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Year 10
AQA
Foundation

Properties of covalent substances

I can describe some different structures that non-metal atoms can form using covalent bonding and describe the properties of covalent compounds.

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New
New
Year 10
AQA
Foundation

Properties of covalent substances

I can describe some different structures that non-metal atoms can form using covalent bonding and describe the properties of covalent compounds.

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. Typical atomic radii, and bond length, are in the order of 10⁻¹⁰m.
  2. Non-metal elements and non-metal compounds form covalent structures.
  3. Simple covalent substances have no free moving charge carriers so cannot conduct electricity (some giant covalent can).
  4. Small molecules are usually gases or liquids with relatively low melting and boiling points.
  5. Giant covalent structures have high melting/boiling points because strong covalent bonds need to be broken.

Common misconception

Pupils often think that covalent bonds are broken when any covalent structure undergoes a change of state; not just those in giant covalent structures.

Use physical models to show the difference between a simple covalent structure and a giant covalent structure. Explain that it is the weak intermolecular forces that are overcome when a simple covalent molecule changes state.

Keywords

  • Molecule - a particle consisting of a fixed number of (two or more) non-metal atoms covalently bonded together

  • Covalent bond - the strong electrostatic force of attraction between a shared pair of electrons and the nuclei of bonded atoms

  • Intermolecular forces - the weak forces of attraction between molecules and molecular substances

  • Giant covalent structure - a substance that has a large regular arrangement of atoms all joined together by covalent bonds

  • Polymer - a long chain molecule formed by joining small molecules (monomers) together by covalent bonds

Show students a range of different covalent structures, alongside their molecular model to help them to make the links between substances, structures and properties. You could go on to test for electrical conductivity.
Teacher tip

Equipment

None required.

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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Starter quiz

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6 Questions

Q1.
What type of bond typically forms between two non-metal atoms?
Ionic bond
Correct answer: Covalent bond
Metallic bond
Q2.
How many pairs of electrons are shared between two carbon atoms in ethene (shown in the diagram)?
An image in a quiz
1
Correct answer: 2
3
4
8
Q3.
Which of the following is an example of a molecule formed by covalent bonding?
NaCl
MgO
Correct answer: CO₂
Fe
Q4.
How many electrons are shared in a single covalent bond?
Correct Answer: 2, two
Q5.
A displayed formula represents a covalent substance, showing to represent shared pairs of electrons between atoms.
Correct Answer: lines, sticks
Q6.
Arrange the following molecules by the number of covalent bonds each has, from least to most:
1 - H₂
2 - O₂
3 - N₂
4 - CH₄

Exit quiz

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6 Questions

Q1.
What is the typical size of atomic radii and bond lengths?
10⁻⁶ m
10⁻⁸ m
Correct answer: 10⁻¹⁰ m
10⁻¹ ²m
Q2.
Why can't simple covalent substances conduct electricity?
They have no atoms.
Correct answer: They have no free moving electrons.
They have no electrons.
They are too small.
Correct answer: They have no free moving ions.
Q3.
Giant covalent structures have high melting and boiling points because strong need to be broken, which requires a lot of energy.
Correct Answer: covalent bonds, covalent bonding
Q4.
What are intermolecular forces?
Strong forces between atoms.
Correct answer: Forces of attraction between molecules.
Forces that hold nuclei together.
Forces that repel electrons.
Q5.
Which of the following are true of polymers?
Correct answer: Most polymers exist in the arrangement of the solid state at room temperature.
Some polymers are made up of smaller molecules called monomers.
Correct answer: They have a simple covalent structure (molecules).
They conduct electricity well.
Correct answer: They are held together by covalent bonds.
Q6.
What happens during a change of state in simple covalent substances?
Covalent bonds are broken.
Correct answer: Intermolecular forces are overcome.
Atoms are rearranged.
Correct answer: Molecules move farther apart.