1. Properties

2. How can you determine if a compound is ionic or molecular?
Ionic compounds are formed by the attractions between oppositely charged ions. (metal + nonmetal or complex ion)
Molecular compounds are formed when nonmetallic atoms share attractions for each other's electrons.
Due to their different ways of bonding, each class of compounds has its own unique properties.

3. By performing some simple tests, it is possible to classify a compound as either ionic or molecular. These simple tests include:
state of matter
melting point
solubility in water
electrical conductivity.

4. A physical property refers to any characteristic such as colour, solubility, electrical conductivity, melting point, etc.
For example: The physical properties of table salt include; white solid at room temperature, cubic crystal structure, high melting point, soluble in water, and conducts electricity when in solution (dissolved in water).

5. A physical change refers to a change in the characteristics of matter when there is a change in its physical environment.
For example, ice (solid water) will melt to form liquid water when heated. This change in the physical state of matter is an example of a physical change.
During a physical change the atoms that make up the compound are not rearranged in any manner

6. Chemists use symbols to represent states of matter.
For example: water has three physical states of matter - solid, liquid and gas. Can you predict the meaning of the following: H2O (s),  H2O (l),  H2O (g) 

7. A chemical property refers to the behaviour of matter during a chemical reaction.
During a chemical reaction there is a chemical change,
atoms are rearranged to form new substances, new types of matter with new chemical properties are formed as products.
For example: Water can be decomposed into hydrogen and oxygen gas when electricity is passed through it. Since hydrogen and oxygen have totally different physical and chemical properties than water, this is an example of a chemical change or chemical reaction.
We will learn more on chemical change in the next section after the test

8. physical properties to classify compounds as ionic or molecular.
The state of matter refers to matter as either solid, liquid, or gas. 
Ionic compounds are solids at room temperature
molecular substances as a group are variable in their states of matter - some are solids, but many are liquids or gases.
Since all ionic compounds are solids, you can classify any pure liquid or gas substance as molecular. 
Your turn! Alcohol (a liquid at room temperature) has the formula CH3CH2OH. Is alcohol ionic or molecular? How do you know?

9. Melting Point:
Generally, molecular substances like sugar melt at temperatures below 300°C,
whereas ionic substances tend to have melting points above 300°C.
However, melting point data alone is usually insufficient evidence to classify a substance as ionic or molecular.
In general, molecular compounds tend to have low melting points compared to the very high melting points of ionic compounds.

10. NaCl(aq) - sodium chloride dissolved in water.
Solubility in Water :
Now let's consider solubility of solids (which by now you recognize may be either ionic or molecular) in water.
When a substance dissolves in water it forms what is known as an aqueous solution.(aq)
In chemical equations, chemists use the symbol (aq) to the lower right of the symbol or formula to represent an aqueous solution.
aqueous solution - a solution in which water is the solvent.
table sugar, C12H22O11,(molecular compound)  dissolve it in pure water and there you have it; aqueous solution
Another example: Place some table salt (NaCl) (ionic compound) in water and you have another example of an aqueous solution - salt water!
NaCl(aq) - sodium chloride dissolved in water.
Both ionic and molecular compounds may or may not dissolve in water, so this evidence alone cannot be used to classify a solid compound.

11. Electrical Conductivity - (Electrical Conductivity Test of Aqueous Solutions)
When solubility in water is combined with an electrical conductivity test we have an excellent way of classifying solids as either ionic or molecular.
In our examples, both sugar and salt are soluble in water. How can we determine which is ionic and which is molecular? We build a conductivity tester and use it to find our answer!
A simple conductivity tester can be made using some wire, two metal rods (nails or paper clips), a battery, a light bulb, and light bulb socket.
In order for electricity to flow it needs a path to follow.  The idea behind the electrical conductivity test is that free ions in the solution offer a path for the movement of electrons.  Thus any solutions containing ions will conduct electricity.
Ionic compounds are composed of ions.  When dissolved in water the ionic compounds break up into its ions to form electrically conductive solutions (electrolytic solutions).
Molecular compounds are composed of neutral molecules.  When dissolved in water they stay as neutral molecules.  Molecules do not allow the movement of electrons, thus do not conduct electricity. (nonelectrolytic solutions),  (except for molecular acids which we will look at in the next lesson)
To determine if the substance is a molecular acid, test the pH of the solution. If it is neutral (ph = 7) then it is not a molecular acid. 

12. an image showing two beakers, each being tested using our home made conductivity tester. One beaker contains an aqueous solution of table salt. The second beaker contains an aqueous solution of table sugar. Examine the image and identify which beaker contains the salt (an ionic compound) and which beaker contains the sugar (a molecular compound).  (Is it the beaker on the left, or the beaker on the right? How do you know?)

13. Table 1: Properties of Ionic and Molecular Compounds
Ionic
Molecular
Composition
composed of ions: metal, nonmetal, or a combination involving a complex (polyatomic) ion
composed of two nonmetal atoms
Electrical Conductivity
very good when dissolved in water or  in the molten or liquid state
poor to nonconductive
Melting Point
generally higher than 300°C
generally lower than 300°C
Solubility in Water
variable; many ionic compounds dissolve in water, but some are insoluble. Ionic solutions are electrically conductive. Some ionic solutions have characteristic colours.
variable; those that dissolve in water generally do not form electrically conductive solutions (exception: molecular acids)
Bonding
ionic bonds due to a transfer of valence  electrons.
covalent bonding due to the sharing of valence electrons