The carbon atoms in saturated hydrocarbons are linked with single covalent bonds to their neighbors. The chains of saturated hydrocarbon are therefore well compact with hydrogen bonds between one another. This is why most saturated hydrocarbons are solid at room temperature. Unsaturated hydrocarbons have kinks in their chains that interrupt hydrogen bonds between chains. These kinks are because some carbon atoms in the chains have double or tripple covalent bonds.
