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Lesson 1 - Enthalpy Changes in Chemistry. Starter. When a chemical reaction takes place heat may be given out or taken in. Can you remember the word we use when heat is given out? Can you remember the word we use when heat is taken in?. Energy level diagrams. - PowerPoint PPT Presentation
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Lesson 1 - Enthalpy Changes in Chemistry
Lesson 1 - Enthalpy Changes in Chemistry
StarterStarter
• When a chemical reaction takes place heat may be given out or taken in.
1.Can you remember the word we use when heat is given out?
2.Can you remember the word we use when heat is taken in?
Energy level diagramsEnergy level diagrams
Heat taken inHeat taken in Heat given outHeat given out
Change in energyChange in energy
ObjectivesObjectives
MustRecall and use the terms ENDOTHERMIC and EXOTHERMICShouldDescribe examples of ENDOTHERMIC and EXOTHERMIC reactions.CouldExplain ENDOTHERMIC and EXOTHERMIC reactions using energy level diagrams.
Reactants Description of reaction Initial temp. / °C
Final temp. /°C
Change in temp. ΔT / °C
Exo or endo?
Sodium and chlorine gas
https://www.youtube.com/watch?v=Mx5JJWI2aaw
N/A (demo)
N/A (demo)
N/A (demo)
Sugar and sulfuric acid
https://www.youtube.com/watch?v=nqDHwd9rG0s
N/A (demo)
N/A (demo)
N/A (demo)
Dissolving ammonium nitrate
https://www.youtube.com/watch?v=G3S4YvhhAic
N/A (demo)
N/A (demo)
N/A (demo)
Barium hydroxide and ammonium nitrate
https://www.youtube.com/watch?v=GQkJI-Nq3Os
N/A (demo)
N/A (demo)
N/A (demo)
DefinitionsDefinitions
Exothermic ReactionsExothermic Reactions
DefinitionsDefinitions
Endothermic ReactionsEndothermic Reactions
Which of the following statements is correct?
Which of the following statements is correct?
1. The products of a chemical reaction have more energy than the reactants so an exothermic reaction must have taken place.
2. The products of a chemical reaction have less energy than the reactants so an endothermic reaction must have taken place.
3. The products of a chemical reaction have less energy than the reactants so an exothermic reaction must have taken place.
1. The products of a chemical reaction have more energy than the reactants so an exothermic reaction must have taken place.
2. The products of a chemical reaction have less energy than the reactants so an endothermic reaction must have taken place.
3. The products of a chemical reaction have less energy than the reactants so an exothermic reaction must have taken place.
Which of the following statements is correct?
Which of the following statements is correct?
The products of a chemical reaction have less energy than the reactants so an exothermic reaction must have taken place.
Q - How can we illustrate this?
Energy level diagrams – copy into your notes
Energy level diagrams – copy into your notes
Endothermic Exothermic
Heat taken inHeat taken in Heat given outHeat given out
Energy level of products is higher than reactants so heat taken in.Energy level of products is higher than reactants so heat taken in.
Energy level of products is lower than reactants so heat given out.Energy level of products is lower than reactants so heat given out.
QuestionQuestion
AnswerAnswer
Wrap up – Can you recall?Wrap up – Can you recall?
• Draw an energy profile for an exothermic reaction marking clearly the activation energy.