Calorific value is determined using a bomb calorimeter, where a known mass of fuel is burnt in excess oxygen in a sealed bomb, and the heat released is absorbed by a known mass of water. Temperature rise is measured. Corrections for cooling, wire, and acid formation are applied. Units: kJ/kg or kJ/mol. The bomb calorimeter works at constant volume.
Explanation:
Boiling water changes state from liquid to gas, but the chemical composition (H₂O) remains unchanged – physical change. Others form new substances.
Explanation:
Iodine directly converts from solid to violet vapor on gentle heating (sublimation). NaCl melts; sugar decomposes; copper melts at high temperature. Other sublimable substances: camphor, naphthalene, dry ice.
Explanation:
Total electrons = 16 (Sulfur). Period = number of shells = 3. Valence electrons = 6, group = 10+6 = 16 (Group 16, chalcogens). Group 6 would be 6 valence electrons but in d-block, not applicable. Group 18 has 8 valence electrons (except He). So sulfur is in group 16, period 3.
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