/6 Science Quiz (for 12 to 16 years old): Quiz 18 1 / 6The hardest substance available on earth is Platinum Iron Gold Diamond 2 / 6Permanent hardness of water may be removed by the addition of sodium carbonate potassium permanganate alum lime 3 / 6Soda water contains nitrous acid carbon dioxide carbonic acid sulphuric acid 4 / 6Which of the gas is not known as greenhouse gas? Hydrogen Nitrous oxide Carbon dioxide Methane 5 / 6Bromine is a colourless gas black solid red liquid highly inflammable gas 6 / 6Potassium nitrate is used in glass salt fertiliser medicine Your score is 0% Restart quiz Next quiz Please rate the quiz Send feedback By WordPress Quiz plugin