The answer for first one is sulphur reason :
Sulphur has a specific gravity of 2. That means if you were to weigh a 2kg lump of Sulphur under water (i.e. WET) it would have an apparent weight of only 1kg. All things weigh more when they burn (oxygen gets added). Sulphur has an atomic number of 16. If it combines with oxygen (atomic number 8) on a one-to-one basis, it will weigh 1 1/2 times as much, That means 2kg will weigh 3kg.
And the answer for second one is odd numbers that is once a year that means 1 it's a odd number coming once a year and In a month 4 weeks will be there in which 2 weeks are odd they 1st. Week and 3rd week. And In a week 7 days are there in which 1,4,5,7 days are odd numbers and in a day 12 hours are there in which 1,3,5,7,9,11 are odd.