Some / any / a lot of

Quantifiers

1. Some, any, a lot of

Some, any and a lot of are quantifiers, that is, they tell us that there is a certain number or quantity of something when we don't know or we don't want to say the exact number or amount.
A lot of
IMG UNIT 15-1
There is a lot of food!
Some
IMG UNIT 15-2
I have some questions.
Any
IMG UNIT 15-3
I haven't got any money.
They are usually placed before the noun they accompany.

2. When do we use some?

We use some in affirmative sentences when we want to express a certain number or amount of something. It is also used in interrogative sentences when they are offers or requests and the expected answer is a yes.
  Countable (plural) Uncountable
AFFIRMATIVE A certain number I've got some new glasses. A certain amount I have some money.
INTERROGATIVE A certain number Can I take some biscuits? A certain amount Can I have some milk?
IMG 15-04
Buy some beans, please.
IMG 15-05
Would you like some magazines to read?
Some is not used in negative sentences 

3. When do we use any?

In negative sentences, any is used to express that there is no amount or number of something. In interrogative sentences, it is used to ask about a certain number or amount of something.
  Countable (plural) Uncountable
NEGATIVE No number I haven't got any clean socks.
No amount There isn't any homework.
INTERROGATIVE A certain number Have you got any sisters?
A cetain amount Is there any sugar?
IMG 15-06
I haven't got any bread.
IMG 15-07
Are there any banks near here?

Any is not used in affirmative sentences or with singular countable nouns.

I've got some sweets. /  I've got any sweets.
There aren't any seats. /  There isn't any seat.

4. When do we use a lot of?

A lot of is used to express a large number or amount of something. It is used both with uncountable and plural countable nouns.
IMG 15-08
There are a lot of trees in this park.
IMG 15-09
Hurry up! We haven't got a lot of time.
A lot of is mostly used in affirmative sentences, although it can also be used in negative and interrogative sentences.

Remember!

  Use Examples
SOME A certain number or amount

Affirmative sentences

Offers and Requests

There are some pencils on the floor.

This box is too heavy. Do you need some help?

ANY

No number or amount

A certain number or amount

Negative sentences

Interrogative sentences

There isn't any homework.

Are there any vacancies?

A LOT OF

A large number or amount

Mostly in affirmative sentences

We need a lot of apples to make this cake.