Key Area 1.4 - Properties

Question 1

What is an ionic compound (ionic lattice)

Answer 1

When metal and non metal atoms transfer their unpaired outer electrons from the metal atom to the non metal atom, a positively charged ion and negatively charged ion forms. The oppositely charged ions attract each other and form ionic bonds. Because the ions are charged they attract each other from all directions forming a giant lattic
Example, Sodium Chloride (Salt)

Question 2

What is a covalent substance

Answer 2

When 2 non metal atoms share their unpaired outer electrons by overlapping their electron clouds to form covalent bonds. The attraction form the 2 positive nuclei for the pair of shared electrons holds the atom together. If there is a fixed number of atoms in the structure, it is a covalent molecule. If the number of atoms is unlimited in the structure, it is a covalent network.
Example, molecular- Hydrogen Oxide
Network- Carbon Graphite or Silicon Oxide

Question 3

List the properties of an Ionic Lattice
Melting and boiling point?
State at room temperature?
Electrical conductivity?
Solubility in water?

Answer 3

List the properties of an Ionic Lattice
Melting and boiling point - HIGH
State at room temperature - SOLID
Electrical conductivity - WHEN MOLTEN OR SOLUTION 
Solubility in water - YES

Question 4

List the properties of a Covalent Network
Melting and boiling point?
State at room temperature?
Electrical conductivity?
Solubility in water?

Answer 4

List the properties of a Covalent Network
Melting and boiling point - VERY HIGH
State at room temperature - SOLID
Electrical conductivity - NEVER (except graphite)
Solubility in water - NO

Question 5

List the properties of a Covalent Molecule
Melting and boiling point?
State at room temperature?
Electrical conductivity?
Solubility in water?

Answer 5

List the properties of a Covalent Molecule
Melting and boiling point - LOW
State at room temperature - LIQUID, GAS AND SOLID
Electrical conductivity - NEVER (low conductivity in water)
Solubility in water - NO

Question 6

Explain the variations in melting points

Answer 6

When a substance melts, the forces of attraction that hold the substance together as a solid are broken
Covalent Molecules - WEAK BONDS
Covalent Network- STRONG
Ionic Lattice - STRONG

Question 7

Describe the variation in Electrical Conductivity

Answer 7

In order for a substance to conduct electricity it must have mobile charged particles such as electrons or ions
Covalent Substances - NEVER (except graphite)
Ionic Substances - ONLY AS LIQUIDS OR SOLUTIONS

Question 8

Give the definition of an electrolyte and explain the process of electrolysis

Answer 8

An electrolyte is a substance that allows electricity to flow through it. It is possible to show that ions move when electricity is passed through it by using COLOURED IONS.
Electrolysis is the breakdown of a compound using electricity.
Metals always form at the negative electrode!

Question 9

Explain the variation in solubility

Answer 9

When a solid dissolves the forces of attraction which hold the molecules together are broken
With solubility there are many exceptions to the general rules but
Covalent substances- NEVER conduct, low conductivity in water (of course excepting carbon graphite)
Ionic Substances- MOLTEN or SOLUTION

Question 10

Describe the process of solute to solution

Answer 10

Solute dissolved in solvent to create a solution. The solution becomes saturated when no more solute can be dissolved into the solution

Question 11

What is a metallic bond

Answer 11

Metals have a small number of outer electrons that are free to move. This leaves positively charged ions surrounded by negatively charged electrons. The attraction for the positive ion from the moving electrons holds the atoms together and forms a metallic bond. These bonds are very strong which is why metals are solid at room temperature

Question 12

What are the properties of an element

Answer 12

The properties of a substance depend on the types of bonds that hold the atoms together