Ocean vents are found at a wide range of depths; for example, vents at
30 m are found off the coast of New Zealand, and the deep-sea vents are
found at 3600 m. To the great surprise of the scientists, the vents were
found to contain life. The vents are rich sources of not only minerals but
also heat and are surrounded by a rich variety of organisms. There is
extreme pressure at the deep-sea vents; for example, a tube worm at
a vent 2500 m below sea level experiences a pressure of approximately
250 atm, which is enough to collapse most objects, but the physiology of
the organisms at the vents allows them to thrive.
Temperature
Temperature is usually thought of in terms of how hot or cold an object
is, but in thermodynamics temperature is a measure of molecular motion.
Consider how temperature is changed due to the presence of a source of
heat. An electric heater gets hot when a current – that is, electrons – flows
through a heating coil. The electrons lose the energy that had been pro-
vided by the voltage source, for example a battery, due to the resistance of
the heating coil. Since no work is being done (the coil is not moving) the
energy of the electrons is lost by converting the electrical energy into heat.
Light generated by a fire or the sun is absorbed by an object causing elec-
trons to change their relative position (orbital) around the nucleus in atoms.
The electrons can return to their initial state only by releasing the energy
as a vibration or heat.
Temperature is usually measured relative to certain physical processes.
The most common temperature scale is the Celsius scale (°C), which is derived
by assigning a value of 0°C to the temperature at which water freezes and
100°C to the temperature at which water boils, when the pressure is at
atmospheric pressure. In some countries, including the USA, the Fahrenheit
scale is still used. For this scale, a temperature of 100°F was originally
assigned to body temperature but this was later corrected to 98.6°F.
Materials can have either negative or positive temperatures on the Celsius
scale. For thermodynamics, the preferred scale is the Kelvin scale (K), in
which the temperature is always positive. The temperature in Celsius can
be converted into the temperature in Kelvin by adding the value of 273.15:
Temperature (K) =temperature (°C) +273.15 (1.11)
A critical concept of temperature is sometimes referred to as the “zeroth
law” of thermodynamics. If two objects are separated and at different
temperatures, the temperatures will become equal if they come into con-
tact with each other and a sufficient time has passed. The equilibration
of temperature arises because heat will pass from the hotter object to the
cooler object until there is no net flow when the two temperatures are
the same.