If you're seeing this message, it means we're having trouble loading external resources on our website. Show If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked. A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Chemical reactions are an integral part of technology, of culture, and indeed of life itself. An exothermic reaction is a chemical reaction that releases energy by light or heat. It is the opposite of an endothermic reaction. Expressed in a chemical equation: reactants → products + energy. This exercise will allow you to understand chemical reactions, explain what happens during an endothermic reaction, explain the role of a catalyst and make both quantitative and qualitative scientific observations. Materials
How It WorksCaution: Hydrogen peroxide can irritate skin and eyes. Wear goggles and gloves.
Time Initial 1 min 2 min 3 min 4 min 5 min Temperaturę How does it work? The foam you made is special because each tiny foam bubble is filled with oxygen. The yeast acted as a catalyst (a helper) to remove the oxygen from the hydrogen peroxide. Since it did this very fast, it created lots and lots of bubbles This molecule, and others like it, is so explosive because it contains both carbon and hydrogen, and oxygen and nitrogen within its molecular structure. So, in a way, the explosive decomposition of TNT can be considered as a more extreme case of combustion, where the oxidant (the nitro groups) is bound directly to the fuel (toluene).During the manufacture of a chemical, raw materials react together to give the product. Such a chemical process often releases energy, in the form of heat, and the reaction is described as exothermic. A reaction may be exothermic even if you have to heat the reaction mass initially to get the reaction started. Chemical reaction hazards principally arise from:
There are other hazards associated with chemical manufacturing - those arising from handling toxic or flammable chemicals and general hazards such as noise or working at heights. These are covered elsewhere. An exothermic reaction can lead to thermal runaway, which begins when the heat produced by the reaction exceeds the heat removed (see here for factors affecting heat production and removal). The surplus heat raises the temperature of the reaction mass, which causes the rate of reaction to increase. This in turn accelerates the rate of heat production. An approximate rule of thumb suggests that reaction rate and hence the rate of heat generation doubles with every 10 oC rise in temperature. Thermal runaway can occur because, as the temperature increases, the rate at which heat is removed increases linearly but the rate at which heat is produced increases exponentially. This is shown in the Figure. Click here for more discussion on heat transfer in chemical reaction. LAUNCH. Highly exothermic chemical reactions are needed to thrust spacecraft into the air. White plumes following the craft are reaction product gases dispersing aluminum oxide. We can all appreciate that water does not spontaneously boil at room temperature; instead we must heat it. Because we must add heat, boiling water is a process that chemists call endothermic. Clearly, if some processes require heat, others must give off heat when they take place. These are known as exothermic. For purposes of this discussion, processes that require or give off heat will be limited to changes of state, known as phase changes, and changes in chemical constitution, or chemical reactions. Changes of state involve a solid melting, a liquid freezing, a liquid boiling or a gas condensing. When steam, which is gaseous water, condenses, heat is released. Likewise when liquid water freezes, heat is given off. In fact heat must be continually removed from the freezing water or the freezing process will stop. Our experience makes it easy for us to realize that to boil water or any liquid and thereby convert into a gas, heat is required and the process is endothermic. It is less intuitive to grasp that when a gas condenses to a liquid, heat is given off and the process is exothermic. Perhaps it is easier to explain an exothermic phase change using the following argument. Liquid water had to have energy put into it to become steam, and that energy is not lost. Instead, it is retained by the gaseous water molecules. When these molecules condense to form liquid water again, the energy put into the system must be released. And this stored energy is let out as exothermic heat. The same argument can be made for the process of freezing: energy is put into a liquid during melting, so freezing the liquid into a solid again returns that energy to the surroundings. Like phase changes, chemical reactions can occur with the application or release of heat. Those that require heat to occur are described as endothermic, and those that release heat as exothermic. Although we are generally quite familiar with endothermic phase changes, we are probably even more familiar with exothermic chemical reactions: Almost everyone has experienced the warmth of a fireplace or campfire. Burning wood provides heat through the exothermic chemical reaction of oxygen (O) with cellulose (C6H10O5), the major chemical component of wood, to produce carbon dioxide (CO2), steam (H2O) and heat. The chemical reaction describing the process is C6H10O5 + 6O2 = 6CO2 + 5H2O + heat. In today's space age, probably everyone has seen a rocket launch on television or, if lucky, in person. What powers those rockets are highly exothermic chemical reactions. One rocket fuel uses a mixture of solid ammonium perchlorate (NH4ClO4) and aluminum metal (Al) to produce a solid aluminum oxide, hydrochloric acid gas, dinitrogen gas, steam and heat: The chemical reaction can be described as 6NH4ClO4 + 10Al = 5Al2O3 + 6HCl + 3N2 + 9H2O + heat. The great billows of white clouds seen behind launched rockets are really the product gases dispersing the white aluminum oxide powder. Where is the exothermic heat energy coming from? The heat comes from the energy stored in the chemical bonds of the reactant molecules--which is greater than the energy stored in the chemical bonds of product molecules. In endothermic chemical reactions, the situation is reversed: more chemical energy is stored in the bonds of the product molecules than in the bonds of the reactant molecules. Which process is an exothermic process?An exothermic process releases heat, causing the temperature of the immediate surroundings to rise. An endothermic process absorbs heat and cools the surroundings.”
Which of the reactions are exothermic reactions?All combustion reactions are exothermic reactions. During combustion, a substance burns as it combines with oxygen, releasing energy in the form of heat and light.
Which is the process of rapid exothermic reaction?Combustion is defined as a rapid exothermic reaction that liberates substantial energy as heat and flames as combustion reactions with the ability to propagate through a suitable medium.
What is an exothermic reaction called?What is an Exothermic Reaction? A reaction that is chemical in nature and is characterized by the release of energy in the form of heat or light is called an exothermic reaction. Matching a light using a matchstick is one example of this type of reaction where the release is in the form of both heat and light.
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