1. Melting Point and Boiling Points of Ionic and Covalent Compounds
According to Kinetic Molecular Theory
Particles in solids vibrate
As temperature increases, vibration increases
If the particles gain enough kinetic energy they can break apart from neighbouring particles
When particles have enough energy to break away, the melting point has been reached
Higher melting point – attraction between particles is higher.

2. Boiling Point and Kinetic Molecular Theory
In liquids, particles have enough energy to break away from neighbouring particles, but they are attracted to other particles
At the boiling point – particles have enough kinetic energy to break away from all other particles and become a gas.
High boiling point – forces b/n particles are strong
Low boiling point – forces b/n particles are weak

3. Melting Points and Boiling Points
Compound
Melting Point (°C)
Boiling Point (°C)
ethanol , C2H5OH
-114
+78.3
ammonia, NH3
-77.7
-33.3
cesium bromide, CsBr
+636
+1300
hydrogen, H2
-259
-253
hydrogen chloride, HCl
-85
magnesium oxide, MgO
+2825
+3600
methane, CH4
-182
-161
nitrogen, N2
-210
-196
sodium chloride, NaCl
+801
+1465
water, H2O
+100
Classify each into 1 of 3 categories: Low, intermediate or high boiling point.

4. Melting Points and Boiling Points
Compound
Melting Point (°C)
Boiling Point (°C)
ethanol , C2H5OH
-114
+78.3
ammonia, NH3
-77.7
-33.3
cesium bromide, CsBr
+636
+1300
hydrogen, H2
-259
-253
hydrogen chloride, HCl
-85
magnesium oxide, MgO
+2825
+3600
methane, CH4
-182
-161
nitrogen, N2
-210
-196
sodium chloride, NaCl
+801
+1465
water, H2O
+100
Classify the bonds in each of the molecules as covalent, polar covalent or ionic.

5. How is bond type related to boiling point?
Look at the results of your 2 lists.
How do they compare?
What does this tell you about the relative bond strength of each type of bond?
Explain your results by referring to the Kinetic Molecular Theory

6. Types of Forces Between Particles
Attractive Electrostatic Forces – occur b/n ions of opposite charge  they are strong
Dipole-dipole Forces – occur between the positive end of one molecule and the negative end of another  happens in polar molecules  weak
London Dispersion Forces – occur between any 2 molecules. Caused by the random movement of electrons...this creates temporary dipoles  very weak