At the top of the mountain you feel more colder than the normal temperature.
sea level
Sea level
At sea level
The air has the weight of all the air above it pressing down on it. this compresses the air increasing its density. So air at sea level is more dense than air on the top of the mountain, since the air on the mountain top has less air above it pressing down.
the air on the top of the mountain is more thinner because there is less pressure compared to what is going on, on sea level
That would depend where you are. The weight of air above you is greater at sea level than up a mountain, but if you were in a plane it might well be less than up a mountain.
on the bottom of the mountainbeacause you are more below air level
Yes.
yes, as you go farther up from the sea level, the air will become thinner.
It is the effect of air pressure. The air pressure at the top of a mountain is less than the air pressure at sea level. The effect of air pressure on a water surface is to prevent or oppose water molecules escaping from the surface. The greater the air pressure, the more heat energy is needed to allow the water molecules to escape and so at sea level the water will boil at a higher temperature than if it were on top of a mountain.
Air pressure decreases as height is gained. There is less air pressure at the top of a high mountain, than at sea level.
Air is denser at lower altitudes and less dense at higher altitudes. If the bottom of the valley is directly below the mountain, at a lower altitude, then there is technically more air in the valley.