The openings are called stomata.
The stomata are openings in plant leaves through which gasses pass in and out. During the day carbon dioxide passes from the air through the stomata to the leaves and oxygen, produced by the leaf, passes back out through them. At night plants yield up small amounts of carbon dioxide through the stomata.
As with other plants, leaves are where the tree carries out photosynthesis to produce food. Leaves are also used to regulate the plant's temperature through water evaporation and exchange various gasses (oxygen, carbon dioxide, etc) needed/created by different internal processes.
Coke leaves the body in 72 hours.
yes
A bullet leaves a gun barrel because it is forced out by the pressure of burning gasses.
Through chemical reactions, yes.
Liquids can through evaporation, and solids can through combustion.
Arteries usually carry gasses such as oxygen throughout the blood. The gasses are then diffused through capillary beds to be used as nutrients by tissues in the body.
Longitudinal (also know as compression) waves travel more slowly through gasses than solids.
The bullet is quickly pushed out of the barrel by rapidly expanding gasses from the burning gunpowder. Those expanding gasses push the air when the bullet leaves the gun, making a POP or POW or BANG.
no
Intake valves are cooled by the gasses passing through them, exhaust valves are heated by the gasses passing through them and can be burned by overheating.