Textbook Notes (369,072)
Canada (162,367)
Chemistry (276)
CHMB20H3 (5)
Chapter 4

CHMB20 Chapter 4

3 Pages
157 Views

Department
Chemistry
Course Code
CHMB20H3
Professor
Jamie Donaldson

This preview shows page 1. Sign up to view the full 3 pages of the document.
Description
Chapter 4: Physical Transformations Of Pure Substances Phase Diagrams • Phase: form of matter that is uniform throughout in chemical composition and physical state. • Phase Transition: the spontaneous conversion of one phase into another and may be studied by techniques that include thermal analysis. o Transition Temperature (Ttrs): the temperature at which the two phases are in equilibrium and Gibbs energy of the system is minimized at the prevailing pressure. o Thermal Analysis: the transition is detected by noting that the temperature does not change even though heat is being supplied or removed from the sample. o Metastable Phases: thermodynamically unstable phases that persist because the transition is kinetically hindered. • The thermodynamic analysis of phases is based on the fact that at equilibrium, the chemical potential of a substance is the same throughout the sample, regardless of how many phases are present. o Chemical Potential (μ ): measure of the potential that a substance has for undergoing change in a system and is synonyms with molar Gibbs energy (μ = Gm). o At equilibrium, μ 1 = μ 2 and then, there is no change in G. • A susbtance characterized by a variety of parameters that can be identified on its phase diagram. o Phase Diagram: shows the regions of pressure and temperature at which its various phases are thermodynamically stable. o Phase Boundaries: the lines separating the regions that show the values of p and T at which two phases coexist in equilibrium and their chemical potentials are equal. o Vapor Pressure: the pressure of a vapor in equilibrium with the liquid. o Sublimation Vapor Pressure: the vapor pressure of the solid phase. o The vapor pressure of a substance increases with temperature because at higher temperatures, more molecules have enough energy to escape from their neighbors. o Boiling: the condition of free vaporization throughout the liquid. o Boiling Temperature: the temperature at which the vapor pressure of a liquid is equal to the external pressure.  At normal boiling point, temperature where external pressure is 1 atm.  At standard boiling point, temperature where vapor pressure is 1 bar. o Critical Temperature (Tc): temperature at which the surface disappears. o Critical Pressure (pc): vapor pressure at the critical temperature. o Supercritical Fluid: a single uniform phase at and above the critical temperature. o Melting Temperature: the temperature at which the liquid and solid phases of a substance coexist in equilibrium. o Freezing Temperature: because a substance melts at exactly the same temperature as it freezes, melting temperature is the same as its freezing temperature.  Normal Freezing Point (Tf): freezing temperature when pressure is 1 atm.  Standard Freezing Point (Ts): freezing point when pressure is 1 bar. o Triple Point: a point at which the three phase boundaries meet; it occurs at a single definite pressure and temperature characteristic of the substance. o If the slope of the solid-liquid phase boundary is shown, then the triple point also marks the lowest temperature at which the liquid can exist; the critical temperature is the upper limit. • The phase rule relates the number of variables that may be changed while the phases of a system remain in mutual equilibrium. o Phase Rule: F = C – P + 2, where F is the variance, C is the number of components and P is the number of phases at equilibrium. o Component: chemically independent constituent of a system; the minimum number of types of independent species necessary to define the composition of all the phases present in the system. o Constituent: a chemical species that is present.  A mixture of ethanol and water has two constituents.  A solution of sodium chloride has three constituents; Na+, Cl- and H2O. o Variance: the number of intensive variables that can b
More Less
Unlock Document

Only page 1 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit