1. Unit 2, Lesson 5: Phase Changes and Formulae

2. Temperature and Phase Changes
Note how temperature is constant during phase changes. Also note melting/freezing point and boiling/condensation point. – 5 min

3. Kinetic Energy of Molecules
Kinetic energy (KE) is the energy that molecules possess as a result of their motion.
There are three types:
Rotational energy causes a molecule to rotate around one of its bond axes.
Vibrational energy changes the bond lengths and/or angles between bonds in a molecule.
Translational energy causes the molecule to travel in a straight line from place to place.
Use Demo 11.III.19 to illustrate while you go through these notes. – 10 min

4. Putting It All Together
1. The molecules possess increasing amounts of vibrational and translational energy. 2. and 4. Translational energy reaches a critical value, allowing molecules to break out of their current phase.
3. and 5. All three types of KE steadily increase, but greatest increase is in translational.

5. Brain Break!

6. Types of Ions An anion is an ion with a negative charge.
A cation is an ion with a positive charge.

7. Constructing the Formula of an Ionic Compound
An ionic compound is a compound made up of ions. Writing its formula takes 3 steps:
Write the formula for the positive ion first and the negative ion second.
Criss-cross the numbers from the ion charges.
Tidy up the formulae (remove charges, divide both numbers by a common denominator if possible, and remove any 1s).
Use tin(IV) oxide as an example while going through the steps – 10 min

8. Now You Try! Write the formula for each of the following:
Potassium oxide
Tin(IV) sulphate
Ammonium phosphate
10 min

9. Homework: On phase changes: pg. 61 #60-61 and pg. 64 #65, 66, and 68
On writing formulae: pg. 71 #4 (a, c, e, etc.)
5 min