Summary

In this demonstration, students will observe boiling water added to liquid nitrogen. This causes the liquid nitrogen to quickly evaporate and appear cloud-like as water vapor in the air condenses on the cold gaseous nitrogen.

Grade Level

High School School

NGSS Alignment

This demonstration will help prepare your students to meet the performance expectations in the following standards:

• MS-PS1-4: Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
• HS-PS3-2: Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motions of particles (objects) and energy associated with the relative positions of particles (objects).
• Scientific and Engineering Practices:
  • Developing and Using Models
  • Constructing Explanations and Designing Solutions

Objectives

By the end of this demonstration, students should be able to:

• Understand the relationship between temperature and phase changes.
• Describe how the behavior of particles changes based on the state of matter.
• Interpret their observations from the demonstration to explain what happened.

Chemistry Topics

This demonstration supports students’ understanding of:

• States of Matter
• Phase Changes
• Intermolecular Forces

Time

Teacher Preparation: 5 minutes
Lesson: 5 minutes

Materials

*Amounts have been reduced for a smaller-scale classroom demonstration.

• 800 mL liquid nitrogen
• 200mL of boiling water
• Heat source/Hot plate for heating water
• Container for the liquid nitrogen (~10 L, we used a small trash bin)
• Spill container/plastic bin
• Face shield
• Insulated gloves
• Lab coat

Safety

• Always wear safety goggles when handling chemicals in the lab.
• Students should wear proper safety gear during chemistry demonstrations. Safety goggles and a lab apron are required.
• Exercise caution when using a heat source. Hot plates should be turned off and unplugged as soon as they are no longer needed.
• Use caution when handling boiling water and liquid nitrogen, they can cause burns. Wearing insulated gloves is recommended.
• A large amount of nitrogen gas is formed during this demonstration, which can displace oxygen, therefore this demonstration should not be performed in a small, confined area. Only complete this demonstration in a well-ventilated area, or outdoors. 

Teacher Notes

• For more information about this demonstration and others like it, see the article, The Wonderful world of Chemistry: A Magic Show, published in the May 2022 issue of Chemistry Solutions.
• A video recording of this demonstration can be viewed at the 16:15 timestamp in the Magic Show video.
• This demonstration was originally completed as part of an outreach event and can be viewed in the video recording. In the procedure below, we have downsized the amounts of materials for use on a smaller scale. These recommendations listed below reduce the amount of liquid nitrogen and water by a factor of five from the original amounts used in the Magic Show event.
• Teacher Procedure:
  • Heat 200 mL of water to a near boil (90-99 °C).
  • Pour 800mL of liquid nitrogen into an empty plastic container placed on the ground.
  • Quickly, all at once, pour the hot water into the liquid nitrogen. This will cause a large cloud of water vapor to condense on the cold, gaseous nitrogen that evolves.
• Water may end up on the floor after the demonstration. To try to contain the spray of water, we placed the trash bin containing the liquid nitrogen into a plastic “kiddie pool.” We recommend using a spill container. While this helps, water still may end up on the floor, so it is helpful to have paper towels or spill pads nearby.
• This demonstration can be used to explain to students that almost all atoms and molecules can exist as solids, liquids, and gases depending on the temperature. In fact, the structure of the atom or molecule is directly related to the temperature at which a substance is a solid, liquid, or gas. That is why nitrogen, which does not interact strongly with itself, is a gas at room temperature but water, which interacts relatively strongly with itself, is a liquid.
• Variations in temperature can lead to a molecule changing from a solid to a liquid, or from a liquid to a gas. Using water as an example is helpful because most students have experienced it as a solid, liquid, and gas, in our natural environment. For example, when it is cold outside liquid water turns to ice (a solid), whereas when you heat water on the stove, it starts to boil as it becomes a gas.
• The billowing white cloud that is produced in this experiment from the cold nitrogen interacting with water sinks to the floor, because it is colder than air, and hotter gases rise because they are less dense.
• Suggestions for classroom discussions and student tasks related to this demonstration could include:
  • Formation of clouds in the atmosphere from condensed water vapor.
  • A comparison of the temperature of liquid nitrogen (-320 °F, -196 °C, 77 K) and boiling water (212 °F, 100 °C, 373 K) using different temperature scales.
  • Draw a particle diagram describing what happens when the water and liquid nitrogen are mixed in the demonstration.