which of these don't complete have a complete sense? 

Water is a compound made up of hydrogen and oxygen, so pure water would be water that contains nothing but hydrogen and oxygen. However, pure water of this sort does not normally exist except in the controlled environment of a laboratory. Even in a laboratory pure water is hard to come by.If you want to know if your home's drinking water contains unsafe levels of lead, have your water tested. Testing is the only way to confirm if lead is present or absent. Some faucet and pitcher filters can remove lead from drinking water.A physical test for pure water is testing the boiling or freezing point. Pure water will boil at 100 degrees Celsius and freeze at 0 degrees Celsius. One chemical test is to use cobalt chloride paper - the paper will turn from blue to pink in the presence of water.A physical test for pure water is testing the boiling or freezing point. Pure water will boil at 100 degrees Celsius and freeze at 0 degrees Celsius. One chemical test is to use cobalt chloride paper - the paper will turn from blue to pink in the presence of water.Water is a compound made up of hydrogen and oxygen, so pure water would be water that contains nothing but hydrogen and oxygen. However, pure water of this sort does not normally exist except in the controlled environment of a laboratory. Even in a laboratory pure water is hard to come by.