Here's why:

* Hydrocarbons: Decane is a hydrocarbon, meaning it's made up of only hydrogen and carbon atoms.

* Chain Length: Decane has a relatively long carbon chain (10 carbon atoms).

* Intermolecular Forces: The primary intermolecular forces in decane are weak London dispersion forces. While these forces increase with the length of the carbon chain, they're not strong enough to overcome the kinetic energy of the molecules at room temperature.

Therefore, the molecules in decane have enough energy to move around freely, making it a liquid.