Exothermic and endothermic
Using exothermic reactions
An exothermic reaction is a chemical or physical process that releases energy, most commonly as heat, into its surroundings.
Enthalpy change (\(\Delta H\)) is the heat absorbed or released by a system during a process at constant pressure.
A neutralization reaction is a chemical reaction between an acid and a base that produces a salt and water.
Mixing epoxy resin and hardener is a chemical reaction called polymerization, where a liquid two-part epoxy system cures into a solid, rigid material through a process called cross-linking
A strong acid completely ionizes in water to produce a large amount of hydrogen ions (\(H^{+}\)), while a weak base only partially ionizes in water, creating fewer hydroxide ions (\(OH^{-}\)).
Stoichiometric refers to the quantitative relationships between reactants and products in a chemical reaction.
Self-heating cans are expensive because they use specialized materials and complex, dual-chambered designs. The chemistry involves containing a reactive mixture, like calcium oxide (\(CaO\)) and water, which is kept separate until the user activates the exothermic reaction to generate heat.
Self-heating cans can only be used once because the process relies on an irreversible chemical reaction that consumes its reactants.
Boiling water releases significantly more heat energy than melting ice because boiling involves breaking the stronger intermolecular bonds of the liquid phase to become a gas, while melting only involves overcoming the forces in the solid phase to become a liquid. Specifically, the energy required for vaporization (boiling) is about seven times greater than the energy needed for fusion (melting) for water.
Boiling water takes significantly more heat energy than melting ice.
Using Endothermic reactions and processes
An endothermic reaction or process is any process that absorbs energy from its surroundings, usually in the form of heat. This energy absorption occurs because the chemical bonds in the reactants require more energy to break than is released when the new bonds in the products are formed.
An advantage of using an ice pack is that it provides pain relief and reduces inflammation and swelling. A disadvantage is that improper use, like applying it for too long or directly to the skin, can cause skin damage such as frostbite or a delayed healing process.