Everyday application of Hess's Law

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Everyday application of Hess's Law


Burning calories, consuming food, driving home, we all should be familiar with these actions because we do them everyday, but what some of us don't realise is that all these actions related one fundamental law of conservation of energy, Hess's Law.  Hess's Law states that: regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of all changes. [1]  We will further discover how our indrustries, human body and drug production are related to this law and to better understand the science behind it.

Industries

Today, all our mass and low cost production depends on factories and industries and all these industries require huge amount of energy.  To keep everything the most efficient possible, these industries has to determine the method that is the most effective to produce a product based on the energy needed or released.  
For example:  Car companies must determine how much energy the car engine uses when it burns fuel, this can help them determine if their car is efficient or not and if it is worth taking the risk to build a fuel consuming car. 
Industries can measure how much energy each process releases so they can know whish is the most effective energy choices.
 

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Human body

When we talk about the burning of energy, we can also think about the human body.  When we work out, we think about the human body burning calories.  Hess’ Law shows that the energy change is independent of the pathway, this means that the same amount of energy is released through the burning food.  A lot of weight lose applications uses this concept to calculate the amount of calories burned during a work out and a lot of the time, they are pretty accurate thanks to the Hess's Law.  So food compagnies also use this concept to calculate the amount of energy released by a body while breaking down the bonds in the glucose in foods to find the amount of calories in the food [2].


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Pharmaceutical industry

For people that lives in cold places, buying the best hand warmer is crucial for survival, these little pack that warms our freezing hands are the best thing to have in winter or when feeling cold.  Hand warmers are composed of iron, water, activated carbon, vermiculite (water reservoir) and salt [3].  They work by producing heat from the exothermic oxidation of iron when exposed to air, this means that they release heat to the surrounding environment which most of the time is your hands.  The Hess's Law is especially helpful because the manufactures can use this concept to find out the total change in enthalpy and deduce how many amount of each ingredient is needed to keep your warm for hours! 
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Another example of the use of Hess's Law in drugs is cold pack or instant ice pack.  In the cold pack one side of it containes water while the other one containes ammonium nitrate, calcium ammonium nitrate or urea [4]. When the inner bag of water is broken by squeezing the package, it allowes to dissolve the solid in an endothermic reaction, where heat is being absorbed from the surrounding to inside the pack.  Here again, the Hess's Law is used to calculate the change in enthalpy this time possitive and also to find the right amount of ingredient needed to keep you cool.

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Sources:
 
  1. "Hess's Law" - Chemistry LibreTexts, 2016 Sep 20, 2019 Feb 27, https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Thermodynamics/Thermodynamic_Cycles/Hess's_Law  [1]
  2.  “Applications - Enthalpy of Reaction and Hess's Law.” Google Sites, 2019 Feb 27, sites.google.com/site/experiment6enthalpy/applications.  [2]
  3.  “How Do Re-Usable Hand Warmers Work?” Science Focus - BBC Focus Magazine, www.sciencefocus.com/science/how-do-re-usable-hand-warmers-work/.  [3]
  4. “Hot and Cold Packs: A Thermochemistry Activity.” Carolina Biological Supply: World-Class Support for Science & Math, www.carolina.com/teacher-resources/Interactive/hot-and-cold-packs-a-thermochemistry-activity/tr29415.tr.  [4]  

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