“Liquid water”?

Where are you seeing this prevalence of use? I've only seen people use "liquid water" when they are clarifying that the water's state it is not solid or vapor. You might not believe the clarification is necessary, but others might so the speaker (or author) employs its usage.

To answer your two questions, no and no.

Have seen it used in a number of reports, latest of which was an article in The Independent.
IMHO to the man in the street the terms ice, water, steam, all refer to H20 in its various forms and that differentiation would only be required for any exceptions to that such as "dry ice", "frozen CO2","methane gas", etc etc.

@Hairy Scot - unfortunately you don't say what the Independent article was about, but all the recent instances of liquid water I've found in the newspaper refer to cosmology, apart from one which is about the Antarctic. The most recent, from 11 October is in an article about a newly discovered planet with "surface temperatures reaching a blistering 2,150C with no possibility of liquid water and therefore life." - I think for cosmologists and geologists the state of that water is very important in terms of supporting life. I think what you've stumbled across is simply a scientific term, used especially amongst cosmologists and perhaps geologists, and nothing to get worried about.

If I can give an analogy - to the general public 'Classical music' means a type of composed 'serious' music written any time between the 17th century (or even earlier) and today. But to musicians themselves, Classical Music is a much more specific term, referring to a particular style of music composed between about 1750 and 1820.

Just as until I started reading language websites I thought redundancy more or less only related to people being laid off work. The way you use it is very specific and probably not known to the general public, (in Britain at least; I think this is rather an American preoccupation). It doesn't even appear in the index of Michael Swan's Practical English Usage, the bible for any TEFL teachers. But on this forum you're speaking to a relatively specialist audience (some of whom seem to think this is a very important issue) and you use it in a way you assume they'll understand.

What I'm trying to say here is that specialists often use words in different ways to the general public, and as you originally said, you have seen this mainly in science reports, and I would hazard a guess, mainly to do with cosmology. I'd be interested if you can give us any examples of the term 'liquid water' being used outside articles on cosmology or geology.

http://www.independent.co.uk/search/simple.do?destinationSectionUniqueName=search&publicationName=ind&sortString=publishdate&sortOrder=desc§ionId=506&articleTypes=news&pageNumber=1&pageLength=10&startDay=1&startMonth=1&startYear=2010&useSectionFilter=true&useHideArticle=true&searchString=%22liquid+water%22

That should be - for 'many TEFL teachers', not 'any'.

@Warsaw Will
Article was indeed related to cosmology, and while I do take your point on the topic, something about the phrase does strike me being odd.
But then maybe that's just me.

:-))

That should be "as being odd"

I've heard news reporters refer to tornadoes as "storm funnels". I didn't realize that "tornado" was somehow a pejorative or culturally insensitive term. "Avalanche", "mudslide", and "sink hole" must be really offensive to the environmentally aware. Let's all work together to stop water, wind, and rock related ignorance!

Depending on the context 'water' can be used to describe the liquid state of a collection of H2O molecules, any collection of H2O molecules or even a single H2O molecule (in which case trying to describe it as being solid, liquid, gas, etc. without consideration of the other matter around it is essentially meaningless).

So, while it may sound strange it is indeed correct when using the following definition of the word: "a collection of H2O molecules." Because, of course, a collection of water molecules, depending on their temperature and pressure, could be in one (or perhaps more) of several different states.

In my geography homework they ask if snow and ice are examples of liquid water but i can't find it in the book and i can't find a good awnser online can you help me?

Your observation is very correct. That is a question which I have been looking answer for.

It is not only cosmology, please check articles on Planetary science, Crystallography, Geophysics, Glaciology, Permafrost, Ice crystals in soil etc. everywhere they use the term liquid water. Probably it is in order to differentaite the state of water but it is not required as water is actually liquid, else we refer it as crystal, ice, snow or vapour. Thanks for asking this question and to all others please read before answering. Just google it or preferably search it on researchgate or google scholar..best wishes

Modeling of Coupled Water and Heat Transfer in
Freezing and Thawing Soils, Inner Mongolia

One article for your reference. I am having atleast 100 other examples. Best Wishes

'Water' does not, by definition, mean water in its liquid state; it also applies to its solid state (ice) and its gaseous state (steam). There is absolutely nothing wrong with the term, 'liquid water', The term is used when it's necessary to distinguish water in its liquid state from its solid or gaseous states. In the case of Mars, we know that there are large areas of ice but to discover water in its liquid state is something else.

Watching Brian Cox repeatedly use “Liquid Water” in BBC’s Universe brought me here.
Is this not a tautology?