chemical equations and reactions

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Across
  1. 4. the eating away of metals
  2. 5. the addition of oxygen or removal of hydrogen
  3. 6. the addition of hydrogen or removal of oxygen
Down
  1. 1. ______gas is flushed into fried materials to prevent rancidity
  2. 2. decomposition reaction due to light
  3. 3. to agree to the law of conservation of mass, a chemical equation has to be______