Learn English – Two uncountable noun connected by “and”

Lightning and thunder are both uncountable nouns, but there are two of them, i.e. it is possible to count uncountable-noun words. For this reason we use the plural form are:

Lightning and thunder are both natural phenomena.

The confusion arises because we also have an idiomatic phrase in English thunder and lightning, which is treated as a (singular) noun phrase:

There is thunder and lightning in the sky.

The thunder and lightning is pretty scary, huh?

Technically you could break the noun-phrase from the singular "thunder and lightning" back into its constitutent parts of "thunder" and "lightning" and so something like this is technically grammatical:

(X) The thunder and lightning are pretty scary.

It is grammatical (replace the nouns to see this fact: "the rain and hail are pretty scary!" is perfectly grammatical), but it is extremely unidiomatic, and no native English speaker would say it.

First, times is a plural noun in your sentence. And two times indicates two of this same noun. You can't use an adverb in the blank below:

There is/are two _____ as much/many in this glass as in the other one.

This is verified by the Oxford English Dictionary:

time (noun)

19. In plural Preceded by a number

a. Expressing comparison:

followed by an adjective or adverb in the comparative degree (e.g. ten times bigger, ten times more slowly, ten times less), or by as or (now rare) so with an adverb of quantity (e.g. ten times as (or so) many (as), ten times as (or so) much (as)).

Notice we can say either

two times as much ______ as

or

two times as many ______ as

depending upon whether the noun in the blank is a mass noun or count noun. We use much with mass nouns and many with count nouns.

It is precisely because water here is being used as a mass noun that we use is:

In this glass, there is two times as much water as in that glass.

Take away the comparison terms and you are left with

In this glass there is water.

Now if we are comparing a count noun, we can use are:

In this glass there are two times as many ice cubes as in that glass.

And this is an expanded version of

In this glass there are ice cubes.

So far, so good. But now comes a big caveat. Many native speakers will use there's in this case also, either because they are considering the ice cubes as a single set or because there's is a frozen form that is used by native speakers even if the following noun is plural.

In this glass there's two times as many ice cubes as in that glass.

Many native speakers will even use there's for the reduced sentence

In this glass there's ice cubes.

Some native speakers will find that clumsy, terrible sounding and downright ungrammatical. But the point remains that there's is used by native speakers to refer to more than one of something. See Can we use "there is" for plural nouns? (especially the accepted answer).

So, for the above reason, you can say either

There are two liters of water.

or

There's two liters of water.

But you probably should use are in writing and formal spoken English.