What type of chemical reaction occurs when a substance is exposed to heat?
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it will speed up the reaction since the heat rises the temperature.\nit will also decompose a compound to its elements--decomposition reaction.
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when in a chemical reaction
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Fire is the result of a combustion chemical reaction in which a hydrocarbon (a compound containing carbon and hydrogen) is reacted with oxygen forming carbon dioxide and water.  This reaction releases a lot of energy in the form of thermal (heat) radiation which is the result of fire.\n\nNote that there are other compounds which react with oxygen to release much energy and form oxides, but they're not relevant with respect to water.\n\nIce is water and not a hydrocarbon so it can not catch on fire.
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1.  Heat speeds up a reaction by increasing vibrations and energy of the reactants.\n\n2.  Concentration speeds us a reaction by making more reactants available in a unit volume.\n\n3.  Catylists speed up a reaction (without being used up) by allowing reactants to come into closer proximity.\n\n4.  Increased surface area (by grinding, etc.) speeds up reactions by making more reactants exposed to reaction.
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GO to wikipedia.com and type in chemical reaction.  That is kind of a tough definition, so I will help to break it down a little for you.  Basically, you got something, and it changes into a whole new a different thing.  That is a chemical reaction.  It could be 2 things coming together to make 1 thing, or vice versa.  Or two things could lead to 2 new things.  The most important part of a chemical reaction is that substances change to NEW substances that have serperate properties and characteristics from the original.\nOn wikipedia there is a link to an IUPAC definition.  IUPAC is pretty much in charge of defining stuff in chemistry, so their definition is the one you're looking for, however, it might be a little complicated.  If this didn't help, maybe you should repost your question.
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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)
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During a chemical reaction, existing bonds are broken, atoms are rearranged and new bonds are formed.
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In physics, heat is defined as energy in transit. Generally, heat is a form of energy associated with the motion of atoms, molecules and other particles which comprise matter. Heat can be created by chemical reactions (such as burning), nuclear reactions (such as fusion taking place inside the Sun), electromagnetic dissipation (as in electric stoves), or mechanical dissipation (such as friction). Heat can be transferred between objects by radiation, conduction and convection. Temperature, defined as the measure of an object to spontaneously give up energy, is used to indicate the level of elementary motion associated with heat. Heat can only be transferred between objects, or areas within an object, with different temperatures.
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Specific heat does not apply to reactions, only actual chemicals.  You are probably thinking of the heat of reaction, or enthalpy.  The change in enthalpy of a reaction (written as delta H, delta as the Greek letter that looks like a little triangle) flips its sign when the reaction is run in the reverse direction.  So a positive delta H value becomes negative when the reaction is run in reverse direction, and a negative delta H value becomes positive.
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The sign there is a chemical reaction is the fact there is heat being released.  Evidently, the reactant have more energy, because they are able to release that energy in the form of heat.
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Most reactions are exothermic.\nExamples are\n\n1) Combustion of methane (natural gas).\n\n2) Neutralisation of dilute hydrochloric acid and dilute sodium hydroxide.\n\n3) Adding concentrated sulphuric acid to water is highly exothermic\n(gives out a lot of heat).\n\n4) Adding water to anhydrous copper(II) sulphate is exothermic.\nAnhydrous copper(II) sulphate is white.\nAnhydrous is pronounced "an-high-drus"\nAnhydrous means "without water".\n\nAnhydrous copper(II) sulphate is copper(II) sulphate which is completely dry.\nWhen water is added to it, it turns into the familiar hydrated blue crystals.\nHydrated is pronounced "high-dray-tid", it means 'with water'.\nThis is used as a test for water.\n\nIf blue (hydrated) copper(II) sulphate crystals are heated,\nan endothermic reaction occurs, they lose their water,\nturn white and become anhydrous copper(II) sulphate crystals again.\nThe reaction is reversible.\nBlue copper(II) sulphate crystals will also turn white in the presence of  concentrated sulphuric acid.\n\n \n\nFew reactions are endothermic.\nExamples are\n\n1) Photosynthesis.\nChlorophyll is a very clever catalyst,\nwhich allows plants to make sugar from carbon dioxide in the air.\nThe energy needed for the reaction comes from sunlight.\n\n2) The reaction of ethanoic acid with sodium carbonate.\n\n3) Dissolving some salts in water is an endothermic process.\nPotassium chloride and ammonium nitrate\nboth take in energy when they dissolve.\nIf you put a thermometer in the solution as they are dissolving,\nyou will see that the temperature drops.\n\n4) Melting, boiling and evaporation\nare all endothermic processes (not reactions).
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Physical\n\nA chemical change is a change in molecular composition. For example: When you mix baking soda and vinegar, it ceases to be simply soda and vinegar. A chemical reaction takes place.\n\nA physical change is a change in physical property. For example: The irons heating element is activated, causing the metal to warm up. It doesn't change to any other form of metal, nor does its structure differ afterwards. It mearly changes in physical temperature.
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Friction, Heat, Acid.
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A solid that is formed by a chemical reaction.
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All of the above.\n\nActually even Magnetism is affected by heat.  Heat a magnet and it will lose its magnetism.\n\nChemical composition will also change.
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the water is relesed as vapor from the liquid when the liquid is heated. Water changes phase and becomes gas, its called evaporation.
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strictly speaking, substances undergo combustion in the presence of oxygen and 'burn' would not be precise. \nhowever answering the question, oxygen is an oxidising substance and hence it is able to oxidise the organic subs. and usually converting them into carbon di oxide and water, and this is accompanied by the release of energy in the form of heat