why do some chemical reactions produce a gain or loss of heat?
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A reaction which gives out heat is known as 'exothermic'.\n\nhttp://en.wikipedia.org/wiki/Exothermic\nhttp://en.wikipedia.org/wiki/Exothermic_reaction\n\nA reaction which seems to absorb heat is known as 'Endothermic'\n\nhttp://en.wikipedia.org/wiki/Endothermic\nhttp://en.wikipedia.org/wiki/Endothermic_reaction
799142
Hi Kitty,\nHere is what, I think, you need.\n\nExothermic, dH < 0, Entropy increases (dS > 0), Reaction is spontaneous and dG < 0\n\nExothermic, dH < 0, Entropy decreases (dS < 0), Reaction is spontaneous only at low temps, if |T dS| < |dH|\n\nEndothermic, dH > 0, Entropy increases (dS > 0), Reaction is spontaneous only  at high temps, if T dS > dH\n\nEndothermic, dH > 0, Entropy decreases (dS < 0), Reaction is not spontaneous, dG > 0
866663
B\n\nStrong bonds requires more energy to break and therefore releases more energy when formed.\n\nSo when enthalpy(heat) is lowered you need something that eats more energy than it creates.
908077
A high temperature will only favour those reactions which are endothermic. To be spontaneous, endothermic reactions require there to be an increase in entropy. You can understand this from the Gibbs Free Energy equation deltaG = deltaH - TdeltaS.  deltaG will tend to become negative as T increases.\nHowever, all reactions proceed faster with an increase in temperature, since a greater proportion of molecules have the minimum energy required to react - the activation energy.\nA low temperature will favour exothermic reactions, and will slow down all reactions.\n\nI do think that the question you are trying to answer is not a particularly good one.
381272
Would you like to qualify that question with something?\nFor example, what material can absorb heat with the smallest increase in temperature.\n\nHeat is a form of energy.  Temperature is the measure of the average kinetic energy of the molecules of a substance.\nAll materials will absorb heat (energy) and their temperature will increase.  How much their temperature increases when a given material absorbs a given amount of heat depends on its specific heat.\nThe specific heat of a material lets up know how much a substance's temperature will increase after abosorbing a given amount of energy.\n\nThe change in temperature of substance experiences can be calculates using the following,\nQ = m*c*(delta T)\nWhere Q is the heat energy, m is the mass of the object, c is the specific heat, and (delta T) is the change in temperature.\n\nA low specific heat means the material will experience a larger increase in temperature (all other things being constant) than a material with a higher specific heat.\n\nThe specific heat of all materials vary.\nAs a general rule, metals tend to have low specific heats and gasses tend to have higher specific heats (there is a reason for this, but it is beyond this answer's scope), but this is not always the case.\n\nWater for example has a pretty high specific heat at about 4.186 J/g degree C (or to simplify, 1 calorie).  By comparison, lead metal has a specific heat of only  1.28 J/g C.\nThis means that the temperature of 1 gram of water will increase by 1 degree C when it absorbs 4.186 Joules of energy.  Likewise, when water cools 1 degree C, it releases 4.186 J of energy.
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Heat is generated through inefficient energy reactions in our body.\n\nAs you may remember from physics class, no reaction is 100% efficient - for example: In a light bulb, not all of the electrical energy in converted into light; some is converted into heat.\n\nThe same is true of our cells, and a some of our energy is released as heat (instead of what is intended!) Muscle movement is especially inefficient, with a great deal of the energy used for muscle cell contraction given off as heat. This is why you get hot when you do exercise!!
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Basically what Le Chatelier's Principle is trying to say is that if a system in equilibrium experiences a change, then it will try and counteract that change.\n\nIn this case, the excess heat is the change experienced. To counteract the excess heat, some of it must be absorbed. Thus, the endothermic reaction in which heat is absorbed will occur at a higher rate than the other reaction. \n\nThe endothermic reaction is the forward reaction. (Equilibrium shifts to the right.) Thus, more N2O4 will be converted to NO2 than the other way round, resulting in less brown-coloured N2O4 molecules in the system. Therefore, the intensity of the colour will decrease.\n\n:) hope you find this useful!
