heat capacity

Examples of heat capacity in the following topics:

• Water’s High Heat Capacity

  • The high heat capacity of water has many uses.
  • The water then remains hot for a long time due to its high heat capacity.
  • Water's high heat capacity is a property caused by hydrogen bonding among water molecules.
  • Water has the highest specific heat capacity of any liquid.
  • In fact, the specific heat capacity of water is about five times more than that of sand.

• Heat Conservation and Dissipation

  • Animals conserve or dissipate heat in a variety of ways.
  • For example, vasodilation brings more blood and heat to the body surface, facilitating radiation and evaporative heat loss, which helps to cool the body.
  • Many animals, especially mammals, use metabolic waste heat as a heat source.
  • In cases of severe cold, a shivering reflex is activated that generates heat for the body.
  • The same animals may climb onto rocks to capture heat during a cold desert night.

• Lung Volumes and Capacities

  • Different animals exhibit different lung capacities based on their activities.
  • At maximal capacity, an average lung can hold almost six liters of air; however, lungs do not usually operate at maximal capacity.
  • Air in the lungs is measured in terms of lung volumes and lung capacities .
  • The lung capacities are measurements of two or more volumes.
  • The total lung capacity of the adult male is six liters.

• Water’s Heat of Vaporization

  • Evaporation of water requires a substantial amount of energy due to the high heat of vaporization of water.
  • Water has a heat of vaporization value of 40.65 kJ/mol.
  • A considerable amount of heat energy (586 calories) is required to accomplish this change in water.
  • As a result, water acts as a heat sink, or heat reservoir, and requires much more heat to boil than does a liquid such as ethanol (grain alcohol), whose hydrogen bonding with other ethanol molecules is weaker than water's hydrogen bonding.
  • Explain how heat of vaporization is related to the boiling point of water

• The First Law of Thermodynamics

  • "Thermo-" refers to heat, while "dynamics" refers to motion.
  • Conversely, in an exothermic reaction, the heat that is released in the reaction is given off and absorbed by the surroundings.
  • We know that chemical systems can either absorb heat from their surroundings, if the reaction is endothermic, or release heat to their surroundings, if the reaction is exothermic.
  • However, chemical reactions are often used to do work instead of just exchanging heat.
  • Another useful form of the first law of thermodynamics relates heat and work for the change in energy of the internal system:

• Logistic Population Growth

  • The formula we use to calculate logistic growth adds the carrying capacity as a moderating force in the growth rate.
  • Thus, population growth is greatly slowed in large populations by the carrying capacity K.
  • In addition, the accumulation of waste products can reduce an environment's carrying capacity.
  • In both examples, the population size exceeds the carrying capacity for short periods of time and then falls below the carrying capacity afterwards.
  • This fluctuation in population size continues to occur as the population oscillates around its carrying capacity.

• Homeostasis: Thermoregulation

  • 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.
  • Radiation is the emission of electromagnetic "heat" waves.
  • Heat radiates from the sun and from dry skin the same manner.
  • When a mammal sweats, evaporation removes heat from a surface with a liquid.
  • Convection currents of air remove heat from the surface of dry skin as the air passes over it.

• Activation Energy

  • The source of the activation energy needed to push reactions forward is typically heat energy from the surroundings.
  • For this reason, heating up a system will cause chemical reactants within that system to react more frequently.
  • Once reactants have absorbed enough heat energy from their surroundings to reach the transition state, the reaction will proceed.
  • Like these reactions outside of cells, the activation energy for most cellular reactions is too high for heat energy to overcome at efficient rates.
  • This figure implies that the activation energy is in the form of heat energy.

• Characteristics of Reptiles

  • Reptiles are ectotherms: animals whose main source of body heat comes from the environment .
  • This is in contrast to endotherms, which use heat produced by metabolism to regulate body temperature.
  • The advantage of ectothermy is that metabolic energy from food is not required to heat the body; therefore, reptiles can survive on about 10 percent of the calories required by a similarly-sized endotherm.
  • Reptiles, such as these sunbathing Florida redbelly turtles, are ectotherms: they rely on their environment for body heat.

• The Second Law of Thermodynamics

  • In most cases, this energy is in the form of heat.
  • This friction heats the air by temporarily increasing the speed of air molecules.
  • Likewise, some energy is lost in the form of heat during cellular metabolic reactions.
  • This is good for warm-blooded creatures like us because heat energy helps to maintain our body temperature.
  • That energy has been lost to the environment, usually in the form of heat.