About a decade ago, I wrote briefly about the interesting experiment of throwing boiling hot water into air that is below -18°C (0°F) (see Ice Clouds).
WARNING: If trying this experiment on your own, be certain to NEVER throw boiling water into the wind. Make sure the water is thrown with the wind, away from you. Doing so not only keeps you safe but also creates a much more magnificent effect. Also, having the cloud backlit by the sun helps to accentuate the beauty of the experiment as well.
During a particularly cold snap here in Michigan, I repeated these experiments with some family members (Video 1).
Video 1: Boiling Water vs. Cold Air, Tommy Technetium YouTube Channel (accessed 1/16/24)
Why does throwing boiling hot water into cold air cause ice clouds? After doing the experiments this time around, I thought in a bit more detail about how this happens. The main thrust of the effect is the evaporation of water followed immediately by its rapid and immediate condensation:
H2O(l) → H2O(g) Eq. 1
H2O(g) → H2O(l) Eq. 2
Why do these steps (Equations 1-2) occur in rapid succession? I estimate that by the time we got the water off the stove and outside, it cooled to about 90°C, which means its vapor pressure was near 525 mmHg. This is over 20 times higher than the vapor pressure of water at room temperature (about 20 mmHg)! Naturally, a lot of water easily evaporates from the hot water into the cold, dry air (Equation 1). However, this gaseous water very quickly begins moving through the frigid air where it cools and recondenses back into tiny liquid microdroplets of water (Equation 2). In fact, some of these the microdroplets become so cold that they go on to freeze into tiny particles of ice:
H2O(l) → H2O(s) Eq. 3
So you get all three phases of water in a single, strikingly beautiful experiment (Equations 1–3)! What’s more, the tiny microdroplets of ice and water create stunning, steamy striations that streak from the hot liquid blobs.
Surface tension is another aspect of this experiment that I wondered about. The surface tension of water at 90°C is 61 J m-2, which is about 15% lower than the surface tension of water at room temperature (73 J m-2). I think about surface tension of a liquid as the energy required to spread the liquid out over an area (you can see this from the units of surface tension – joules per meter squared). The lower surface tension of water allows it to break apart and spread out into streams and tiny blobs much easier than water at room temperature. This separation spreads the hot liquid out, increasing its surface area in contact with the air. This higher degree of surface area contact between hot liquid and cold air translates into a greater volume of stunning icy striations streaking through the air.
I suppose it’s not at all surprising that chemistry is intimately involved in this experiment. After all, chemistry has a funny way of making everything a bit more beautiful.
Safety
Safety: Video Demonstration
Safety: Video Demonstration
Demonstration videos presented here are not meant as tools to teach chemical demonstration techniques. They are meant as a tool for classroom use. The demonstrations may present safety hazards or show phenomena that are difficult for an entire class to observe in a live demonstration.
Those performing the demonstrations shown in this video have been trained and adhere to best safety practices.
Anyone thinking about performing a chemistry demonstration should first read and then adhere to the ACS Safety Guidelines for Chemical Demonstrations (2016) These guidelines are also available at ChemEd X.
General Safety
General Safety
For Laboratory Work: Please refer to the ACS Guidelines for Chemical Laboratory Safety in Secondary Schools (2016).
For Demonstrations: Please refer to the ACS Division of Chemical Education Safety Guidelines for Chemical Demonstrations.
Other Safety resources
RAMP: Recognize hazards; Assess the risks of hazards; Minimize the risks of hazards; Prepare for emergencies
NGSS
Asking questions and defining problems in grades 9–12 builds from grades K–8 experiences and progresses to formulating, refining, and evaluating empirically testable questions and design problems using models and simulations.
Asking questions and defining problems in grades 9–12 builds from grades K–8 experiences and progresses to formulating, refining, and evaluating empirically testable questions and design problems using models and simulations.
questions that challenge the premise(s) of an argument, the interpretation of a data set, or the suitability of a design.
Scientific questions arise in a variety of ways. They can be driven by curiosity about the world (e.g., Why is the sky blue?). They can be inspired by a model’s or theory’s predictions or by attempts to extend or refine a model or theory (e.g., How does the particle model of matter explain the incompressibility of liquids?). Or they can result from the need to provide better solutions to a problem. For example, the question of why it is impossible to siphon water above a height of 32 feet led Evangelista Torricelli (17th-century inventor of the barometer) to his discoveries about the atmosphere and the identification of a vacuum.
Questions are also important in engineering. Engineers must be able to ask probing questions in order to define an engineering problem. For example, they may ask: What is the need or desire that underlies the problem? What are the criteria (specifications) for a successful solution? What are the constraints? Other questions arise when generating possible solutions: Will this solution meet the design criteria? Can two or more ideas be combined to produce a better solution?
Planning and carrying out investigations in 9-12 builds on K-8 experiences and progresses to include investigations that provide evidence for and test conceptual, mathematical, physical, and empirical models.
Planning and carrying out investigations in 9-12 builds on K-8 experiences and progresses to include investigations that provide evidence for and test conceptual, mathematical, physical, and empirical models. Plan and conduct an investigation individually and collaboratively to produce data to serve as the basis for evidence, and in the design: decide on types, how much, and accuracy of data needed to produce reliable measurements and consider limitations on the precision of the data (e.g., number of trials, cost, risk, time), and refine the design accordingly.
Students who demonstrate understanding can plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes.
More information about all DCI for HS-ESS2 can be found https://www.nextgenscience.org/dci-arrangement/hs-ess2-earths-systemsand further resources athttps://www.nextgenscience.org.
Students who demonstrate understanding can plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes.
Emphasis is on mechanical and chemical investigations with water and a variety of solid materials to provide the evidence for connections between the hydrologic cycle and system interactions commonly known as the rock cycle. Examples of mechanical investigations include stream transportation and deposition using a stream table, erosion using variations in soil moisture content, or frost wedging by the expansion of water as it freezes. Examples of chemical investigations include chemical weathering and recrystallization (by testing the solubility of different materials) or melt generation (by examining how water lowers the melting temperature of most solids).