endothermic

Examples of endothermic in the following topics:

• Exothermic and Endothermic Processes

  • In thermodynamics, these two types of reactions are classified as exothermic or endothermic, respectively.
  • As such, the change in enthalpy for an endothermic reaction is always positive.
  • In order to melt the ice cube, heat is required, so the process is endothermic.
  • In an endothermic reaction, the products are higher in energy than the reactants.
  • Paul Andersen explains how heat can be absorbed in endothermic or released in exothermic reactions.

• Thermochemical Equations

  • The sign of the $\Delta H$ value indicates whether or not the system is endothermic or exothermic.
  • In an endothermic system, the $\Delta H$ value is positive, so the reaction absorbs heat into the system.
  • Notice that in an endothermic reaction like the one depicted above, we can think of heat as being a reactant, just like A and B.

• Energy Changes in Chemical Reactions

  • Endothermic reactions, on the other hand, absorb heat and/or light from their surroundings.
  • For example, decomposition reactions are usually endothermic.
  • In endothermic reactions, the products have more enthalpy than the reactants.
  • Thus, an endothermic reaction is said to have a positive enthalpy of reaction.
  • Significant heat energy is needed for this reaction to proceed, so the reaction is endothermic.

• Heat of Solution

  • The breaking of bonds within the solute, such as the electrostatic attraction between two ions (endothermic)
  • The breaking of intermolecular attractive forces within the solvent, such as hydrogen bonds (endothermic)
  • If more energy is used in breaking bonds than is released upon solute-solvent bond formation, then the overall process is endothermic, and ∆Hsol is positive.
  • Dissolution of sodium chloride (table salt) in water is endothermic.
  • Dissolution of sodium chloride in water is endothermic.

• Animal Bioenergetics

  • If an animal can conserve that heat and maintain a relatively-constant body temperature, it is classified as a warm-blooded animal: an endotherm.
  • Even with insulation, endothermal animals require extensive amounts of energy to maintain a constant body temperature.
  • Smaller endothermic animals have a greater surface area for their mass than larger ones .
  • This results in a smaller endothermic animal having a higher BMR, per body weight, than a larger endothermic animal.
  • The diet of an endothermic animal is determined by its BMR.

• Homeostasis: Thermoregulation

  • Endotherms create most of their heat via metabolic processes, and are colloquially referred to as "warm-blooded."
  • Heat is usually generated from the animal's normal metabolism, but under conditions of excessive cold or low activity, an endotherm generate additional heat by shivering.
  • Many endotherms have a larger number of mitochondria per cell than ectotherms.
  • However, endothermic animals must sustain their higher metabolism by eating more food more often.
  • Sustained energy output of an endothermic animal (mammal) and an ectothermic animal (reptile) as a function of core temperature.

• Heat Conservation and Dissipation

  • In certain climates, endothermic animals have some form of insulation, such as fur, fat, feathers, or some combination thereof.
  • Endotherms use their circulatory systems to help maintain body temperature.
  • In contrast, similar adaptations (as in dolphin flukes and elephant ears) can help cool endotherms when needed.
  • In endotherms, the circulatory system is used to help maintain body temperature, either by vasodilation or vasoconstriction.

• Changes in Temperature

  • Reactions with positive enthalpies—those that absorb heat from their surroundings—are known as endothermic.
  • Endothermic reactions, on the other hand, will be shifted towards product formation as heat is removed from the reaction's surrounding environment.

• Evolution of Reptiles

  • It is not known whether dinosaurs were endotherms or ectotherms.
  • However, given that modern birds are endothermic, the dinosaurs that served as ancestors to birds were probably endothermic as well.

• Le Chatelier's Principle

  • Recall that for an endothermic reaction, heat is absorbed in the reaction, and the value of $\Delta H$ is positive.
  • Thus, for an endothermic reaction, we can picture heat as being a reactant:
  • Conversely, lowering the temperature on an endothermic reaction will shift the equilibrium to the left, since lowering the temperature in this case is equivalent to removing a reactant.
  • Our heat of reaction is positive, so this reaction is endothermic.
  • Since this reaction is endothermic, heat is a reactant.