5_PropertiesOfLiquidsAndSolids(S)

5_PropertiesOfLiquidsAndSolids(S) - Properties of Liquids...

Info icon This preview shows pages 1–13. Sign up to view the full content.

View Full Document Right Arrow Icon
CHEM 1000 3.0 Structure of liquids and solids 1 Properties of Liquids and Solids •Petrucci, Herring Madura and Bissonnette : Chapter 12
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
CHEM 1000 3.0 Structure of liquids and solids 2 Van der Waal Forces In the section on gases we said there were forces between the molecules. Now we know more about bonding and electronic structure we can revisit the question. What kinds of forces exist between molecules?
Image of page 2
CHEM 1000 3.0 Structure of liquids and solids 3 Van der Waal Forces Van der Waal forces are those attractive forces between molecules that are responsible for: Real gas behaviour (Van der Waal “a”) – Condensation There are a number of such forces resulting in different strengths of interactions between molecules.
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
CHEM 1000 3.0 Structure of liquids and solids 4 Van der Waal Forces London or Dispersion Force The quantum concept of electronic structure talks about the probability of an electron being in a certain region at a certain time. Even for an atom or a perfectly symmetrical molecule there is a finite chance that the electronic charges are not uniformly distributed. This produces an instantaneous dipole .
Image of page 4
CHEM 1000 3.0 Structure of liquids and solids 5 Van der Waal Forces London or Dispersion Force The instantaneous dipole can then influence neighbouring molecules and induce a dipole in them. (an induced dipole ) This gives two dipoles that can attract. This is usually called a dispersion force or a London force . Molecule on average Instantaneous dipole
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
CHEM 1000 3.0 Structure of liquids and solids 6 Van der Waal Forces London or Dispersion Force a. Normal b. Instantaneous dipole c. Instantaneous dipole (left) induced dipole (right)
Image of page 6
CHEM 1000 3.0 Structure of liquids and solids 7 Van der Waal Forces London or Dispersion Force This force is going to be strongest in a molecule with a large number of electrons or for an elongated molecule. The ability or tendency of a molecule to have charge separation occur is called polarizability . The effect of London forces can often be seen in the boiling points of similar compounds.
Image of page 7

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
CHEM 1000 3.0 Structure of liquids and solids 8 Effect of London Forces Bpt(He) = 4K Bpt(Rn) = 211K Rn is larger ____________________________________ n-pentane is more elongated CH 3 -CH 2 -CH 2 -CH 2 -CH 3 Bpt 36.1 o C Bpt 9.5 o C C C H 3 CH 3 CH 3 CH 3
Image of page 8
CHEM 1000 3.0 Structure of liquids and solids 9 Van der Waal Forces Dipole-Dipole interactions Bonds where the elements have different electronegativity have a permanent charge separation. E.g. HCl H Cl If this shows up in the molecule we say the molecule has a permanent dipole.
Image of page 9

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
CHEM 1000 3.0 Structure of liquids and solids 10 Van der Waal Forces Dipole-Dipole interactions For molecules with permanent dipoles, Dipole-Dipole interactions can occur.
Image of page 10
CHEM 1000 3.0 Structure of liquids and solids 11 Van der Waal Forces Dipole-Dipole interactions
Image of page 11

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
CHEM 1000 3.0 Structure of liquids and solids 12 Van der Waal Forces Dipole-Dipole interactions Dipole-dipole interactions are in addition to the London forces.
Image of page 12
Image of page 13
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern