Unit 9 Solution Chemistry

H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl Pour liquid between 2 beakers along with this slide. Is this evaporating? What does evaporating look like, in terms of these molecules? Is this evaporating very fast? Why? H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl

H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl d+ d- H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl

d+ d- H Cl H Cl H H Cl Cl H Cl H Cl H Cl H H Cl

d+ d- H Cl

d+ d- H Cl

Intermolecular Forces Attraction forces between molecules

Intramolecular Force Intermolecular Force Ionic bond Covalent bond Polar covalent bond Hold together ATOMS Breaking = chemical reaction Dipole-dipole London forces Hydrogen bond Hold together MOLECULES Breaking = phase change, dissolving

A. Dipole-dipole molecule must be ______________ (molecules with polar covalent bonds are not necessarily polar) d- side of the molecule is attracted to the d+ side can be intramolecular as well polar Non-polar Polar

Practice: Which of the following molecules are polar?   CH4 H2O NH3 

Br Show a bottle of liquid Br2

Dipole moment - - - d- d+ - - - - - - London force

Hmmmm…. Which of the following molecules can have London forces? MgO H2S CH4 C6H14 All of the above

Consider This: Why is chlorine a gas at room temperature, but bromine a liquid?

Sample Question Which of the following molecules has the strongest (or biggest) London force? MgO H2S CH4 C6H14 All of the above have the same amount

B. London Forces a momentary dipole temporary dipole molecule is non polar or polar weak and short-lived attractive force caused by _______________________ recall e- distribution is described as a probability at any given point in time, the distribution might be uneven, creating a ____________________on the molecule Increases with increasing #e- and size of the molecule a momentary dipole temporary dipole

C. Hydrogen Bonds molecule contains an H atom bonded to a very electronegative atom (_____, _____, ____) the H atom of one molecule is attracted to the F, O, or N on another molecule F O N

C. Hydrogen Bonds molecule contains an H atom bonded to a very electronegative atom (_____, _____, ____) the H atom of one molecule is attracted to the F, O, or N on another molecule the strongest of the intermolecular forces H has no e- to get in the way of its attraction to F, O, or N F O N

H – F H – F What would be something that would get in the way of intermolecular forces?

H – F H – F

Example: Which of the following molecules can hydrogen bond? HCN H2O H2S HF

Arrange water molecules to reflect the structure of ice.

Melting Point Boiling Point

d+ d- d- d+ d+ d+ d+ d+ d+ nail polish remover rubbing alcohol hexane d+ d+ d+ d+ d+ d+ d+ d- d- d- d- d- d- d+ d+ d+ d+ d+ d+ d+

broken more stronger higher larger mass higher Intermolecular bonds are responsible for how readily covalent substances undergo physical changes Intermolecular forces must be _____________ The ____________ intermolecular forces present, and the ______________ that they are, the ______________ the melting and boiling points The _______________ the molecule and the higher the ________________, the _____________ the boiling point. broken more stronger higher larger mass higher

Example: Among H2O, CO2, and H2S, explain why H2O has the highest boiling point at 100C, followed by H2S at -60.33C, then CO2 at-78.44C