Some uncountable nouns have different meanings when they are used as

Some uncountable nouns have different meanings when they are used as countadles.
What is the difference in meaning between the two uses of each noun.
1.There isn't enough room in my.
There are eight rooms in the house
2.We put some wood on the fire
We used to go for a walk in the woods
3.My sister has dark hair
I found a hair in my soup
4.The bridge was мейд of iron
I cant repair the iron
5.Theyve got much time
We have English lessons two times a day