Some uncountable nouns have different meanings when they are used as

Some uncountable nouns have different meanings when they are used as countables.
What is the difference in meaning between the two uses of each noun?
1.There isn't enough room in my car.
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 can't repair the iron.
5.They've got much time.
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