specific heat

Examples of specific heat in the following topics:

• Water’s High Heat Capacity

  • The high heat capacity of water has many uses.
  • The capability for a molecule to absorb heat energy is called heat capacity, which can be calculated by the equation shown in the figure .
  • Water has the highest specific heat capacity of any liquid.
  • Specific heat is defined as the amount of heat one gram of a substance must absorb or lose to change its temperature by one degree Celsius.
  • In fact, the specific heat capacity of water is about five times more than that of sand.

• Animal Bioenergetics

  • No energy system is one hundred percent efficient as an animal's metabolism produces waste energy in the form of heat.
  • If an animal can conserve that heat and maintain a relatively-constant body temperature, it is classified as a warm-blooded animal: an endotherm.
  • The insulation used to conserve the body heat comes in the forms of fur, fat, or feathers.
  • The absence of insulation in ectothermic animals increases their dependence on the environment for body heat.
  • The amount of energy expended by an animal over a specific time is called its metabolic rate.

• 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.

• Intracellular Hormone Receptors

  • The cell signaling pathways induced by the steroid hormones regulate specific genes within the cell's DNA.
  • In this way, the steroid hormone regulates specific cell processes .
  • The hormone-receptor complex stimulates transcription of specific genes in the same way that steroid hormones do.
  • An intracellular nuclear receptor (NR) is located in the cytoplasm bound to a heat shock protein (HSP).
  • Upon hormone binding, the receptor dissociates from the heat shock protein and translocates to the nucleus.

• Properties of Life

  • All organisms grow and develop following specific instructions coded for by their genes.
  • Organs (groups of tissues working together) perform specific functions, such as carrying oxygen throughout the body, removing wastes, delivering nutrients to every cell, and cooling the body.
  • Organisms that live in cold climates, such as the polar bear , have body structures that help them withstand low temperatures and conserve body heat.
  • In hot climates, organisms have methods (such as perspiration in humans or panting in dogs) that help them to shed excess body heat.
  • Polar bears (Ursus maritimus) and other mammals living in ice-covered regions maintain their body temperature by generating heat and reducing heat loss through thick fur and a dense layer of fat under their skin.

• 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

• Evolution of Birds

  • This course of evolution is suggested by similarities between theropod fossils and birds, specifically in the structure of the hip and wrist bones, as well as the presence of the wishbone, formed by the fusing of the clavicles.
  • Feathers provide insulation, but this is only beneficial if body heat is being produced internally.
  • Similarly, internal heat production is only viable if insulation is present to retain that heat.

• 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:

• Regulating Protein Activity and Longevity

  • A cell can rapidly change the levels of proteins in response to the environment by adding specific chemical groups to alter gene regulation.
  • Chemical modifications occur in response to external stimuli such as stress, the lack of nutrients, heat, or ultraviolet light exposure.
  • This is an efficient way for the cell to rapidly change the abundance levels of specific proteins in response to the environment.

• 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.