Download Claudia Livingston Physics 1010 Physics Individual Project By

Claudia Livingston
Physics 1010
Physics Individual Project
By definition the boiling point of a substance is the temperature at which the vapor
pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a
vapor. Have you ever wondered if you could get water to boil on the moon or if it would just
simply disintegrate? In order to understand the theories behind it, it is important to understand
the environment first.
Air does not exist on the moon and therefore the moon has zero atmospheric pressure and
is considered a vacuum. Without pressure it would be very hard to keep water molecules together
and trap heat. On the sunlit side of the moon the water would boil and then turn into a gaseous
state very quickly. As the pressure decreases the boiling point also decreases. On the shaded side
of the moon the water, when exposed to the atmosphere, would instantly freeze and vaporize.
The boiling point of water can be decreased until the triple point is reached. The triple
point refers to the stable thermodynamics equilibrium, it is the temperature and pressure at which
a given substance coexists in the three phases (gas, solid, and liquid). In other words the triple
point is the minimum pressure that liquid water can be present. In outer space or on the moon for
that matter solid water or ice, below the triple point, when heated at a constant temperature and
pressure will cause sublimation. Sublimation occurs when a substance changes directly from a
solid to vapor without reaching the liquid stage.
The figure above demonstrates the points at which a liquid, solid, and gas exist in
corresponding temperatures in relation to pressure. The solid green line refers to the difference
between the solid and liquid phases by melting and freezing points. The blue line represents the
liquid to gas phase and shows the rates at which condensation and vaporization occur. The red
line divides the solid and gas points on the diagram representing sublimation and desublimation.
The critical point on the graph refers to the point at which it is impossible to differentiate the
liquid and gas substances.
The liquid water will immediately hit sublimation. In a matter of less than a second the
vapor will turn into a solid through a process called desublimation. Desublimation is the opposite
of sublimation in which the gas turns directly from a gaseous state into a solid without passing
through the liquid phase.
To understand how water boils here on earth in comparison to on the moon may help us
to understand the temperature in relation to atmospheric pressure. The boiling point of water is
100 degrees Celsius or 212 degrees Fahrenheit at an atmospheric pressure of 101.325 kPa. On
the top of Mount Everest the boiling point of water is 71 degrees Celsius or 159.8 degrees
Fahrenheit at 33.597 kPa.
1 kPa (Kilo Pascal) = 1000 Pa(Pascal) = 1000 n / m^2 (kPa refers to units of stress or pressure)
It’s safe to say that water boils on the moon but, it happens very rapidly through
sublimation. Due to the zero atmospheric pressure the liquid water will vaporize and disintegrate
extremely quickly. Due to this rapid process the boiling point doesn’t really apply past the triple
point!
Works Cited
1. "Triple Point." Wikipedia. Wikimedia Foundation, 30 Oct. 2013. Web. 04 Nov. 2013.
2. "Boiling Point." Wikipedia. Wikimedia Foundation, 11 Apr. 2013. Web. 04 Nov. 2013.
3. Twietmeyer, Ted. "Moon Water Creates An Atmosphere Problem." Moon Water Creates An
Atmosphere Problem. Rense, 24 Sept. 2009. Web. 04 Nov. 2013.