Chemistry · Properties & uses

Structure & Properties.

Why does ice melt in your hand while salt needs a furnace? Why does copper carry a current but sugar never does? It all comes down to what the particles are, and how strongly they hold on to each other.

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Key words

Melting pointThe temperature at which a solid turns to a liquid. The stronger the attractions between the particles, the higher it is

Molecular substanceMade of separate molecules: strong covalent bonds inside each molecule, only weak attractions between molecules. Low melting point, doesn't conduct. Example: water

Ionic solidA 3-D lattice of positive and negative ions. High melting point, brittle, conducts only when molten or dissolved. Example: salt

Metallic solidPositive metal ions in a sea of delocalised electrons. Conducts as a solid and when molten. Example: copper

Covalent network solidAtoms joined by covalent bonds in a giant network. Very high melting point. Examples: diamond, silica (3-D); graphite (2-D layers)

Conducting electricityNeeds charged particles that are free to move: delocalised electrons, or ions in a liquid or solution

Where this comes from: the particles themselves are in Inside an Atom; the electron sea is in Inside a Metal; ionic compounds are in the Precipitate Lab.

Narration voice: Max, generated with ElevenLabs.