Could someone please explain supercritical fluid to me?

Question

Could someone please explain this to me in laymans terms??? I don't understand it and I need to know it for my chem class.

Answer 1

I'll try it in laymen's terms:

supercritical fluid is a phase of matter (just like gas, liquid and solid). This happens after gas when either the pressure is above the critical pressure *or* the temperature is above the critical temperature.

Supercritical fluid has certain properties. It cannot be compressed back to a liquid no matter how much pressure you apply for example. It also behaves in some ways like a gas and in some ways like a liquid.

Answer 2

Hope this helps some............

A supercritical fluid is a material which can be either liquid or gas, used in a state above the critical temperature and critical pressure where gases and liquids can coexist. It shows unique properties that are different from those of either gases or liquids under standard conditions.
A supercritical fluid has both the gaseous property of being able to penetrate anything, and the liquid property of being able to dissolve materials into their components? In addition, it offers the advantage of being able to change density to a great extent in a continuous manner. On this account, use of carbon dioxide or water in the form of a supercritical fluid offers a substitute for an organic solvent in the fields of the food industry and medical supplies. Furthermore, as a new technology which is user-friendly to both human beings and the environment, it is attracting wide attention.

Answer 3

A supercritical fluid is any substance at a temperature and pressure above its thermodynamic critical point. It has the unique ability to diffuse through solids like a gas, and dissolve materials like a liquid. Additionally, it can readily change in density upon minor changes in temperature or pressure. These properties make it suitable as a substitute for organic solvents in a process called Supercritical Fluid Extraction. Carbon dioxide and water are the most commonly used supercritical fluids.

For engineering purposes, supercritical fluids can be regarded as “hybrid solvents” with properties between those of gases and liquids, i.e. a solvent with a low viscosity, high diffusion rates and no surface tension. In the case of supercritical carbon dioxide, the viscosity is in the range of 20–100 µPa·s (0.02-0.1 cP), where liquids have viscosities of approximately 500–1000 µPa·s (0.5-1.0 cP) and gases approximately 10 µPa·s (0.01 cP), respectively. Diffusivities of solutes in supercritical carbon dioxide are up to a factor 10 higher than in liquid solvents. Additionally, these properties are strongly pressure-dependent in the vicinity of the critical point, making supercritical fluids highly tunable solvents. Of the components shown in Table 1, carbon dioxide and water are the most frequently used in a wide range of applications, including extractions, dry cleaning and chemical waste disposal. In polymer systems, ethylene and propylene are also widely used, where they act both as a solvent and as the reacting monomer.

One of the most important properties of Supercritical Gas Fluids is that their solvating properties are a complex function of their pressure and temperature, independant of their density. This means that (taking a very simplistic approach) raw materials containing CO2 soluble products can be selectively extracted or selectively precipitated to obtain ultra-pure extracts. Although the details are much more complex than this, it remains the dominant chemical-free technology for the production of decaffeinated coffee, nicotine-free tobacco, and many of the world's best spice extracts.