'atoms' cannot 'react' to air pressure for air pressure is generated from atoms (oxygen, noble gasses, water).
Because the atoms of air molecules move slower when the weather is cold, thus making the air pressure to lower.
Air pressure is the weight of all the air above you. The higher you go, the more air is below you.
When a piece of copper is heated in the presence of air, it can react with oxygen to form copper oxide. This can result in an increase in weight due to the addition of oxygen atoms from the air to the copper atoms.
Atoms of non-metals usually gain or share electrons when they react with other atoms.
Short answer:A vacuum is actually a description of very low pressure.Long answer:This question really depends on the case. For this answer I'll be referring to an air cylinder like in a paintball gun or so on. Air pressure is the pressure or force a gas exerts on an object. For example atmospheric air pressure is the weight of all the air in the atmosphere above you pushing down on you. Or in the case of a cylinder pressure is the force of the molecules and atoms of air bumping into the wall of the cylinder. the more collisions with the walls the higher the pressure. Adding more air means more atoms to bump around and more pressure. As you start to remove the atoms and molecules from the cylinder there are less and less to bump into the walls. Thus lowering the pressure of the cyclical. A vacuum is reached when there are little to no more molecules or atoms bouncing around inside the tube. Therefore a vacuum is actually a description of very low pressure.
ruptured lungs from the sudden drop in air pressure
Because there is no air and thus no pressure that would hold your atoms together
they react to change because the fule works better in types of air pressure and humidity so the fule changes the cars gas mileage
atoms
This depends on the ability to gain/loss electrons.
Atoms of non-metals usually gain or share electrons when they react with other atoms.
In a high pressure area, the hot air balloon will tend to float lower as the surrounding air is denser and exerts more pressure on the balloon. This can cause the balloon to descend unless the pilot adjusts the temperature of the air inside the balloon to maintain altitude.