In northern climates it is common to have a layer of frost form on cars that hav

Question

In northern climates it is common to have a layer of frost form on cars that have been out overnight in the winter. During the day the frost disappears despite the temperature remaining below freezing. How? a) the frost melts due to the sun heating the surface of the car above the melting point B) the frost evaporates due to the sun heating the solid c) the frost cycles as does the saturation level of moisture in the winter air does from night to day The frost sublimes directly from solid ice to water vapor e) none of the above

Explanation / Answer

Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot. When a heat transfer path between them is open, heat spontaneously flows from bodies of a higher temperature to bodies of lower temperature. The flow rate increases with the temperature difference, while no heat will be exchanged between bodies of the same temperature, which are then said to be in "thermal equilibrium". In thermodynamics, in a system of which the entropy is considered as an independent externally controlled variable, absolute, or thermodynamic, temperature is defined as the derivative of the internal energy with respect to the entropy. In an ideal gas, the constituent molecules do not show internal excitations. They move according to Newton's first law of motion, freely and independently of one another, except during collisions that last for negligibly short times. The temperature of an ideal gas is proportional to the mean translational kinetic energy of its molecules. Quantitatively, temperature is measured with thermometers, which may be calibrated to a variety of temperature scales. Thermal vibration of a segment of protein alpha helix. The amplitude of the vibrations increases with temperature. Temperature plays an important role in all fields of natural science, including physics, geology, chemistry, atmospheric sciences and biology.Many physical properties of materials including the phase solid, liquid, gaseous or plasma, density, solubility, vapor pressure, and electrical conductivity depend on the temperature. Temperature also plays an important role in determining the rate and extent to which chemical reactions occur. This is one reason why the human body has several elaborate mechanisms for maintaining the temperature at 310 K, since temperatures only a few degrees higher can result in harmful reactions with serious consequences. Temperature also determines the thermal radiation emitted from a surface. One application of this effect is the incandescent light bulb, in which a tungsten filament is electrically heated to a temperature at which significant quantities of visible light are emitted. [edit]Temperature scales See also: Scale of temperature Much of the world uses the Celsius scale (°C) for most temperature measurements. It has the same incremental scaling as the Kelvin scale used by scientists, but fixes its null point, at 0°C = 273.15K, approximately the freezing point of water (at one atmosphere of pressure).[note 1] The United States uses the Fahrenheit scale for common purposes, a scale on which water freezes at 32 °F and boils at 212 °F (at one atmosphere of pressure). For practical purposes of scientific temperature measurement, the International System of Units (SI) defines a scale and unit for the thermodynamic temperature by using the easily reproducible temperature of the triple point of water as a second reference point. The reason for this choice is that, unlike the freezing and boiling point temperatures, the temperature at the triple point is independent of pressure (since the triple point is a fixed point on a two-dimensional plot of pressure vs. temperature). For historical reasons, the triple point temperature of water is fixed at 273.16 units of the measurement increment, which has been named the kelvin in honor of the Scottish physicist who first defined the scale. The unit symbol of the kelvin is K. Absolute zero is defined as a temperature of precisely 0 kelvins, which is equal to -273.15 °C or -459.67 °F. [edit]Thermodynamic approach to temperature Temperature is one of the principal quantities studied in the field of thermodynamics. Thermodynamics investigates the relation between heat and work, using a special scale of temperature called the absolute temperature, and thus relates temperature to work, as considered below. In thermodynamic terms, temperature is a macroscopic intensive variable because it is independent of the bulk amount of elementary entities contained inside, be they atoms, molecules, or electrons. Real world systems are often not in thermodynamic equilibrium and not homogeneous. For study by methods of classical irreversible thermodynamics, a body is usually spatially and temporally divided conceptually into imagined 'cells' of small size. If classical thermodynamic equilibrium conditions for matter are fulfilled to good approximation in each 'cell', then it is homogeneous and a temperature exists for it, and local thermodynamic equilibrium is said to prevail throughout the body. [edit]Statistical mechanics approach to temperature Statistical mechanics provides a microscopic explanation of temperature, based on macroscopic systems' being composed of many particles, such as molecules and ions of various species, the particles of a species being all alike. It explains macroscopic phenomena in terms of the mechanics of the molecules and ions, and statistical assessments of their joint adventures. In the statistical thermodynamic approach, degrees of freedom are used instead of particles. On the molecular level, temperature is the result of the motion of the particles that constitute the material. Moving particles carry kinetic energy. Temperature increases as this motion and the kinetic energy increase. The motion may be the translational motion of particles, or the energy of the particle due to molecular vibration or the excitation of an electron energy level. Although very specialized laboratory equipment is required to directly detect the translational thermal motions, thermal collisions by atoms or molecules with small particles suspended in a fluid produces Brownian motion that can be seen with an ordinary microscope. The thermal motions of atoms are very fast and temperatures close to absolute zero are required to directly observe them. For instance, when scientists at the NIST achieved a record-setting low temperature of 700 nK (1 nK = 10-9 K) in 1994, they used laser equipment to create an optical lattice to adiabatically cool caesium atoms. They then turned off the entrapment lasers and directly measured atom velocities of 7mm per second in order to calculate their temperature. Molecules, such as oxygen (O2), have more degrees of freedom than single spherical atoms: they undergo rotational and vibrational motions as well as translations. Heating results in an increase in temperature due to an increase in the average translational energy of the molecules. Heating will also cause, through equipartitioning, the energy associated with vibrational and rotational modes to increase. Thus a diatomic gas will require a higher energy input to increase its temperature by a certain amount, i.e. it will have a higher heat capacity than a monatomic gas. The process of cooling involves removing thermal energy from a system. When no more energy can be removed, the system is at absolute zero, which cannot be achieved experimentally. Absolute zero is the null point of the thermodynamic temperature scale, also called absolute temperature. If it were possible to cool a system to absolute zero, all motion of the particles comprising matter would cease and they would be at complete rest in this classical sense. Microscopically in the description of quantum mechanics, however, matter still has zero-point energy even at absolute zero, because of the uncertainty principle. [edit]Basic theory As distinct from a quantity of heat, temperature may be viewed as a measure of a quality of a body [1] or of heat.[2][3][4][5] The quality is called hotness by some writers.[6][7] When two systems are at the same temperature, no net heat transfer occurs spontanteously, by conduction or radiation, between them. When a temperature difference does exist, and there is a thermally conductive or radiative connection between them, there is spontaneous heat transfer from the warmer system to the colder system, until they are at mutual thermal equilibrium. Heat transfer occurs by conduction or by thermal radiation.[8][9][10][11][12][13][14][15] Experimental physicists, for example Galileo and Newton,[16] found that there are indefinitely many empirical temperature scales.

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