an amount of~ / amounts of ~

Question

It is very confusing when using these expressions.

I saw the following sentence in my English textbook :

ex1)"Even small amounts of gases can have a large effect."

Being on a textbook means it's gramatically right, so I did not think anything about it. I just read and understood it. Just thought to myself "Oh, gas can be plural sometimes. I wonder when it would be?"

But suddenly. I encountered this:

ex2) "Even a small amount of gases can have large effects."

...Now I am beginning to get counfused...
Do they carry same idea? Not exactly, but similarly?

What is the difference between "an amount of ~" and "amounts of ~"?
And what verbform should be used accordingly? (is/are , flows/flow, for example)

We say "A cup of coffee is helpful.", but we don't say "A number of people is in the room."

What about 'amount'?
"A small amount of gases (have / has) a large effect"
Which is right?

I talked too much,
My questions are:

1.What is the difference between "an amount of ~" and "amounts of ~"?
?
2. Are the first two example sentences gramatically right?
3. "A small amount of gases (have / has) a large effect" -> Which is right?

...Somtimes I really don't want to think about grammar... T.T

Mister Micawber · Accepted Answer

VaCcine XOex1)"Even small amounts of gases can have a large effect.....Oh, gas can be plural sometimes.

No; it is 'amount' that is plural, not gas. (Although 'gas' can be plural: Oxygen and Nitrogen are gases.)

VaCcine XOex2) "Even a small amount of gases can have large effects." ...Do they carry same idea? Not exactly, but similarly?

Yes, the same idea, almost exactly.

VaCcine XOWhat is the difference between "an amount of ~" and "amounts of ~"?

Any one amount and any amounts

VaCcine XOWe say "A cup of coffee is helpful.", but we don't say "A number of people is in the room."

And we don't say 'amounts is'.

VaCcine XO"A small amount of gases (have / has) a large effect"Which is right?

A small amount has. Andsmall amounts have.

VaCcine XO..Somtimes I really don't want to think about grammar...

It would help us and yourself if you marshalled your thoughts before you post, not as you post. This is not a chat room.

Fivejedjon · Answer

VaCcine XOBeing in a textbook means it's grammatically right,

Not necessarily. There are some pretty poor books around.

VaCcine XO · Answer

Thank you very much, sir.

Mister MicawberIt would help us and yourself if you marshalled your thoughts before you post, not as you post. This is not a chat room.

I would like to apologize first, for making you unpleasant for my behavior. I was a bit rude. I didn't mean to disrespect anybody here though. I'm sorry.

English is a foreign language to me. And there's no one who speaks English as the mother tongue.
Even with very familiar expressions, once I feel something is not right, I cannot help thinking about grammar rules, and it is somewhat annoying sometimes.
That is why I come here and ask for help. So I thank you all the teachers here, and sorry again.

One thing I was confused about was this:
"A number of people are in the room." -> singular subject, plural verb
"An amount of gases has a large effect." -> singular subject, singular verb
(I know 'a number' is not a focus(subject) here. I'm trying to show why I was confused:structure)

They seem to have same structure.
But while in the first, the verb agrees with 'people', not 'a number',
in the second, the verb agrees with 'an amount', not 'gases'.

Of course, 'people' are in the room, not 'a number'.
Then, 'an amount' has a large effect, not 'gases'??

Am I missing something? What makes this difference? Why do we focus on 'people' in the first one, and on 'an amount' in the second? Maybe it's not about grammar but it's just an idiom?

I could not explain it to myself, and was getting confused.

Thank you.

VaCcine XO · Answer

Yes sir, I agree.
But as an English learner, I tend to trust textbooks (published by the government) first.

Mister Micawber · Answer

VaCcine XO I tend to trust textbooks (published by the government) first.

Trusting the government is always a risk.

Mister Micawber · Answer

VaCcine XO"A number of people are in the room." -> singular subject, plural verb

No. plural subject ('people'). 'A number of' is a phrasal quantifier.

VaCcine XOAn amount of gases has a large effect." -> singular subject, singular verb

Right. Subject is 'amount'.

VaCcine XO it's just an idiom?

Right: 'a number of' is an idiomatic phrase. Compare:

A number of people are here.
The number of people is small.

an amount of~ / amounts of ~

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