The triple point of a substance is the temperature and pressure at which the substance exists as which of the following?
A.
Simultaneously in sol, gel, and plasma phases
B.
As a gel with solid and liquid trapped in gas
C.
As a sol with gas and solid trapped in liquid
D.
Simultaneously in solid, liquid, and gas phases
The correct answer and Explanation is :
The correct answer is:
D. Simultaneously in solid, liquid, and gas phases
The triple point of a substance is a thermodynamic state where the substance exists in three phases—solid, liquid, and gas—simultaneously and in equilibrium. This means that at the specific temperature and pressure of the triple point, the three phases of the substance coexist in a stable manner.
To understand why this occurs, consider the phase diagram of a substance. A phase diagram plots the phases of a substance as a function of temperature and pressure. The triple point is a unique point on this diagram where the lines of equilibrium between the three phases (solid-liquid, liquid-gas, and solid-gas) intersect. At this point, the conditions are such that the energy and molecular arrangement allow all three phases to be present and stable at the same time.
For instance, water has a well-known triple point at 0.01°C (273.16 K) and 611.657 pascals. At this specific temperature and pressure, ice (solid), liquid water, and water vapor (gas) are all present and stable.
The significance of the triple point extends beyond just a curiosity of thermodynamics. It provides a reference point for calibrating thermometers and defining the Kelvin scale. The triple point of a substance can be used to precisely define the temperature scale because it is a fundamental and reproducible state.
In practical terms, this means that if you have a container with water at the triple point conditions, you will observe ice, liquid water, and water vapor coexisting. Any deviation in temperature or pressure from the triple point will result in a change in phase distribution, as the system will no longer be at equilibrium among all three phases.
Thus, the triple point is a fundamental concept in thermodynamics and phase transitions, illustrating the intricate balance of forces and conditions that allow for the coexistence of multiple phases of a substance.