1) In the first sentence room has a meaning of space and in the second amount of rooms.
2) In the firs sent. wood is log (полено). In the second sent. is forest.
3) In the first sentence hair is her hair cut and in the second hair is one hair
4) In the first iron is the material, in the second iron is an ironing appliance (прибор для глажки)
5) In the first sent. time is unit of measurement (единица измерения), in the second sent. time is a frequency(частота)