![density of water at room temperature density of water at room temperature](https://cdn.pmnewsnigeria.com/wp-content/uploads/2024/02/cb9bd9d1-4515-450c-bdfa-cbbd7595e9b1_1200-636x339.jpg)
Supercritical CO 2 is pumped into oil wells that are no longer producing much oil to dissolve the residual oil in the underground reservoirs. Because many substances are quite soluble in supercritical CO 2, commercial processes that use it as a solvent are now well established in the oil industry, the food industry, and others. For example, carbon dioxide has a low critical temperature (31☌), a comparatively low critical pressure (73 atm), and low toxicity, making it easy to contain and relatively safe to manipulate. In the last few years, supercritical fluids have evolved from laboratory curiosities to substances with important commercial applications. Above T c, a dense homogeneous fluid fills the tube. At the critical temperature, the meniscus disappears because the density of the vapor is equal to the density of the liquid. Below the critical temperature the meniscus between the liquid and gas phases is apparent. At the critical temperature, the meniscus separating the liquid and gas phases disappears.įigure 11.6.1 Supercritical fluids Professor Martyn Poliakoff demonstrates supercritical fluids. The transition between a liquid/gas mixture and a supercritical phase is demonstrated for a sample of chlorine in Figure 11.6.1. For example, the density of water at its critical point ( T = 374☌, P = 217.7 atm) is 0.32 g/mL, about one-third that of liquid water at room temperature but much greater than that of water vapor under most conditions.
![density of water at room temperature density of water at room temperature](https://scrn-cdn.omnicalculator.com/physics/water-density@2.png)
This single phase is called a supercritical fluid The single, dense fluid phase that exists above the critical temperature of a substance., which exhibits many of the properties of a gas but has a density more typical of a liquid. At the critical point, the liquid and gas phases have exactly the same density, and only a single phase exists. As the pressure of a gas increases, its density increases. As the temperature of a liquid increases, its density decreases. To understand what happens at the critical point, consider the effects of temperature and pressure on the densities of liquids and gases, respectively. The critical temperatures and pressures of several common substances are listed in Table 11.6.1. The combination of critical temperature and critical pressure is called the critical point. Each substance also has a critical pressure ( P c), the minimum pressure needed to liquefy it at the critical temperature. Conversely, substances with weak intermolecular interactions have relatively low critical temperatures. Substances with strong intermolecular forces tend to form a liquid phase over a very large temperature range and therefore have high critical temperatures. Instead, the substance forms a single phase that completely occupies the volume of the container. Above the critical temperature, the molecules have too much kinetic energy for the intermolecular attractive forces to hold them together in a separate liquid phase. This temperature is the critical temperature ( T c), the highest temperature at which a substance can exist as a liquid. In fact, for every substance, there is some temperature above which the gas can no longer be liquefied, regardless of pressure. As we increase the temperature of a gas, liquefaction becomes more and more difficult because higher and higher pressures are required to overcome the increased kinetic energy of the molecules. In Section 11.1, we saw that a combination of high pressure and low temperature allows gases to be liquefied.