Unless there is some sort of poison in the air or if you have severe respiratory problems, no. In fact, some cases humid air can help breathing and 'loosen up' the throat and lungs.
No they can't breath air.
No. It is more instinctive for to breath through our noses because where far more air can get from the harmful substances in the air that us. Plus it takes less effort than breathing through your mouth
Humid air is more dense.
Yes, humid air is heavier than dry air because water vapor molecules in humid air add to its overall weight.
The moisture in the air makes it more stuffy and harder to breath humid as most people call it it effect's the weather by making it hotter.
Humid air has more water vapor mixed in it than dry air has.
No, humid air is not a solvent. A solvent is a substance capable of dissolving other substances, while humid air is simply air with a high moisture content.
Yes, there is less oxygen in humid air compared to dry air.
Moisture (water droplets) is saturating the air when the weather is humid.
If it is hot humid air, the air will be filled with a lot of moisture, and your hands feel all sticky and when you breathe, the air feels thick. But when it's cold humid air, the air has less moisture and it may feel easier to breath in. But it still has the same humidity as the hot air, you just feel it different. This is because when you say the air is humid, you are basically saying that the air has moisture in it. But the air always has moisture in it, but you can feel it when there is high humidity. So when it is cold air, you feel the humidity less. Because if it is hot air, that means the sun must be out, and when the sun is out, it evaporates the sweat and moisture off your skin and goes into the air. That is why in a crowded room, we describe the air as 'stuffy' because it is filled with the body heat from all the people in the room. I hope I answered your question properly. :)
Warm air
When the air is humid and the glass is cold.