Changes

: [[Freezing]], [[Condensing]] and [[Depositing]] are [[exothermic]] changes because it releases they release [[energy]] when it happensthey happen. The [[material]] has less [[energy]] after it has they have happened. However, there is usually no increase in [[temperature]] because the [[material]] is being usually cooled to [[State Change|change state]] because the surroundings are colder than the [[material]] during this process. ==Key Stage 4=====Meaning===An [[exothermic]] process is one that gives out [[energy]]. This usually causes surroundings to increase in [[temperature]]. ===About Exothermic Processes=======Foundation====: [[Exothermic]] [[Chemical Reaction|reactions]] usually require [[energy]] to begin. This is called the [[Activation Energy|activation energy]].: In an [[exothermic]] process the [[Potential Energy|potential energy]] stored in the [[product]]s is less than the [[Potential Energy|potential energy]] stored in the [[reactant]]s. {| class="wikitable"|-|[[File:ExothermicSketchGraphKS4.png|center|500px]]|-| style="height:20px; width:500px; text-align:center;" |To start the [[Chemical Reaction|reaction]] an [[Activation Energy|activation energy]] is needed. This is usually achieved by initially [[heating]] the [[reactant]]s. Once the [[Chemical Reaction|reaction]] starts the [[energy]] stored in the [[reactant]]s is released in the [[Chemical Reaction|chemical reaction]] making the [[material]] increase in [[temperature]]. The [[product]]s now have less [[energy]] than the [[reactant]]s.|} ====Higher====: In a [[Chemical Reaction|chemical reaction]] [[energy]] is needed to break the [[Chemical Bond|chemical bonds]] holding the [[atom]]s together.: In an [[exothermic]] [[Chemical Reaction|reaction]] [[energy]] is then released as [[atom]]s form new [[Chemical Bond|chemical bonds]].: In an [[exothermic]] [[Chemical Reaction|reaction]] more [[energy]] is released in the formation of new [[Chemical Bond|bonds]] in the [[product]] than is taken in in the breaking of [[Chemical Bond|bonds]] in the [[reactant]]s. So there is a net output of [[energy]]. ===Examples=======Higher===='''Example 1'''{| class="wikitable"|-|[[File:StructuralDiagramMethane+Oxygen.png|center|500px]]|-| style="height:20px; width:200px; text-align:center;" |In the [[Chemical Reaction|reaction]] between [[Methane]] and [[Oxygen]] the [[Chemical Bond|chemical bonds]] in the [[reactant]]s must be broken first before the [[Chemical Bond|bonds]] in the [[product]]s are formed.|} {| class="wikitable"|-| style="height:20px; width:100px; text-align:center;" |'''Bond'''| style="height:20px; width:150px; text-align:center;" |'''Energy in kJ/mol'''|-| style="height:20px; width:100px; text-align:center;" |C-H| style="height:20px; width:150px; text-align:center;" |413|-| style="height:20px; width:100px; text-align:center;" |O=O| style="height:20px; width:150px; text-align:center;" |498|-| style="height:20px; width:100px; text-align:center;" |O-H| style="height:20px; width:150px; text-align:center;" |464|-| style="height:20px; width:100px; text-align:center;" |C=O| style="height:20px; width:150px; text-align:center;" |799|} There are 4 C-H [[Chemical Bond|bonds]] and 2 O=O [[Chemical Bond|bonds]]. 4 x 413 + 2 x 498 = 2648kJ Therefore 2648kJ/mol are needed to break the [[Chemical Bond|bonds]] in the [[reactant]]s. There are 2 C=O [[Chemical Bond|bonds]] and 4 O-H [[Chemical Bond|bonds]]. 2 x 799 + 4 x 464 = 3454kJ Therefore 3454kJ/mol is released when the [[Chemical Bond|bonds]] in the [[product]]s form. Once the [[Chemical Reaction|reaction]] is complete 806kJ will be released. '''Example 2'''{| class="wikitable"|-|[[File:StructuralDiagramHydrogen+Nitrogen.png|center|500px]]|-| style="height:20px; width:200px; text-align:center;" |In the [[Chemical Reaction|reaction]] between [[Hydrogen]] and [[Nitrogen]] the [[Chemical Bond|chemical bonds]] in the [[reactant]]s must be broken first before the [[Chemical Bond|bonds]] in the [[product]]s are formed.