Solids, liquids, and gases

1. Phases of Matter

Organic compounds can exist in solid, liquid, or gaseous states, depending on their intermolecular forces and molecular size.

2. Properties of Solids, Liquids, and Gases

Solids	Liquids	Gases
Strong intermolecular forces.	Weaker intermolecular forces.	Very weak intermolecular forces.
Definite shape.	Takes the shape of its container.	Expands to fill its container.
Larger alkanes ($C₁₇$ and bigger) are waxy solids at STP.	Alkanes from $C₅ – C₁₆$ are liquids at STP.	Small alkanes $(C₁ – C₄)$ are gases at STP.
Larger alkenes ($C₅$ and bigger) are solids at STP.	Alkenes from $C₅ – C₁₂$ are liquids at STP.	Small alkenes $(C₂ – C₄)$ are gases at STP.
Haloalkanes are mostly solids or liquids at STP.		A few haloalkanes are gases at STP.

3. Factors Affecting the State of Organic Compounds

• Bigger molecules (e.g. alcohols, ketones, esters, carboxylic acids) tend to be solids due to strong intermolecular forces.
• Smaller molecules (e.g. aldehydes, ketones, esters) are often liquids at STP due to weaker intermolecular forces.

Key Takeaways

• Stronger intermolecular forces = Solid state.
• Weaker intermolecular forces = Liquid state.
• Very weak intermolecular forces = Gas state.
• The size of the molecule and the type of intermolecular forces determine whether a compound is a solid, liquid, or gas at standard temperature and pressure (STP).