521974
Briefly,\na. The equilibrium constant is constant for a particular reaction, hence when more reagent is added, more products are formed. (Equilibrium constant is (product of conc of products/product of concentration of reactants)\n\nb. Each time reacting species collide, they might not have the right orientation or sufficient energy and hence reaction does not always occur.\n\nc. Increasing the temperature by 10 C nearly doubles the rate of a reaction. This is because the fraction of reacting molecules possessing energy higher than the activation energy increases exponentially with rise in temperature. Also the speed of the molecules increases.
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a) the hydration energy is greater because the temp decreases. When you go from a low potential energy substance to a high potential energy substance the temp of solution will decrease.\n\nb) the solubilty will increase because energy is on the reactant side of the equation. (the reaction is endothermic and requires energy to occur)
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An Endo-Thermic reaction takes in heat and the Exo-thermic one gives off heat.\n\nExemples:\n\nExothermic processes         \nmaking ice cubes              \nrusting iron                  \n\nEndothermic processes \nmelting ice cubes \ncooking an egg
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Any chemical reaction is based on a flow of energy.  Provide more energy and you can then make the reaction faster, as the energy is more abundant to allow the compounds to react, and each molecule will then get to the proper energy level required to react at a faster rate.
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Yes, provided the conditions are right. For example if the reaction\n\nA + B -> c + d\n\nis exothermic, the reaction in reverse will be endothermic, i.e. you will have to supply the heat.
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If you are talking about heat energy then it's called an exothermic reaction.\n\nEndothermic reactions are the ones that absorb heat (i.e. they seem to cool things)
316710
well energy is used only in the beginning to start the reaction. otherwise an exothermic reaction will give out tremendous amount of heat energy.
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In chemistry, an exothermic reaction is one that releases heat. It is the opposite of an endothermic reaction. Expressed in a chemical equation:\n   reactants -->product + energy\n\nWhen using a calorimeter, the change in heat of the calorimeter is equal to the opposite of the change in heat of the system. This means that when the solution in which the reaction is taking place gains heat, the reaction is exothermic.\n\nIn an exothermic reaction the total energy absorbed in bond breaking is less than the total energy released in bond making.\n\nThe absolute amount of energy in a chemical system is extremely difficult to measure or calculate. The enthalpy change, ΔH, of a chemical reaction is much easier to measure and calculate. A bomb calorimeter is very suitable for measuring the energy change, ΔH, of a combustion reaction. Measured and calculated ΔH values are related to bond energies by:\n\nΔH = energy used in bond breaking reactions - energy released in bond making products.\n\nFor an exothermic reaction, this gives a negative value for ΔH as a larger value is subtracted from a smaller value. For example, when hydrogen burns:\n\n\nIn Chemistry an endothermic reaction is one in which the products have more energy than the reactants, and thus a net input of energy, usually in the form of heat, is required. Endothermic reactions are often described as reactions that "feel cold", and contrast with exothermic reactions, in which heat is released.\n\nAlthough the process of bond breaking amongst reactants in a chemical process requires an initial input of energy (the activation energy), in the case of an endothermic reaction, the energy released when bonds are formed to create reactants is less than that required to break the bonds in the products; bonding electrons in the products are therefore at a higher energy than the reactants. Heat energy from the material surrounding the reactants is usually what breaks their bonds, so as heat energy is transferred from the surroundings to the reactants, the surroundings get colder. This is often summarized in a chemical equation as follows:\n\nReactants + Energy → Products
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A reaction tends to be spontaneous if  it causes an increase in the entropy of the system, and/or a decrease in the enthalpy of the system \n\nBoth reactions are endothermic (increase in enthalpy) becuase of positive delta H values.\nBoth have an increase in entropy (positive delta S value for the first one, production of a gas for the second)\n\nSo I'd say statements ll and lll are true.
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Thermodynamics states that heat is a "by product" of a chemical reaction.  So when chemical bonds are broken or made they require energy.  And since energy cannot be completely conserved in an open system (ie the cell) it is inevitable that heat will be produced.  Since the mitochondria is the "energy factory" of the cell and most of the chemical bonds are made in the form of ATP it would make sense that most of the heat is generated in the place where chemical bonds are made and broken.  So the direct answer to your question is, the chemical reactions that occur in the mitochondira cause heat to be generated.