GCSE · Chemistry · AQA · Spec 8462

Giant covalent structures

Some solids are giant structures where strong covalent bonds link atom to atom throughout the structure.

What you need to know

Giant covalent substances are solids with very high melting points.
All atoms in a giant covalent structure are linked to other atoms by strong covalent bonds.
Melting or boiling requires strong covalent bonds in the structure to be overcome.
Diamond, graphite and silicon dioxide are examples, and giant covalent structures can be recognised from bonding-and-structure diagrams.

The big picture

Giant covalent substances are solids with very high melting points. All the atoms in their giant structures are linked to other atoms by strong covalent bonds. To melt or boil these substances, those strong covalent bonds must be overcome. Diamond, graphite and silicon dioxide are examples, and you should be able to recognise giant covalent structures from diagrams of their bonding and structure.

TONIGHT'S REVISION

Giant covalent structures

Strong covalent bonds throughout a giant structure explain why these solids have very high melting points.

Why the melting point is so high

Reason it through

Why do giant covalent substances have very high melting points?

Link 1 of 3

First link · your turn

What links the atoms throughout the giant structure?

Locked — reveal the link above first

Relationship matrix

Tap any cell to reveal it. Tap a column header to read one property down every item.

	Structure type	What links atoms	Melting behaviour
Diamondform of carbon
Graphiteform of carbon
Silicon dioxidesilica

Each cell hides a short answer and the reason behind it. Predict before you tap.

How to read a structure diagram

Follow the bonding before deciding what the diagram represents.

Which structure fits?

Commit to the structural clue before revealing the answer.

Which diagram description best supports identifying a substance as giant covalent?

Build the property explanation

Problem

Explain why a giant covalent substance is solid with a very high melting point.

Key points

1Giant covalent structures are solids.

2They have very high melting points.

3Strong covalent bonds link atoms throughout the structure.

4Those covalent bonds must be overcome to melt or boil the substance.

5Diamond, graphite and silicon dioxide are giant covalent structures.

Worked example

Problem

A diagram shows atoms joined to other atoms by covalent bonds throughout a giant structure. Explain why the substance has a very high melting point.

🧠

Memory hook

GIANT means bonds throughout: strong covalent bonds run through the structure, so melting needs those bonds overcome.

⚠ Watch out

Do not explain melting by saying weak forces between molecules are overcome; giant covalent structures require covalent bonds to be overcome.

✓

Check yourself

Why does a giant covalent substance have a very high melting point?

Flashcards

(6)

What state are giant covalent substances in?

They are solids.

What kind of melting points do giant covalent substances have?

They have very high melting points.

What links the atoms in a giant covalent structure?

Strong covalent bonds link the atoms to other atoms throughout the structure.

What must be overcome when a giant covalent substance melts or boils?

Strong covalent bonds in the structure must be overcome.

Name three examples of giant covalent structures.

Diamond, graphite and silicon dioxide.

How can you recognise a giant covalent structure from a diagram?

Look for atoms linked to other atoms by covalent bonds throughout a giant structure.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

Learn Giant covalent structures properly — interactive practice, marked questions and flashcards.

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