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