A homologous row of alkanes, i.e. saturated hydrocarbons of general formula CnH2n+2 is presented in the model. One can see that each consequent member of the row is produced by substitution of one hydrogen atom of the initial compound by group CH3. As a result, a molecule of alkane either can be a long chain molecule (shown in this model) or more complicated branched structure may be produced (shown in the model "Isomers"). The model demonstrates as well that even in the case of linear structure (carbon atoms are in a row) the carbon atoms are not situated in a straight line. This happens due to tetrahedral orientation of the four identical bonds in alkanes which, in turn, is formed as a result of sp3 hybridization of carbon orbitals. Moreover, the real structure of alkanes is even more variable due to free rotation around the sigma bonds that links carbon atoms in alkans. Therefore, the relatively long molecules of alkanes may seldom spread into the whole length. The model is operated by the "Next" and the "Reset" buttons. Clicking on the "Next" button will induce a substitution of one of the hydrogen atom by CH3 group. As a result, the molecule is converted into the next member of the homological row. The "Reset" button returns the model into initial state.