heat of vaporization

Examples of heat of vaporization in the following topics:

• Water’s Heat of Vaporization

  • Evaporation of water requires a substantial amount of energy due to the high heat of vaporization of water.
  • As a result of the network of hydrogen bonding present between water molecules, a high input of energy is required to transform one gram of liquid water into water vapor, an energy requirement called the heat of vaporization.
  • Water has a heat of vaporization value of 40.65 kJ/mol.
  • They depend only on the vapor pressure of water.
  • Explain how heat of vaporization is related to the boiling point of water

• Causes of Global Climate Change

  • The gases and solids released by volcanic eruptions can include carbon dioxide, water vapor, sulfur dioxide, hydrogen sulfide, hydrogen, and carbon monoxide.
  • When heat energy from the sun strikes the earth, gases known as greenhouse gases trap the heat in the atmosphere, similar to how the glass panes of a greenhouse keep heat from escaping.
  • The greenhouse gases that affect earth include carbon dioxide, methane, water vapor, nitrous oxide, and ozone.
  • Another source of methane is the melting of clathrates: frozen chunks of ice and methane found at the bottom of the ocean.
  • This is an example of the positive feedback loop that is leading to the rapid rate of increase of global temperatures.

• Water’s High Heat Capacity

  • The high heat capacity of water has many uses.
  • The heat is quickly transferred to a pool of water to cool the reactor.
  • 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.

• Water’s States: Gas, Liquid, and Solid

  • The orientation of hydrogen bonds as water changes states dictates the properties of water in its gaseous, liquid, and solid forms.
  • The formation of hydrogen bonds is an important quality of liquid water that is crucial to life as we know it.
  • The breaking of these bonds is caused by the motion (kinetic energy) of the water molecules due to the heat contained in the system.
  • When the heat is raised as water is boiled, the higher kinetic energy of the water molecules causes the hydrogen bonds to break completely and allows water molecules to escape into the air as gas (steam or water vapor).
  • The low density of ice , an anomaly, causes it to float at the surface of liquid water, such as an iceberg or the ice cubes in a glass of water.

• Biogeochemical Cycles

  • Energy flows directionally through ecosystems, entering as sunlight (or inorganic molecules for chemoautotrophs) and leaving as heat during the many transfers between trophic levels.
  • The components of organic molecules are constantly being stored and recycled as part of their biogeochemical cycle.
  • Water can be liquid on the surface and beneath the surface or frozen (rivers, lakes, oceans, groundwater, polar ice caps, and glaciers) or exist as water vapor in the atmosphere .
  • The cycling of all of these elements is interconnected.
  • For example, the movement of water is critical for the leaching of nitrogen and phosphate into rivers, lakes, and oceans.

• Heat Conservation and Dissipation

  • Animals conserve or dissipate heat in a variety of ways.
  • Mammals use layers of fat to achieve the same end; the loss of significant amounts of body fat will compromise an individual's ability to conserve heat.
  • When muscles are contracted, most of the energy from the ATP used in muscle actions is wasted energy that translates into heat.
  • In cases of severe cold, a shivering reflex is activated that generates heat for the body.
  • Many species also have a type of adipose tissue called brown fat that specializes in generating heat.

• The First Law of Thermodynamics

  • Thermodynamics is the study of heat energy and other types of energy, such as work, and the various ways energy is transferred within chemical systems.
  • "Thermo-" refers to heat, while "dynamics" refers to motion.
  • However, chemical reactions are often used to do work instead of just exchanging heat.
  • If you've ever witnessed a video of a space shuttle lifting off, the chemical reaction that occurs also releases tremendous amounts of heat and light.
  • Another useful form of the first law of thermodynamics relates heat and work for the change in energy of the internal system:

• The Water (Hydrologic) Cycle

  • Water is the basis of all living processes.
  • More than half of the human body is made up of water, while human cells are more than 70 percent water.
  • However, when examining the stores of water on earth, 97.5 percent of it is non-potable salt water.
  • This leads to the evaporation (water to water vapor) of liquid surface water and the sublimation (ice to water vapor) of frozen water, which deposits large amounts of water vapor into the atmosphere.
  • Over time, this water vapor condenses into clouds as liquid or frozen droplets, which is eventually followed by precipitation (rain or snow), returning water to the earth's surface.

• Homeostasis: Thermoregulation

  • Endotherms create most of their heat via metabolic processes, and are colloquially referred to as "warm-blooded."
  • An ectotherm, from the Greek (ektós) "outside" and (thermós) "hot," is an organism in which internal physiological sources of heat are of relatively small or quite negligible importance in controlling body temperature.
  • 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.
  • Convection currents of air remove heat from the surface of dry skin as the air passes over it.

• Gas Pressure and Respiration

  • Air is a mixture of gases: primarily nitrogen (N2; 78.6 percent), oxygen (O2; 20.9 percent), water vapor (H2O; 0.5 percent), and carbon dioxide (CO2; 0.04 percent).
  • Each gas component of that mixture exerts a pressure.
  • Approximately 21 percent of atmospheric gas is oxygen.
  • Patm, the atmospheric pressure, is the sum of all of the partial pressures of the atmospheric gases added together: Patm = PN2 + PO2 + PH2O + PCO2= 760 mm Hg.
  • The pressure of the water vapor in the lung does not change the pressure of the air, but it must be included in the partial pressure equation.