Boiling points of the alkanes

The boiling points of the first eight alkanes are listed in kelvin. You will pick out the ones that are gases in a room, find how much each step along the series raises the boiling point, and find the first liquid. Then the program draws both.

The idea. An alkane is a gas in a room if it boils below the room's temperature. Each step adds a $\text{CH}_2$, and the forces between the molecules grow.

Your tasks.

1. In gases, return the carbon numbers of the alkanes that boil below room.
2. Fill steps with the rise in boiling point from each alkane to the next.
3. Find first_liquid, the carbon number of the first alkane that is a liquid at $298\ \text{K}$.