What is the cause of air pressure?
6. Give two uses of air pressure. 7. Why may sand be used to put out a fire? 8. What substances do fires add to the air? 9. Why does the air enter the lungs when we inhale? 10. How does exhaled air differ from ordinary air? 11. What is meant by the statement that a sounding body is a vibrating body? 12. How does air help us to hear? 54 A TEST OF YOUR SKILL IN THE USE OF THE METHOD OF A SCIENTIST Read the description below at least twice before you try to answer the question which follows it. Two boys tried to see if they could show that exhaled air contains less oxygen than ordinary air. The first boy used one bottle and one candle. He lighted a new candle and lowered it properly into the bottle full of exhaled air and left it until it went out. He timed it to see how many seconds it burned. He then filled the same bottle with fresh air, relighted the candle, and repeated the experiment, using the same watch. Result: He found that the candle burned for a longer time in the bottle of ex
