Classroom Secrets: The Properties of Ionic Compounds

Get your students top marks on the properties of ionic compounds (Edexcel IGCSE Chemistry)

Teaching the properties of ionic compounds is a staple of the Edexcel IGCSE Chemistry course, and for good reason. It underpins several other key topics, including electrolysis and bonding making it one of those foundational concepts that students need to understand rather than simply memorise.

I’ve seen it too many times over the years. Teachers delivering bulky PowerPoint presentations and telling students to “copy this down….” or “just learn this….’ Students will score higher marks in the exams if they can really understand that everything simply links back to the lattice structure.

Properties of Ionic Compounds #1

Start With the Big Idea: Structure Determines Properties

Students need to understand that all ionic properties come from one thing:

A giant ionic lattice made of oppositely charged ions held together by strong electrostatic forces.

Teacher tips:

Don’t teach the properties as isolated facts.

Instead constantly return to the same model.

Every time you introduce a property ask:

“What is happening inside the lattice?”

Key questions

1. What particles make up an ionic compound?
2. How are the ions arranged?
3. What holds the ions together?
4. Why are these forces so strong?

Properties of Ionic Compounds #2:

Teaching the Three core Properties

This is what your students need to understand to be able to score top marks about the properties of ionic compounds:

1. High Melting and Boiling Points
2. Electrical Conductivity When Molten or Dissolved in Water
3. Do Not Conduct When Solid

Common Misconceptions

Here are several activities that work great for demonstrating the theories that you are explaining in class. This topic can become a bit dry as it’s so theory based, but I’ve also included a few practical opportunities.

Practical Hooks

1. Show the students salt, sugar and wax. Ask them which would melt first? Students are often surprised that salt has such a high melting point.
2. Use the light microscopes to look at a few grains of salt. Students can draw what they see.

Demonstration

Use conductivity equipment with:

• Solid sodium chloride
• Molten Ionic compound (show a video if tricky to do).
• Salt solution

Properties of Ionic Compounds #3:

3. Link Every Property Back to Structure

This could be a useful table for your students, you could base your starters over a sequence of lessons on this table by pulling questions from it. Check out my blog on how to start you lesson right for a free downloadable starter you can edit for each of your lessons.

Properties of Ionic Compounds #4:

Hot Topic Questions

Rather than telling students to copy points, repeatedly ask these questions throughout your lessons. Repetition and consolidation are your best friend for this topic.

1. What particles are present in an ionic compound?
2. Can the particles move?
3. What force is acting between the particles?
4. What needs to happen before electricity can flow?
5. What happens when an ionic compound is heated?
6. Which property can you explain using the lattice model?
7. Is this describing structure or property?
8. Could this property be explained without mentioning the lattice?

These questions encourage deeper thinking and help students connect ideas rather than memorise isolated facts.

Properties of Ionic Compounds #5:

More common student misconceptions and how to address them

This will really test your students understanding on the properties of ionic compounds.

Misconception	Teacher Response
Ionic compounds contain molecules.	Reinforce that they form giant ionic lattices made of ions.
Electrons carry the current in ionic compounds.	Clarify that mobile ions carry the current.
Water itself conducts electricity.	Explain that dissolved ions are responsible for conduction.
Ionic bonds break during melting.	Emphasise that melting weakens enough electrostatic attractions for ions to move, but the substance remains ionic.
All solids conduct electricity.	Compare ionic compounds with metals and covalent substances to highlight the role of mobile charged particles.
Strong bonds mean a substance cannot melt.	Explain that strong electrostatic attractions require more energy to overcome, leading to high melting points rather than making melting impossible.

Properties of Ionic Compounds #6:

Retrieval Questions for Plenaries or Starters

1. What is a giant ionic lattice?
2. What holds the ions together?
3. Why do ionic compounds have high melting points?
4. Why can’t ions move in a solid?
5. Why do molten ionic compounds conduct electricity?
6. Why do aqueous ionic compounds conduct electricity?
7. Why are ionic compounds brittle?
8. Which particles carry the electrical current?
9. What must be true for electricity to flow?
10. Explain one property of ionic compounds using the words ions, lattice, and electrostatic attraction.

Properties of Ionic Compounds #7:

Exam Tips for Edexcel IGCSE

Students often lose marks because they write answers that are too vague. Encourage them to include precise scientific vocabulary. For example:

• Mention strong electrostatic attractions rather than simply “strong bonds.”
• Refer to a giant ionic lattice rather than just “a structure.”
• State that ions are free to move when explaining electrical conductivity.
• Distinguish between solid, molten, and aqueous ionic compounds, as conductivity depends on the state.

Practising full explanations, rather than one-word answers, will help students secure the higher-mark questions.

Conclusion

Remember, the goal is not for students to memorise five separate properties, but to recognise that every property can be explained by the same underlying models: the giant ionic lattice and the behaviour of its ions. When students are able to answer, “What is happening inside the lattice?”, they develop a deeper understanding that transfers well to exam questions.