1. Air is a   Liquid   Gas   Solid   Plasma   Hint Half-n-half Clue   2. Carbon dioxide is lighter than air.   True   False   3. Nitrogen constitutes nearly __ % of the atmosphere.   79   21   57   42   Half-n-half Clue   4. When hydrogen peroxide acts on Manganese Dioxide, oxygen is produced.   True   False   5. Air is   A Mixture   An Element   A Compound   An Alloy   Half-n-half Clue   6. Which gas in the atmosphere saves us from the UV rays of the sun?   Ozone   Carbon Monoxide   Nitrogen   Oxygen   Half-n-half Clue   7. A hygroscopic substance is one which   Releases water   Absorbs air   Absorbs water   Releases air   Half-n-half Clue