(Un)countable Facts

How do you distinguish uncountable nouns from countable ones? Basically, the uncountable ones are those things that cannot be quantified, or at least very dificult to quantify.

All liquids, such as milk, soda or gasoline, cannot be counted, unless there are found in containers, such as a glass, a bottle or a tank. For example: 

3 glasses of milk / 2 bottles of soda / 1 tank of gas

There are other things that are difficult to count, like rice, spaghetti or flour. You could count each grain [1] of rice or each strand[2] of spaghetti, but what a pain[3]! Don't bother[4]! To count them, containers or measurements canbe used. For example: 

1 bag of flour / ½ cup of flour

Later, there are very general things that cannot be counted, but whose subgroups can. For example, you can't count money but you can count euros, pounds or dollars. Or you cannot count fruit but you can count apples, oranges or bananas.

some money / four dollars

some fruit / four bananas

Then there are some things that are countable when you talk about them as a whole[5], but uncountable when you talk about a part of them. For example:  

2 pieces of chicken / 3 chickens

2 slices of cake / 3 birthday cakes

So now you have the facts about countable and uncountable nouns. Whoever said you can't have your cake and eat it too[6]!

[1] grano, [2] hilo

[3] ¡que rollo!

[4] ¡No te molestas! [5] entero

[6] no puedes estar en misa y repicando