Is there 1000 kilograms in a liter?

Answer 1

No. A kilogram is a measure of mass while a litre is a measure of volume. The two measure different things and, according to basic laws of dimensional analysis, conversion between the two is not valid.

Some people still believe that there is a valid conversion in relation to pure water but that is only approximately true. Until 1964 (almost 50 year ago!) a litre was defined as the volume of one kilogram of pure water at 4 degrees Celsius and at a pressure of 760 millilitres of Mercury. That is one thousandth of the value mentioned in the question. With that definition a conversion would have been valid - but only for pure water and only under those conditions. In any case that definition of a litre was abandoned in favour of 1 litre =1000 cubic centimetres.

In fact the density of pure water, at 4 deg C and 760 ml of mercury is 999.9720 kg/metre3