is a relationship between thermal energy and entropy, it is not conserved. Heat is a transfer of thermal energy between two bodies based on a difference in temperature, so it is not conserved either.

    When you have a room at room temperature with some ice in it the room has a higher temperature than the ice. Due to this temperature difference thermal energy can be transfered from the room to the ice, this is called heat. The thermal energy removed from the room will decrease its temperature. The thermal energy added to the ice will not increase its temperature, but will instead act to break the hydrogen bonds keeping the ice solid, causing melting. The resulting water will have more energy than the ice, although the temperature is the same. Only the total energy would have been conserved.
     
  12. thanks. Totally cleared it up for me. Thanks, again.
     
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