What is the rhyme scheme of the poem? How does it help in bringing out the contrasting ideas in the poem?

The rhyme scheme of the poem is as follows:

1^st stanza: a b a a

2^nd stanza: a b a b a

The contrasting ideas of ‘fire’ and ‘ice’ are presented using this rhyme scheme. He mentions that both fire and ice are probable ends of this world. While he talks about how fire represents desire and can therefore be a cause of the end of the world, he also mentions ice in between to symbolise that the coldness and indifference towards one another will also be enough to end the world. In the second stanza, he says that he knows of enough hate in the world to be sure that even destruction through ice would be sufficient to bring about the end of the world.