Air and Respiratory System

2. Oxygen supports _________ (combustion).
6. There are many tiny ______ in our lungs to allow gases to be exchanged.
8. ______ turns cloudy when carbon dioxide is blown into it.
9. The most abundant 78% of air is _______.
10. Earth is able to support life due to this layer of air called _____.
11. Plants need this air to make food.
13. The sticky liquid found in our nose and on the walls of our windpipe.
16. This muscle beneath our lungs moves upwards or downwards when we inhale or exhale.
17. The ______ in our nose traps dust of the inhaled air.
18. Our lungs _______ when we inhale as air rushes in from the nose or mouth.
20. Our ______ moves inwards and downwards when we exhale as air is forced out of our lungs.

1. 21% of inhaled air is _______.
3. Oxygen is always ________ in the surroundings as plants make food to give this air out.
4. Fish exchange gases when dissolved oxygen passes through their _____.
5. Humidity is the amount of ______ in the air.
7. Exhaled air is ______ than inhaled air due to our body temperature.
12. Energy is released when oxygen is breathed in and carbon dioxide is given out during ______.
14. Inhaled air is cleaned, warmed and ________.
15. Gaseous exchange happens in our ________.
19. Moving air is _____.