instant cold packs are often used for injuries. Describe the relationship between the sign for ethalpy, entropy and Gibbs free energy of the reaction taking place inside an instant cold pack. Write claim, evidence, and reasoning

Question

instant cold packs are often used for injuries. Describe the relationship between the sign for ethalpy, entropy and Gibbs free energy  of the reaction taking place inside an instant cold pack. Write claim, evidence, and reasoning

GPT-4o mini · Answer

**Claim:** The reaction occurring in an instant cold pack is endothermic, characterized by a positive change in enthalpy ($ \Delta H > 0 $), an increase in entropy ($ \Delta S > 0 $), and a negative change in Gibbs free energy ($ \Delta G < 0 $) under the appropriate conditions, indicating that the reaction is spontaneous. **Evidence:** 1. **Enthalpy ($ \Delta H $)**: The reaction in an instant cold pack involves the dissolution of ammonium nitrate ($ NH_4NO_3 $) or similar salts in water. This process absorbs heat from the surroundings, resulting in a drop in temperature, which indicates a positive change in enthalpy ($ \Delta H > 0 $). 2. **Entropy ($ \Delta S $)**: When ammonium nitrate dissolves in water, it dissociates into ions, increasing disorder in the system. The dissolution process leads to an increase in the number of microstates available to the system, thus resulting in a positive change in entropy ($ \Delta S > 0 $). 3. **Gibbs Free Energy ($ \Delta G $)**: The relationship between enthalpy, entropy, and Gibbs free energy is described by the Gibbs free energy equation: $$ \Delta G = \Delta H - T \Delta S $$ For the dissolution of ammonium nitrate, although $ \Delta H $ is positive, $ T \Delta S $ is also positive and can be greater than $ \Delta H $ at higher temperatures, leading to $ \Delta G < 0 $ for the spontaneous nature of the process at room temperature. **Reasoning:** The endothermic reaction indicates that the process requires energy input from the surroundings, which is manifested as a temperature drop in the cold pack. The increase in entropy due to the dissociation of solid ammonium nitrate into ions supports the concept that the resulting solution is more disordered than the initial solid state. According to the Gibbs free energy equation, if the increase in entropy is sufficiently large relative to the positive change in enthalpy, the overall change in Gibbs free energy will be negative ($ \Delta G < 0 $), allowing the reaction to occur spontaneously. This spontaneous dissolution results in the effective cooling observed with instant cold packs, underscoring the relationships between enthalpy, entropy, and Gibbs free energy in this context.