Endotermilised

Endotermilised, or endothermic, describes processes or reactions that absorb energy from their surroundings. In thermodynamic terms, the enthalpy change is positive (ΔH > 0). Because energy enters the system, the temperature of the surroundings tends to fall if there is no external heat source.

Endothermic processes can involve heat, light, or electrical energy being taken up. They contrast with exothermic processes, which release energy to the surroundings. In chemical reactions, endothermic changes often occur when bonds are broken and more energy is required to reach the products than is released during bond formation. In physical changes, melting, sublimation and vaporization are common endothermic steps.

Common examples include the dissolution of ammonium nitrate in water, which absorbs heat; photosynthesis in plants, where light energy is stored as chemical energy; and the thermal decomposition of calcium carbonate when heated. Phase transitions such as ice melting at 0 °C and solid carbon dioxide subliming at room temperature are familiar endothermic processes.

Measuring endothermy typically involves calorimetry to determine heat flows and the enthalpy change of the process. Understanding endothermic processes is important in applications such as cooling packs, where heat absorption provides a cooling effect, and in natural phenomena where energy input drives phase changes or chemical transformations.

Overall, endotermilised events require an external energy source to proceed and result in a net energy gain for the system, with corresponding cooling of the surroundings if heat is not supplied.