1. Which is heavier—a water molecule, , or a carbon dioxide molecule, ? 2. When we breathe we inhale oxygen, , and exhale carbon dioxide, , plus water vapor,  Which likely has more mass—the air that...

1. Which is heavier—a water molecule,
, or a carbon dioxide molecule,
?

2. When we breathe we inhale oxygen,
, and exhale carbon dioxide,
, plus water vapor,
 Which likely has more mass—the air that we inhale or the same volume of air that we exhale? Does breathing cause you to lose or gain weight?