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 ID: 277912
Download Presentation The PPT/PDF document "Module 3" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Module 3
Lesson 1 - Enthalpy Changes in ChemistrySlide2
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?Slide3
AfL - Energy level diagrams
Which diagram do you think is
endothermic
and which is
exothermic
?
Heat taken in
Heat given outSlide4
Change in energy
Chemical reactants have a certain amount of
chemical energy
stored within them.
When the reaction has taken place they have either
more or less energy stored within them than before.Slide5
Objectives
Must
Recall and use the terms ENDOTHERMIC and EXOTHERMIC
Should
Describe examples of ENDOTHERMIC and EXOTHERMIC reactions.
CouldExplain ENDOTHERMIC and EXOTHERMIC reactions using energy level diagrams.Slide6
Reactants
Description
of reaction
Initial temp. / °C
Final temp.
/°CChange in temp. ΔT / °CExo or endo?
Sodium and chlorine gas
N/A (demo)
N/A (demo)N/A (demo)Sugar
and sulphuric acidN/A (demo)
N/A (demo)N/A (demo)Dissolving ammonium nitrate
N/A (demo)
N/A (demo)
N/A (demo)
Barium hydroxide and ammonium nitrate
N/A (demo)
N/A (demo)
N/A (demo)Slide7
Exothermic Demos
Chlorine gas reacting with sodium metal (video)
Concentrated
sulphuric
acid and sugar (demo)Slide8
Definitions
In your notes write down a
definition of an exothermic reaction
;
AND
Describe what happened in the two experiments you have just seen.
Be prepared to share your answers –
I could ask you!Slide9
Exothermic Reactions
Correct definition:
An
exothermic
chemical reaction where the products have less energy than the reactants.
Energy is given out to the surroundings (temperature goes up)
.Slide10
Endothermic Demos
Dissolving ammonium nitrate
Reaction between ammonium nitrate and barium hydroxide.Slide11
Definitions
In your notes write down a
definition of an endothermic reaction
;
AND
Describe what happened in the two experiments you have just seen.
Be prepared to share your answers –
I could ask you!Slide12
Endothermic Reactions
Correct definition:
An
endothermic
chemical reaction is where the products have more energy than the reactants.
Energy is taken in from the surroundings (temperature goes down)
.Slide13
AfL
- Which of the following statements is correct?
The products of a chemical reaction have more energy than the reactants so an exothermic reaction must have taken place.
The products of a chemical reaction have less energy than the reactants so an endothermic reaction must have taken place.
The products of a chemical reaction have less energy than the reactants so an exothermic reaction must have taken place.Slide14
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?Slide15
Energy level diagrams – copy into your notes
Endothermic Exothermic
Heat taken in
Heat given out
Energy level of products is higher than reactants so heat taken in.
Energy level of products is lower than reactants so heat given out.Slide16
QuestionSlide17
AnswerSlide18
Plenary – Can you recall?
Draw an energy profile for an exothermic reaction marking clearly the activation energy.Slide19
Homework
Question booklet.