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    5.1 Measuring energy changes 

    Understandings

    1. Heat is a form of energy.
    2. Temperature is a measure of the average kinetic energy of the particles.
    3. Total energy is conserved in chemical reactions.
    4. Chemical reactions that involve transfer of heat between the system and the surroundings are described as endothermic or exothermic.
    5. The enthalpy change (H) for chemical reactions is indicated in kJ mol−1.
    6. change in H values are usually expressed under standard conditions, known as H , including standard states. Guidance: Enthalpy changes of combustion (H c ) and formation (Hf ) should be covered.

    Applications and skills

    1. Calculation of the heat change when the temperature of a pure substance is changed using q =mc T. Guidance: The specific heat capacity of water is provided in the IB Data booklet in section 2.
    2. A calorimetry experiment for an enthalpy of reaction should be covered and the results evaluated. Guidance: Consider reactions in aqueous solution and combustion reactions.
    3. Standard state refers to the normal, most pure stable state of a substance measured at 100 kPa.
    4. Temperature is not a part of the definition of standard state, but 298 K is commonly given as the temperature of interest.
    5. Students can assume the density and specific heat capacities of aqueous solutions are equal to those of water, but should be aware of this limitation.
    6. Heat losses to the environment and the heat capacity of the calorimeter in experiments should be considered, but the use of a bomb calorimeter is not required.

    Inquiry questions

    5.1 How can you measure and calculate heat changes in a reaction?​
    ​5.1 To what extent is the knowledge and understanding of enthalpy necessary in cooking?

    Unit content overview

    Endothermic and Exothermic 

    Endothermic Practical 

    This is a very visual demo for a endothermic reaction 

    Enthalpy 

    Enthalpy changes of combustion 

    1. Watch the video 
    2. Read Pearson textbook pages 218-220
    3. Complete the worked example on page 219
    4. Explain the calculation in your own words using the Flipgrid 

    Class practical: Enthalpy of combustion of alcohol 

    Task:
    1. Complete the practical 
    2. Record your results in the spreadsheet below 
    3. Analyse your results 

    Practice questions - Enthalpy changes of combustion 

    Complete exercises 7-11 on page 220-221 in the pearsons Textbook
    Syllabus points covered:
    U.5: The enthalpy change (H) for chemical reactions is indicated in kJ mol−1.

    U.6: change in H values are usually expressed under standard conditions, known as H , including standard states. Guidance: Enthalpy changes of combustion (H c ) and formation (Hf ) should be covered.

    ​
    ​AS.1: Calculation of the heat change when the temperature of a pure substance is changed using q =mc T. Guidance: The specific heat capacity of water is provided in the IB Data booklet in section 2.

    AS.2: A calorimetry experiment for an enthalpy of reaction should be covered and the results evaluated. Guidance: Consider reactions in aqueous solution and combustion reactions.

    Enthalpy changes of solutions 

    Please note that the video is covering also much of the Hess's law which is our next topic

    ​

    Prescribed class practical: Copper Sulfate and Zinc 

    Task:
    1. Complete the practical using the instructions
    2. Record your results in the spreadsheet 
    3. Process your results (capitalize on the crowdsourcing and use other groups results as trials)
    4. Analyse your results and complete a evaluation 

    Enthalpy change - Cooking Lab 

    The video to this task are taken from a EdX course provided by HarvardX please see the link and web address to it below:
    https://courses.edx.org/courses/course-v1:HarvardX+SPU27.1x+3T2019/course/
    Task:
    1. Watch the following video:
    - Enthalpy equation - use in cooking 
    - Cooking a perfect egg using chemistry 
    2. Take the quiz below 

    ​3. Conduct the following experiment:

    Taking into consideration that not all heat from the boiling water is going into the egg, find out what mass of boiling water you actually need in real life to cook an egg to the same consistency than an egg that would have been cooked at exactly 64 degree celsius.  
     - come up with your own method 
     - take pictures of your experiment set up and the eggs after your trails 
     - video your experiment and add them into the following Google folder along with your method in a Google doc (Make sure you are naming your files using your own name or an appropriate Nickname - please also note that this folder is public so will be your video and method)
     - 
    How to cook a perfect egg - Introduction video 
    Enthalpy equation - use in cooking  
    Cooking a perfect egg using chemistry ​

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