The wiki entry stated that the blood will boil if we were to be put in a vacuum. But boiling is defined as liquid turned into a gas. That is usually associated with an increase in temperture. The temperture inside a vacuum is lower than when in 1atm (due to less particle collisions) so why should the blood boil? Is it due to blood atoms being able to more freely move but where do they get the energy that allows them to do that? Or is it that blood has a vapour pressure (which is an indirect measure of how stable the chemical bonds are within the molecule and also dependent on the temperture of the environment) of say 0.5atm so it needs to be in an enviornment of 0.5atm to keep it in a liquid state. if the surrounding pressure is lower than 0.5atm than liquid blood will turn to gas because there is not enough force keeping them in the liquid form anymore. Alternatively if the temperture in the environment is increased, than the vapour pressure will decrease to a point where it might be less than the surrounding pressure, in which case it will boil. But it is the former point which is what the article is getting at? I have used terms in physics which I do not fully understand so please correct me if need be.