Name an isomer of pentane (that is not cyclic) and write down its structure.
n-pentane is just the straight chain.
C-C-C-C-C with all the H atoms attached. Numbering the C atoms from the left as 1,2,3,4,5, just move C1 with its 3 H atoms (meaning the CH3 group) to C3 so that it is now
C-C(CH3)-C-C
We can't draw structures on the board but it would be named 2-methylbutane