IB Chemistry Topic 5 Energetics and thermochemistry
5.1 Measuring energy changes SL
• Heat is a form of energy.
• Temperature is a measure of the average kinetic energy of the particles.
• Total energy is conserved in chemical reactions.
• Chemical reactions that involve transfer of heat between the system and the surroundings are described as endothermic or exothermic.
• The enthalpy change (∆H) for chemical reactions is indicated in kJ mol1.
• ∆H values are usually expressed under standard conditions, given by ∆H°, including standard states.
• Calculation of the heat change when the temperature of a pure substance is changed using q=mc∆T.
• A calorimetry experiment for an enthalpy of reaction should be covered and the results evaluated.
• Temperature is a measure of the average kinetic energy of the particles.
• Total energy is conserved in chemical reactions.
• Chemical reactions that involve transfer of heat between the system and the surroundings are described as endothermic or exothermic.
• The enthalpy change (∆H) for chemical reactions is indicated in kJ mol1.
• ∆H values are usually expressed under standard conditions, given by ∆H°, including standard states.
• Calculation of the heat change when the temperature of a pure substance is changed using q=mc∆T.
• A calorimetry experiment for an enthalpy of reaction should be covered and the results evaluated.

The difference between temperature and heat, how to draw enthalpy diagrams. How to measure heat change Q and determine the enthalpy of a reaction using calorimetry and Q=mcdT with practice problems
1:03 Enthalpy H 1:47 dH exothermic and endothermic reactions 2:56 Enthalpy diagrams 5:06 Examples of exothermic reactions 5:49 Measuring heat energy change Q 6:22 Calorimetry 8:07 Calculations for calorimetry 9:24 Example problem 1 10:27 Example problem 2 
5.2 Hess's Law SL
• The enthalpy change for a reaction that is carried out in a series of steps is equal to the sum of the enthalpy changes for the individual steps.
• Application of Hess’s Law to calculate enthalpy changes.
• Calculation of ∆𝐻 reactions using ∆Hf° data.
• Determination of the enthalpy change of a reaction that is the sum of multiple reactions with known enthalpy changes.
• Application of Hess’s Law to calculate enthalpy changes.
• Calculation of ∆𝐻 reactions using ∆Hf° data.
• Determination of the enthalpy change of a reaction that is the sum of multiple reactions with known enthalpy changes.

How to use Hess' Law to work out enthalpy problems. The most valuable think to learn is how to work out if the formula is products less reactants or reactants less products. Practice problems for Hess Law, enthalpy of formation and enthalpy of combustion
0:12 Hess's law definition 0:52 Hess's law reaction diagram 1:15 Hess's law example problem 1:46 Enthalpy of formation definition 2:50 Enthalpy of formation example problem 1 4:22 Enthalpy of formation example problem 2 5:43 Enthalpy of combstion definition 6:19 Enthalpy of combustion example problem 7:22 Summary of formula 
5.3 Bond enthalpies SL
• Bondforming releases energy and bondbreaking requires energy.
• Average bond enthalpy is the energy needed to break one mol of a bond in a gaseous molecule averaged over similar compounds.
• Calculation of the enthalpy changes from known bond enthalpy values and comparison of these to experimentally measured values.
• Sketching and evaluation of potential energy profiles in determining whether reactants or products are more stable and if the reaction is exothermic or endothermic.
• Discussion of the bond strength in ozone relative to oxygen in its importance to the atmosphere.
• Average bond enthalpy is the energy needed to break one mol of a bond in a gaseous molecule averaged over similar compounds.
• Calculation of the enthalpy changes from known bond enthalpy values and comparison of these to experimentally measured values.
• Sketching and evaluation of potential energy profiles in determining whether reactants or products are more stable and if the reaction is exothermic or endothermic.
• Discussion of the bond strength in ozone relative to oxygen in its importance to the atmosphere.

