KaiserScience

Home » Chemistry » Triple point

Triple point

Start here

The following is from the Learner.Org Chemistry course https://www.learner.org/courses/chemistry/about/about.html

Once the gas laws were formulated, chemists could analyze how materials transitioned from one phase to another, and how temperature and pressure affected these changes.

In 1897, a British metallurgist named Sir William Chandler Roberts-Austen (1843–1902) produced what is widely regarded as an early form of a now-common tool in chemistry and related disciplines: the phase diagram.

Modern phase diagrams show relationships between different states of matter under various combinations of temperature and pressure.

A substance can exist in two different states at once—for example, as a liquid and a gas, with molecules cycling from one state to the other.

It is also possible for a material to be both solid and liquid, with both melting and freezing taking place at its edges, or to exist as a solid and a gas.

Phase diagrams show what forms a substance will take under given temperatures and pressure levels, and where these equilibrium lines (when equal numbers of molecules are changing form in both directions) are located. (Figure 2-11)

Figure 2-11. Generic Phase Diagram for a Single Substance © Science Media Group. https://www.learner.org/courses/chemistry/text/text.html?dis=U&num=Ym5WdElUQS9NeW89&sec=YzJWaklUQS9OeW89

Figure 2-11. Generic Phase Diagram for a Single Substance
© Science Media Group.
https://www.learner.org/courses/chemistry/text/text.html?dis=U&num=Ym5WdElUQS9NeW89&sec=YzJWaklUQS9OeW89

Amazing: See a flask of liquid cyclohexane brought to the brink of its triple-point:
suddenly it can boil and freeze at the same time.

http://physicsfootnotes.com/triple-point/

A volumetric flask containing liquid cyclohexane is depressurized to a very low pressure by a turbo-molecular vacuum pump. The rapid drop in pressure results in a rapid drop in temperature, causing the substance to temporarily freeze, but the system is unstable, flirting with the triple point (a point of pressure and temperature at which a substance is simultaneously solid, liquid, and gas). The result is a fluctuation between all three states of matter, in a spectacular display of chemistry and physics in action.

http://physicsfootnotes.com/triple-point/

 

 

Advertisements
%d bloggers like this: