Teaching students about the boiling point of helium may seem like a daunting task, but with the right approach, it can be a fascinating and enlightening experience. Helium, a noble gas, is one of the most abundant elements in the universe, and its properties are truly remarkable.
The boiling point of helium, also known as the temperature at which it changes from a liquid to a gas, is -268.9°C or -452°F. This makes helium the coldest liquid known to man. It can only exist as a liquid at extremely low temperatures and pressures, which occur primarily in outer space.
Introducing students to the concept of boiling point can be done in a variety of ways. For younger students, a simple demonstration using water and a hot plate is a great starting point. Begin by adding water to a boiling pot over the hot plate. As the water heats up, they will be able to see it beginning to bubble and boil. Explain that this is the water reaching its boiling point.
Once the students have a basic understanding of the concept, it’s time to introduce helium. Start by explaining that helium is a gas that can only be turned into a liquid at extremely low temperatures and pressures. Show them a picture of the Helium II (liquid helium at the boiling point) phase diagram to demonstrate the pressure and temperature range at which it can exist as a liquid.
Next, walk them through the process of cooling helium down to its boiling point. You could freeze a balloon filled with helium in a liquid nitrogen bath or use a liquid helium cryostat to show students how to reach the required temperature.
To help students visualize the unique properties of liquid helium, there are many excellent educational videos that demonstrate the effects of the helium II phase. For example, helium II has zero viscosity, which means that it can flow without resistance, and it exhibits superfluidity at very low temperatures, leading to remarkable phenomena such as quantum vortices.
Finally, acknowledge the use of helium in science and technology, such as in MRI machines and in rocket engines. Encourage students to think about how advancements in cold temperature research can lead to future technological innovations.