How to work out the formula and practice calculations for determining bond enthalpy
0:13 Bond enthalpy definition 0:40 Bond enthalpy formula diagram 1:09 Enthalpy level diagram 1:35 Bond enthalpy reference table 1:56 Example problem bond enthalpy 4:31 Bond enthalpy of ozone 5:26 Enthalpy level diagram of ozone 
EXPERIMENTAL VIDEOS:



EXAM PAST PAPER QUESTION VIDEOS SL:







End of Unit Quiz Topic 5 SL:
When you are confident with all the concepts please try this quiz. These are based of IB Chemistry exam past paper 1 questions. Make sure you get 100%. If you don't please refresh the page and try it again.

15.1 Energy cycles HL
• Representative equations (eg M+(g) à M+(aq)) can be used for enthalpy/energy of hydration, ionization, atomization, electron affinity, lattice, covalent bond and solution.
• Enthalpy of solution, hydration enthalpy and lattice enthalpy are related in an energy cycle.
• Construction of BornHaber cycles for group 1 and 2 oxides and chlorides.
• Construction of energy cycles from hydration, lattice and solution enthalpy. For example dissolution of solid NaOH or NH4Cl in water.
• Calculation of enthalpy changes from BornHaber or dissolution energy cycles.
• Relate size and charge of ions to lattice and hydration enthalpies.
• Perform lab experiments which could include single replacement reactions in aqueous solutions.
• Enthalpy of solution, hydration enthalpy and lattice enthalpy are related in an energy cycle.
• Construction of BornHaber cycles for group 1 and 2 oxides and chlorides.
• Construction of energy cycles from hydration, lattice and solution enthalpy. For example dissolution of solid NaOH or NH4Cl in water.
• Calculation of enthalpy changes from BornHaber or dissolution energy cycles.
• Relate size and charge of ions to lattice and hydration enthalpies.
• Perform lab experiments which could include single replacement reactions in aqueous solutions.

How to determine work with Born Haber cycles and determine enthalpy of solution and enthalpy of hydration
0:20 Enthalpy of formation 2:26 Enthalpy of atomisation 3:02 Ionisation energy 3:46 Electron affinity 4:26 Lattice enthalpy (dissociation) 6:51 BornHaber cycle 7:58 Example problem 10:14 Solvation 10:57 Enthalpy of solution 11:36 Entlhalpy of hydration 12:00 Example problem enthalpy of solution 
15.2 Entropy and spontaneity HL
• Entropy (S) refers to the distribution of available energy among the particles. The more ways the energy can be distributed the higher the entropy.
• Gibbs free energy (G) relates the energy that can be obtained from a chemical reaction to the change in enthalpy (ΔH), change in entropy (ΔS), and absolute temperature (T).
• Entropy of gas>liquid>solid under same conditions.
• Prediction of whether a change will result in an increase or decrease in entropy by considering the states of the reactants and products.
• Calculation of entropy changes (ΔS) from given standard entropy values (Sº).
• Application of ΔG° = ΔH°  TΔS° in predicting spontaneity and calculation of various conditions of enthalpy and temperature that will affect this.
• Relation of ΔG to position of equilibrium.
• Gibbs free energy (G) relates the energy that can be obtained from a chemical reaction to the change in enthalpy (ΔH), change in entropy (ΔS), and absolute temperature (T).
• Entropy of gas>liquid>solid under same conditions.
• Prediction of whether a change will result in an increase or decrease in entropy by considering the states of the reactants and products.
• Calculation of entropy changes (ΔS) from given standard entropy values (Sº).
• Application of ΔG° = ΔH°  TΔS° in predicting spontaneity and calculation of various conditions of enthalpy and temperature that will affect this.
• Relation of ΔG to position of equilibrium.

How to do entropy and Gibbs free energy calculations for HL
0:11 Entropy 1:50 Entropy formula 3:01 Example problem entropy 3:37 Gibbs free energy 4:31 Summary of formula 5:15 Summary of trends and spontaneity 7:40 Example problem 1 Gibbs 8:16 Example problem 2 Gibbs 
EXAM PAST PAPER QUESTION VIDEOS HL:



End of Unit Quiz Topic 5 HL:
When you are confident with all the concepts please try this quiz. These are based of IB Chemistry exam past paper 1 questions. Make sure you get 100%. If you don't please refresh the page and try it again.
