Chemistry is dis b or c #2select the atomic models that belong to the same element.

Srry if I'm late the answer to the first question about chemical changes is B. when a new substance is formed, it's going to be chemical. For example, when you burn paper, it turns into ash, which is a new substance. The burning is a chemical change. C is wrong because you can undo the mixture.

For number 2, the trick is to check if there is a carbon is double bonded to another carbon. Then it would be unsaturated. You can also check if there's a kink the chain. So therefore,

saturated is 3-methl..  and propane

unsaturated is propyne heptyne and cyclpentene

good luck!