exothermic and endothermic reaction (science)
- Created by: maryam_444
- Created on: 29-09-18 11:39
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- exeothermic and endothermic reaction
- Exothermic
- exothermic reaction is when heat is given out to the surroundings
- this is shown In rise in temperature
- for example burning fuel is a great example of exothermic reaction
- this is also called combustion. this gives out a lot of energy
- many oxidation reactions are exothermic. for example adding sodium to water releases energy.
- the reaction releases energy and the sodium moves about on the surface of the water as it oxidised.
- for example burning fuel is a great example of exothermic reaction
- this is shown In rise in temperature
- neutralisation reaction is also exothermic (acid + alkali)
- exothermic reaction is when heat is given out to the surroundings
- Endothermic
- endothermic is when heat is taken in by the suroundings
- this is shown by fall in temperature
- endothermic reactions are much less common than exothermic
- they include the reaction between citric acid and sodium hydrogencarbonate
- thermal decomposition e.g. heating calcium carbonate causes it to decompose into calcium oxide (also called quicklime)
- calcium - CaCOcubed (+heat) - CO2 + CaO = quicklime
- endothermic reactions are used in some sports injury packs. the chemical reaction allows the pack to become instantly cooler without having to put it in the freezer.
- thermal decomposition e.g. heating calcium carbonate causes it to decompose into calcium oxide (also called quicklime)
- they include the reaction between citric acid and sodium hydrogencarbonate
- endothermic is when heat is taken in by the suroundings
- energy transferred can be measured
- the amount of energy released can be measure by a chemical reaction (in solution) by taking the temperature of the reagents, mixing them in a polystyrene cup and the measuring the temperature of the solution at the end.
- materials that should be used in the practical: lid, large beaker, polystyrene cup, cotton wool, thermometer and reaction mixture
- you can reduce the amount of energy loss by putting the polystyrene cup into a beaker of cotton wool to give more insulation of the reactant used.
- also putting a lid on the beaker reduces energy loss by evaporating.
- you can reduce the amount of energy loss by putting the polystyrene cup into a beaker of cotton wool to give more insulation of the reactant used.
- the method works for neutralisation reactions or reactions between metals and acid, or carbonates and acids.
- this method can also be used to investigate what effect variables have on the amount of energy transferred. e.g. the mass or concentration of the reactants used.
- materials that should be used in the practical: lid, large beaker, polystyrene cup, cotton wool, thermometer and reaction mixture
- the amount of energy released can be measure by a chemical reaction (in solution) by taking the temperature of the reagents, mixing them in a polystyrene cup and the measuring the temperature of the solution at the end.
- reaction profile
- reaction profiles are diagrams that show the relative energies of the reactants and products in a reaction, and how the energy changes over the course of the reaction.
- the initial rise in energy represents the energy needed to start the reaction. this is the activation energy.
- the activation energy is the minimum amount og energy the reactants need to collide with each other and react
- the greater the activation energy, the more energy needed to start the reaction. this has to be supplied e.g. by heating the reaction mixture.
- the activation energy is the minimum amount og energy the reactants need to collide with each other and react
- the initial rise in energy represents the energy needed to start the reaction. this is the activation energy.
- reaction profiles are diagrams that show the relative energies of the reactants and products in a reaction, and how the energy changes over the course of the reaction.
- Exothermic
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