I've stumbled upon few photographs that capture water in all three phases - solid, liquid and gas (well, vapor). And then I thought to myself, there is probably a good reason why life works with water that is such (having high boiling and freezing points). If water had a lower boiling point, we'd dry out; if it were any higher, we couldn't cool off (this was just the first thing to come to my mind). Then I tried to find a reason why water was crystallizing at such a temperature, but nothing was coming to me. If anything, ice is an annoyance to nature forcing it to find ways around it. It is handy that ice is less dense than water, so lakes don't freeze, but it would be even better if water was not freezing at all. What would happen if water did not freeze at 0°C, but at a considerably lower temperature?
closed as too broad by kingledion, L.Dutch♦, Aify, StephenG, HDE 226868♦ Jan 13 '18 at 23:04
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The polar ice caps would be much smaller, if they existed at all. The consequence is that one of the primary cooling processes for the planet (wind coming off the caps and northern latitudes) would not cool the planet as it does. Your ocean levels would change, deserts would be larger and there would be more of them.
The water cycle would also change as there would be less water for run-off during spring thaws. You could still fill resevoirs, but their fill patterns would change drastically.
But the worst things of all: no ice-cold drinks or ice cream.
Because your body wouldn't be capable of withstanding the temperatures required for ice.
Snowpacks wouldn't form. So in the spring, there would be no source of water to swell the river size. This would make rivers more static and would make it more likely that they would dry out in hot, dry weather in summer.
On the Earth, there would be less water trapped as ice at the poles or in glaciers, so the sea level would be higher and there would be less land (Coloradans might take daytrips to the beach...in Kansas). The oceans would also be less salty. The Salt Lake might not be so salty. The Dead Sea might not be dead. No glaciers might mean no fjords (Slartibartfast would be sad).
Water would have less ability to crack things. Now, water seeps into places, freezes, and cracks open the larger rock. So weathering would be less effective. There would be more big rocks and fewer small stones.
Note that a small change, perhaps a degree or two, would be unlikely to have much effect. But that's also true of changing the boiling point. I'm assuming a large change, say to -40 degrees (same in both scales). That's a rare temperature in most places, so most places would never see frozen water. And even fewer places would see frozen water year round.
Ice ages would be brisk ages or something, making them more survivable. People, animals, and plants would not experience frostbite until the lower freezing temperature. They might still experience hypothermia. The Earth might still have dinosaurs, as they might better survive the cold periods.
State of the art
Water is a quite unique chemical compound. It behaves the way it does (and not the way its neighbours H2S and H3N (those stinky gases) behave) because of (!) inter-molecular bindings. Basically, those water molecules don't behave like single molecules, they connect to a larger structure.
This fact explains the well-known (even in advanced high school chemistry, where I picked it up) issue of "water paradox". Water does not freeze and boil at the temperature you would expect from something hydrogen.
(!): Hydrogen flouride (HF, that thing that eats through glass) also exibits inter-molecular bindings, though.
The effects of a change
So what happens if water does not have inter-molecular bindings to the extent in has in our world?
- No water oceans
- No water vapour (that can condense), but a lot stinky gas
- Nothing known from any biology books functions like it should, actually, not around anymore.
That's pretty bad, if we change the properties of water. What about using something different, such as hydrogen flouride?
Not water-based life
We basically build up all life and physical traits out of, say, HF, and not water (@). For ones, HF is a badass acid. Much worse than water. So, oceans of HF would probably be much more errr... caustic to the shores and seabed. Same for erosion from hydrogen flouride rains.
(Funnily, HF is regarded as a quite weak acid, but it depends in dilution with water. In a proper mix it even eats through glass.)
It seems (I have no degree in chemistry of biology to offer more in-depth knowledge) that HF-based life would be theoretically possible. A lot of fine-grain biological workings relies on a similar sort of hydrogen bounds water has. But since HF has it too, life would be probably Ok.
It's a cold life, actually. HF boils at 19.5 °C (what is 100 °C for water) and freezes at −83.6 °C (0 °C for water). It's a bit less dense than water, but almost the same in the liquid form.
The funny part is that HF is miscible with water. So you'd have some kind of "ice dragons". Creatures that live at somewhat -50 °C, whose breath (containing vapour of HF analogously with water-based animals) forms with atmospheric water a strong acid.
So, even if they would breathe oxygen and have elsewise compatible requirements towards habitability, they'd need to live in a freezer and don't you let them sneeze on you.
(@): It's a classic game of old Sci-Fi, folks wrote and dreamed about silicon-based life – NOT in sense of computers and cyberworld, but about life based on Si and not on C.