Identifying a tree help
Realistically it is not easy to identify a tree from just a leaf. It is helpful to know the size, whether the leaves are arranged in an opposite or alternate manner, when they come out, does the tree flower, what color are the leaves in the fall, etc. To get a positive ID, it would be helpful to bring a branch to your local plant nursery. Possibly it could be some kind of poplar - maybe a quaking aspen. But if you positively need to know, I would bring it somewhere for a positive ID.