|} {| class="wikitable"|-| style="height:20px; width:100px; text-align:center;" |'''Bond'''| style="height:20px; width:150px; text-align:center;" |'''Energy in kJ/mol'''|-| style="height:20px; width:100px; text-align:center;" |H-H| style="height:20px; width:150px; text-align:center;" |436|-| style="height:20px; width:100px; text-align:center;" |N≡N| style="height:20px; width:150px; text-align:center;" |941|-| style="height:20px; width:100px; text-align:center;" |N-H| style="height:20px; width:150px; text-align:center;" |391|} There are 3 H-H [[Chemical Bond|bonds]] and 1 N≡N [[Chemical Bond|bonds]]. 3 x 436 + 1 x 941 = 2249kJ Therefore 2249kJ/mol are needed to break the [[Chemical Bond|bonds]] in the [[reactant]]s. There are 6 N-H [[Chemical Bond|bonds]]. 6 x 391 = 2346kJ Therefore 2346kJ/mol is released when the [[Chemical Bond|bonds]] in the [[product]]s form. Once the [[Chemical Reaction|reaction]] is complete 97kJ will be released. ===References=======AQA==== :[https://www.amazon.co.uk/gp/product/0008158762/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0008158762&linkCode=as2&tag=nrjc-21&linkId=a0fffa35b3ea49a63404f6704e0df7cc ''Exothermic reaction, pages 173-5, 178-81, 211,216-7, GCSE Chemistry; Student Book, Collins, AQA '']:[https://www.amazon.co.uk/gp/product/0198359373/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359373&linkCode=as2&tag=nrjc-21&linkId=952a73bbb09d222ecc4b50d200679849 ''Exothermic reactions, page 134, GCSE Biology; Third Edition, Oxford University Press, AQA '']:[https://www.amazon.co.uk/gp/product/1782946381/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946381&linkCode=as2&tag=nrjc-21&linkId=5ec5fc3f6429e30c1d9ab9bca2bccf93 ''Exothermic reactions, page 165, GCSE Combined Science Trilogy; Biology, CGP, AQA '']:[https://www.amazon.co.uk/gp/product/1782945954/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945954&linkCode=as2&tag=nrjc-21&linkId=100574c08fbbb64318256eb79ed61a76 ''Exothermic reactions, page 179, GCSE Biology, CGP, AQA '']:[https://www.amazon.co.uk/gp/product/1782945563/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945563&linkCode=as2&tag=nrjc-21&linkId=9a1d023a374038e6072f33c4f3cf808b ''Exothermic reactions, page 61, GCSE Biology; The Revision Guide, CGP, AQA '']:[https://www.amazon.co.uk/gp/product/1471851354/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851354&linkCode=as2&tag=nrjc-21&linkId=9012a0d354024419214fb3ad5ac44ba0 ''Exothermic reactions, pages 106, 231-2, GCSE Combined Science Trilogy 1, Hodder, AQA '']:[https://www.amazon.co.uk/gp/product/0198359381/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359381&linkCode=as2&tag=nrjc-21&linkId=47c8d1ae58d8b3a5e2094cd447154558 ''Exothermic reactions, pages 112-113, 114-119, GCSE Chemistry; Third Edition, Oxford University Press, AQA '']:[https://www.amazon.co.uk/gp/product/1471851346/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851346&linkCode=as2&tag=nrjc-21&linkId=3ac654f4b0da781c49c855a1af4c92ea ''Exothermic reactions, pages 129-30, GCSE Chemistry, Hodder, AQA '']:[https://www.amazon.co.uk/gp/product/178294639X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=178294639X&linkCode=as2&tag=nrjc-21&linkId=51599bb45a2bfaf7c1b6a978b2ca2616 ''Exothermic reactions, pages 152, 154, 155, 157, 159, 182-184, GCSE Combined Science Trilogy; Chemistry, CGP, AQA '']:[https://www.amazon.co.uk/gp/product/1782945962/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945962&linkCode=as2&tag=nrjc-21&linkId=476bb5c8d1dfb5c08ac81b6d4d1c98d8 ''Exothermic reactions, pages 177, 179, 180, 182, 184, 214-216, GCSE Chemistry, CGP, AQA '']:[https://www.amazon.co.uk/gp/product/1782945571/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945571&linkCode=as2&tag=nrjc-21&linkId=9e29fad914244909903e5e93f8a01d121 ''Exothermic reactions, pages 61-63, 72, 73, GCSE Chemistry; The Revision Guide, CGP, AQA '']:[https://www.amazon.co.uk/gp/product/1471851354/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851354&linkCode=as2&tag=nrjc-21&linkId=9012a0d354024419214fb3ad5ac44ba0 ''Exothermic reactions; reaction profiles, pages 233, 235, GCSE Combined Science Trilogy 1, Hodder, AQA '']:[https://www.amazon.co.uk/gp/product/0008158754/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0008158754&linkCode=as2&tag=nrjc-21&linkId=27ad53b0283feeff7fc5ae04a9e205f283 ''Exothermic, page 36-7, GCSE Biology; Student Book, Collins, AQA '']:[https://www.amazon.co.uk/gp/product/1471851346/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851346&linkCode=as2&tag=nrjc-21&linkId=3ac654f4b0da781c49c855a1af4c92ea ''Exothermic; reaction profiles, page 131, GCSE Chemistry, Hodder, AQA ''] ====Edexcel==== :[https://www.amazon.co.uk/gp/product/1292120207/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120207&linkCode=as2&tag=nrjc-21&linkId=22455ff53961978667722edaa64c0be5 ''Exothermic reactions, page 170, GCSE Biology, Pearson, Edexcel '']:[https://www.amazon.co.uk/gp/product/1782948120/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782948120&linkCode=as2&tag=nrjc-21&linkId=dedef775c6a43dbb0a609441525adac0 ''Exothermic reactions, page 270, GCSE Biology, CGP, Edexcel '']:[https://www.amazon.co.uk/gp/product/1292120193/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120193&linkCode=as2&tag=nrjc-21&linkId=572df39392fb4200db8391d98ae6314e ''Exothermic reactions, pages 118, 252, 258-259, GCSE Combined Science, Pearson Edexcel '']:[https://www.amazon.co.uk/gp/product/1782945741/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945741&linkCode=as2&tag=nrjc-21&linkId=30da4f2178da182547b62a7329d13b57 ''Exothermic reactions, pages 134, 136, GCSE Combined Science; The Revision Guide, CGP, Edexcel '']:[https://www.amazon.co.uk/gp/product/1292120215/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120215&linkCode=as2&tag=nrjc-21&linkId=8f96ddb76196848bafdb124354e4cf77 ''Exothermic reactions, pages 138, 144-145, GCSE Chemistry, Pearson, Edexcel '']:[https://www.amazon.co.uk/gp/product/1782948147/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782948147&linkCode=as2&tag=nrjc-21&linkId=f63dcd8345f4e49c717b39a228a36c7c ''Exothermic reactions, pages 243, 244, 248-250, GCSE Chemistry, CGP, Edexcel '']:[https://www.amazon.co.uk/gp/product/1782945725/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945725&linkCode=as2&tag=nrjc-21&linkId=694be7494de75af3349537d34e13f7f0 ''Exothermic reactions, pages 83, 85, GCSE Chemistry; The Revision Guide, CGP, Edexcel '']:[https://www.amazon.co.uk/gp/product/1292120193/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120193&linkCode=as2&tag=nrjc-21&linkId=572df39392fb4200db8391d98ae6314e ''Exothermic reactions; equilibrium, page 239, GCSE Combined Science, Pearson Edexcel '']:[https://www.amazon.co.uk/gp/product/1292120215/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120215&linkCode=as2&tag=nrjc-21&linkId=8f96ddb76196848bafdb124354e4cf77 ''Exothermic reactions; equilibrium, page 95, GCSE Chemistry, Pearson, Edexcel ''] ====OCR====:[https://www.amazon.co.uk/gp/product/1782945660/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945660&linkCode=as2&tag=nrjc-21&linkId=83aa4500ad7759e7f401a1c5ba5df758 ''Exothermic reactions, page 20, Gateway GCSE Biology; The Revision Guide, CGP, OCR '']:[https://www.amazon.co.uk/gp/product/1782945679/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945679&linkCode=as2&tag=nrjc-21&linkId=a2db42f7b4bdf10cafaafa3bb9120940 ''Exothermic reactions, page 41, 42, Gateway GCSE Chemistry; The Revision Guide, CGP, OCR '']:[https://www.amazon.co.uk/gp/product/0198359810/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359810&linkCode=as2&tag=nrjc-21&linkId=d768d99f1a06f7c12fab40e5aef85a55 ''Exothermic reactions, page 41, Gateway GCSE Biology, Oxford, OCR '']:[https://www.amazon.co.uk/gp/product/0198359829/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359829&linkCode=as2&tag=nrjc-21&linkId=90e8d7b4f039d53035238fa0320fe00b ''Exothermic reactions, pages 102-103, 105, 186, Gateway GCSE Chemistry, Oxford, OCR '']:[https://www.amazon.co.uk/gp/product/1782945695/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945695&linkCode=as2&tag=nrjc-21&linkId=ceafcc80bcad6b6754ee97a0c7ceea53 ''Exothermic reactions, pages 18, 111, Gateway GCSE Combined Science; The Revision Guide, CGP, OCR '']