Making Real-World Connections with Exothermic Reactions
By Mike Isley
Generations of soldiers ate cold pre-cooked, pre-packaged meals in situations where a fire to heat the “K-rations” was too dangerous or simply not possible. Thanks to a modern thermochemical innovation, military personnel now warm their MREs (meals ready to eat) without a heater or flame. That heating process provides you a great real-world demonstration of thermochemistry, heat of reaction, and exothermic reactions.
Carolina’s Inquiries in Science® Chemistry Series kit, Examining Thermochemistry—with an MRE—helps you show how these sometimes-intangible concepts relate to everyday life. This can engage students in learning and reinforce the lessons and topics.
Heat with no stove or flame
How can you serve a hot meal, especially in a remote area, with no traditional source of heat? Innotech Products, Ltd., solved that problem during Desert Storm (1990–91) by developing a flameless ration heater (FRH) to heat its HeaterMeals® issued to US soldiers. The FRH is a water-absorbent pad filled with food-grade powdered magnesium and iron, glued to the inside of a plastic sleeve. The diner slips a pre-cooked entrée into the sleeve atop the FRH and pours 2 fluid ounces of salt water, provided with the meal, into the sleeve. The FRH pad absorbs the water, causing a highly exothermic corrosion reaction with the formation of magnesium hydroxide, hydrogen gas, and heat (expressed below).
Mg(s) + 2H2O(l) → Mg(OH)2(aq) + H2(g) + heat
The iron is a catalyst that speeds the reaction. From 13 g of magnesium and iron, enough heat generates to create temperatures over 60° C in just 10 min. The only byproducts are magnesium hydroxide (found in milk of magnesia), which is safe to discard in the trash, and hydrogen gas, which dissipates into the atmosphere.
Not just for the military
In addition to military HeaterMeal® rations, Innotech now makes HeaterMeals® available in civilian versions for campers, truck drivers, disaster relief, and mobile meals programs. They also make FRH kits that heat tap water for instant coffee, tea, soups, and hot chocolate.
With the retail-version HeaterMeal® provided in the Examining Thermochemistry Kit, students observe first-hand the effectiveness of the exothermic reaction that heats the lasagna meal in 10 min with no flame or stove. This not only drives home the concept of thermochemsity but also demonstrates the practical uses of chemistry concepts to solve everyday problems.