Why is water (H2O) a liquid at room temperature while carbon dioxide (CO2) is a gas? What’s different about their structures that results in very different properties?

Question

Why is water (H₂O) a liquid at room temperature while carbon dioxide (CO₂) is a gas? What’s different about their structures that results in very different properties?

Answer 1

If you draw the Lewis dot structures for the two compounds, you'll see that water (H₂O) is bent and polar whereas carbon dioxide is linear and not polar. Water has relatively strong hydrogen bonds holding the molecules together but CO₂ has only dispersion forces acting as intermolecular forces. The weaker intermolecular forces explains why CO₂ is a gas whereas H₂O is a liquid at room temperature.