6.2 Physical State and Melting Points

Introduction

Salts are ionic compounds, and their physical properties are very different from those of covalent compounds. At room temperature, salts are usually solids with high melting points. They form lattice structures and conduct electricity only when molten or dissolved in water.

This section explains the physical state, melting points, lattice structure, electrical conductivity, hardness, and brittleness of salts.

Definition

Physical State of Salts: At Standard Temperature and Pressure (STP), salts are usually solids due to the strong electrostatic forces of attraction between the oppositely charged ions, which form a tightly bound lattice structure.

In simple words: Salts are solid at room temperature because their ions are strongly held together in a lattice.

Main Idea

• At STP, salts are usually solids.
• This is due to the strong electrostatic forces of attraction between oppositely charged ions.
• These forces form a tightly bound lattice structure.
• These forces require significant energy to overcome, resulting in high melting points.
• Salts conduct electricity only when molten or dissolved in water.
• Salts are hard but brittle.

Core Concept

Key point: The strong electrostatic forces in the lattice explain the high melting points, hardness, and brittleness of salts.