I was snowmobiling through Yellowstone National Park and made a stop at the world famous Old Faithful Geyser. The family and I stood in two feet of snow in the frigid winter air watching as hot water and steam gushed from Old Faithful like a jet engine gone mad! Immediately I had an idea - to try to build a geyser in the lab to show the principles of how Old Faithful works; this is what I came up with.
How to make a geyser with liquid nitrogen
1 liter soda bottle
Alternate Supplies for making a geyser at home
1 liter soda bottle
Soda bottle cap (with hole large enough for straw)
Straw or tubing to reach from cap to bottom of bottle (glue straw inside hole of cap)
-Cut a piece of tubing or a straw so it will extend from the bottom of the bottle, through the opening and about 2 inches above the top. Push the tubing through a rubber stopper or through the cap of the soda bottle (make a hole by heating a nail and poking it through. Continue until hole is large enough).
-Fill the soda bottle with liquid nitrogen until it is about 1/3 full. Push the tubing and stopper firmly on the top and watch as the liquid nitrogen comes shooting out the top of the bottle!
How does the liquid nitrogen geyser work?
The gas laws of chemistry and physics explain that a liquid takes up less space (less volume) than a gas. If the liquid turns to a gas it will take up more space (more volume) than it did when it was a liquid. In our experiment, the liquid nitrogen sits at the bottom of the bottle and is steadily turning into a gas (nitrogen gas). When the bottle is not capped off, the expanding gas flows up through the top of the bottle and escapes. When we place a cap on the bottle, the gas cannot escape.
As more of the liquid nitrogen turns from a liquid to gas more space is needed because, as stated before, gas takes up more space. The pressure builds and the gas above the liquid begins to push out in all directions. Because there is a tube in the liquid, the increased gas pressure pushes down on the liquid and into and up the tube causing liquid nitrogen to be shot out of the bottle! This is our model geyser!
How do geysers work?
According to the National Park Service:
"Geysers are hot springs with constrictions in their plumbing, usually near the surface, that prevent water from circulating freely to the surface where heat would escape. The deepest circulating water can exceed the surface boiling point (199°F/93°C). Surrounding pressure also increases with depth, much as it does with depth in the ocean. Increased pressure exerted by the enormous weight of the overlying water prevents the water from boiling. As the water rises, steam forms. Bubbling upward, the steam expands as it nears the top of the water column. At a critical point, the confined bubbles actually lift the water above, causing the geyser to splash or overflow. This decreases pressure on the system, and violent boiling results. Tremendous amounts of steam force water out of the vent, and an eruption begins. Water is expelled faster than it can enter the geyser's plumbing system, and the heat and pressure gradually decrease. The eruption stops when the water reservoir is depleted or when the system cools."
Learn more about geysers here: https://www.nps.gov/yell/learn/nature/geysers.htm
So, if you can't make it to Yellowstone National Park to experience Old Faithful (and the countless other geysers in the Park) just bring the park into your home or school with a little liquid nitrogen and a soda bottle! Do some experimenting by changing the size of the bottle or the amount of nitrogen or the diameter of the tube.
If you are interested in Yellowstone and the Supervolcano that lies within the park, check out some clips from the HISTORY Channel special hosted by Craig Beals titled "Secret Earth: Yellowstone Supervolcano" (click here).
Keep on Learnin'
Caution: Liquid nitrogen is dangerous because it is -320 degrees F (-190 degrees C). It can cause severe frost bite, burns or severe damage to eyes and other tissue. It should only be handled by adults who are wearing appropriate safety gear.