It lowers the freezing point.
Yes
The antifreeze provides corrosion protection until the corrosion package is " used up " and it raises the boiling point and lowers the freezing point of the water
You dilute your antifreeze. If you buy prediluted 50/50 antifreeze, then you'll dilute it more than you're supposed to. If you buy straight 100% antifreeze, you're actually supposed to dilute it yourself by adding an equal amount of water to the antifreeze you put it. Your vehicle will be fine. Stop freaking out. Get a coolant flush.
Yes. Never add pure antifreeze. Pure antifreeze will actually freeze before a 50/50 mix. Add coolant that is a 50/50 mix of antifreeze and distilled water. You can buy it already pre-mixed.
My engine coolant is a 50 / 50 mix of antifreeze and distilled water so adding water will just dilute the mixture more and weaken the antifreeze so the coolant mixture will freeze at a warmer temperature and it will reduce the corrosion protection if there is not at least 40 % antifreeze
Enviromentally, not so good. And why would anyone consider do such?
Your engine should be cold ( to be on the safe side) when adding antifreeze/coolant. i let the car sit overnight and then add it.
Water can be used in an emergency but there is no corrosion protection like a mixture of antifreeze and preferably distilled water ( until the corrosion protection in the antifreeze is " worn out " ) Also , adding just straight water will dilute the antifreeze so the temperature at which the mixture freezes will not be as low
The dependent variable would be the freezing point of the solution.
( NO ) with the engine cool
Antifreeze should be a 50/50 mix with water. If you bought pure coolant, mix with water. If you bought premix (already 50/50) pour in straight.
Always use antifreeze. Water does not have any water pump lubricants or anti corrosion properties, antifreeze coolant does.