1. Which of the following is necessary for a substance to burn?   Gasoline   Oxygen   Light   Hydrogen   Hint Half-n-half Clue   2. Dry ice is   Any Frozen Liquid   Very Cold Ice   Ice with salt added   Solid Carbon Dioxide   Half-n-half Clue   3. Which of the following is not a constituent of the atmosphere?   Carbon Dioxide   Nitrogen   Aluminum   Oxygen   Half-n-half Clue   4. When we breathe which of the following gases do we use?   Helium   Oxygen   Carbon Dioxide   Hydrogen   Half-n-half Clue   5. Nitrogen constitutes nearly __ % of the atmosphere.   57   42   79   21   Half-n-half Clue   6. A barometer is used for measuring   Humidity   Atmospheric Pressure   Temperature   Annual Rainfall   Half-n-half Clue   7. Air is   An Element   A Compound   An Alloy   A Mixture   Half-n-half Clue