1. Dry ice is   Ice with salt added   Solid Carbon Dioxide   Any Frozen Liquid   Very Cold Ice   Hint Half-n-half Clue   2. The lower, dense region of the atmosphere is known as   Stratosphere   Hydrosphere   Troposphere   Ionosphere   Half-n-half Clue   3. Carbon dioxide is lighter than air.   True   False   4. When we breathe which of the following gases do we use?   Carbon Dioxide   Hydrogen   Helium   Oxygen   Half-n-half Clue   5. A hygroscopic substance is one which   Absorbs water   Releases water   Absorbs air   Releases air   Half-n-half Clue   6. Lime water turns milky after carbon dioxide is passed through it.   True   False   7. Nitrogen constitutes nearly __ % of the atmosphere.   21   42   57   79   Half-n-half Clue