Home

The UK’s Leading Online Chemistry Learning Platform, Taking Students Directly to the Very Best Resources
Home » GCSE Revision Lessons » AQA GCSE Chemistry (8462) Section 4.2 Revision of Bonding, Structure and the Properties of Matter Topic:

AQA GCSE Chemistry (8462) Section 4.2 Revision of Bonding, Structure and the Properties of Matter Topic:

Section 4.2 Revision of Bonding, Structure and the Properties of Matter Topic:

(Why? What? How?)

Specification Link: Pages 25 – 33      http://filestore.aqa.org.uk/resources/chemistry/specifications/AQA-8462-SP-2016.PDF

There are three types of strong chemical bonds: ionic, covalent and metallic.

 

IONIC BONDING: Strong electrostatic attractions between oppositely charged ions.

Why does it happen?

What is it?

For ionic bonding the particles are oppositely charged ions. Ionic bonding occurs in compounds formed from metals combined

with non-metals. (G1,2,6,7)

How does this affect the properties of ionic compounds?

Ionic compounds have regular structures (giant ionic lattices) in which there are strong electrostatic forces of attraction in all directions

between oppositely charged ions.

These compounds have high melting points and high boiling points because of the large amounts of energy needed to break the many

strong bonds.

When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow.

Knowledge of the structures of specific ionic compounds other than sodium chloride is not required.

 

Watch and learn, YouTube links:

 

COVALENT BONDING: Small molecules/macromolecules/polymers

 

Small Molecules

Why does it happen?

What are small molecules?

For covalent bonding the particles are atoms which share pairs of electrons.

Covalent bonding occurs in most non-metallic elements and in compounds of non-metals.

Dot and cross/limitations/shape.

How does this affect the properties of small covalent molecules:

Substances that consist of small molecules are usually gases or liquids that have relatively low melting points and boiling points.

These substances have only weak forces between the molecules

(intermolecular forces).

It is these intermolecular forces that are overcome, not the covalent bonds, when the substance melts or boils.

The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points. (S & CH Why?)

These substances do not conduct electricity because the molecules do not have an overall electric charge.

Students should be able to use the idea that intermolecular forces are Weak.

 

Macromolecules:

Why do they form?

What are macromolecules?

            How does this method of bonding determine the properties of macromolecules?

 

Substances that consist of giant covalent structures are solids with very high melting points.

All of the atoms in these structures are linked to other atoms by strong covalent bonds.

These bonds must be overcome to melt or boil these substances.

Diamond and graphite (forms (allotropes) of carbon) and silicon dioxide (silica) are examples of giant covalent structures.

 

Students should be able to recognize giant covalent structures from diagrams showing their bonding and structure.

 

Polymers:

A combination of many strong covalent molecules and intermolecular forces make very large molecules known as polymers: What do we need to know?

  • Polymers have very large molecules.
  • The atoms in the polymer molecules are linked to other atoms by strong covalent bonds.
  • The intermolecular forces between polymer molecules are relatively strong

and so these substances are solids at room temperature.

Students should be able to recognize polymers from diagrams showing their bonding and structure:

 

Watch and learn, YouTube links:

 

METALLIC BONDING: Atoms with shared delocalised electrons

 

Why does metallic bonding form?

What is Metallic Bonding?

For metallic bonding the particles are atoms which share delocalised electrons.

Metallic bonding occurs in metallic elements and alloys.

The electrons in the outer shell of metal atoms are delocalised and so are free to move through the whole structure.

The sharing of delocalised electrons gives rise to strong metallic bonds.

How does this type of bonding determine the properties of metals?

Metals have giant structures of atoms with strong metallic bonding.

This means that most metals have:

  • High melting and boiling points.
  • In pure metals, atoms are arranged in layers, which allows metals to
    • be bent and shaped.
  • Metals are good conductors of electricity because the delocalised
    • electrons in the metal carry electrical charge through the metal.
  • Metals are good conductors of thermal energy because energy is transferred
    • by the delocalised electrons.

 

A problem with metallic bonding:

Pure metals are too soft for many uses and so are mixed with other metals to make alloys which are harder.

Students should be able to explain why alloys are harder than pure metals in terms of distortion of the layers of atoms in the structure of a pure metal.

 

Watch and learn, YouTube links:

 

Chemical language relating to substances including state symbols:

  1. Know your ions
  2. If you are unsure of these know how to use the Periodic Table to work out the valency of an element
  3. Know your solubility rules; here is a useful overview:
  • All nitrates are soluble
  • All chlorides are soluble except for silver, mercury and lead
  • All sulfates are soluble except for calcium, strontium, barium and lead
  • All carbonates are insoluble except for sodium, potassium and ammonium
  • All hydroxides are insoluble except for sodium, potassium and ammonium
  1. State symbols:
  • s             solid
  • aq          aqueous
  • l              liquid
  • g            gas

How do these apply to the solubility rules?

 

Examination Question Links:

http://filestore.aqa.org.uk/resources/chemistry/AQA-84621H-SQP.PDF

https://images.scholastic.co.uk/assets/a/07/fe/topic2bondingstructureandthepropertiesofmatter-sp-1601833.pdf

 

There are no products to list in this category.
Continue