If the temperature of water continuously decreases but it is not given room to expand, it will eventually contract and form exotic forms of ice that sink in liquid water.

How freeze-drying leaves food with less than 4% of its original water content

In specialized equipment, foods are brought down to temperatures below freezing before a vacuum pump removes the air from the container, lowering the pressure around the food and the boiling temperature of water. Heaters beneath the food slowly raise its temperature above the now-reduced boiling point, causing the water to go from a frozen to a gaseous state.

Explaining the Leidenfrost effect, where water can hover and move against gravity

Water droplets can glide across surfaces whose temperatures are well above water's boiling point. This heat instantly vaporizes the bottom of the droplet, creating a layer of steam that the rest of the droplet rides and bounces upon. This can be seen when sprinkling water on skillets to determine if the surface is hot enough to cook on.

Freezer burn is the result of moisture leaving ice cream, something that's easily avoidable.

High freezing speed restricts the development of gritty crystal chunks in ice cream

For this reason, ice cream does not maintain its smoothness when refrozen in a traditional freezer over several hours. The smooth texture is also made possible by balancing fat, sugar, and emulsifiers.

Hail forms in freezing temperatures thousands of feet above the ground

Even if surface temperatures are well above freezing during the summer, updrafts during thunderstorms can push raindrops high into the atmosphere, where they can freeze and form hail. Giant hailstones the size of softballs require updrafts of close to 100 mph.

Fish in polar waters contain proteins in their blood that act as antifreeze, and some manufacturers have used lab-grown versions of these proteins to help keep ice cream smooth.

Under certain conditions, very hot liquids can freeze more quickly than cooler ones—a phenomenon called the Mbemba effect, after the Tanzanian high school student who accidentally observed it.

Different types of ice link water molecules together in unique shapes

The ice used to cool drinks—Iₕ—is composed of H₂O molecules arranged in hexagonal structures. This structure forms as ice expands during freezing, providing additional space between molecules, lowering the overall density, and allowing it to float in water. Under sufficient pressure, this spacing can collapse in many ways, creating new forms of ice.

Permafrost—soil, rocks, and sand that are held together by ice and remain frozen for at least two consecutive years—covers about 15% of the Northern Hemisphere's land area.

Is ice slippery because of amorphization—a chaos of molecules caused by sliding?

Traditional explanations cite three factors that make ice slippery: pressure, friction and so-called premelting. A fourth has been proposed in recent years: amorphization, that sliding along some surfaces creates molecular disorder, causing liquid-like behavior.

How the loss of Earth's atmosphere would cause oceans to boil at freezing temperatures

Many phenomena requiring air pressure, from the flight of birds and aircraft to the act of breathing, would no longer be possible. Because sound travels through vibrating air molecules, the loss of the planet's atmosphere would also create a silent environment. Even during daytime hours, the sky would resemble a clear night sky.

Tiny water droplets can blur a rainbow's colors into a foggy white

When sunlight enters water droplets, it can reflect from the inside and spread out into different colors, producing a series of colorful arcs—supernumerary bows—which we refer to as rainbows. For droplets a few hundredths of a millimeter in size, these arcs overlap onto each other, producing fogbows of white light.

Our bodies cool us down by sweating because water requires a significant amount of energy to change state from liquid to gas, making it an ideal medium for carrying thermal energy away from our bodies.

The conditions needed for cloud iridescence, or rainbow clouds

The relatively rare phenomenon occurs when sunlight scatters off tiny water droplets or ice crystals in thin, newly-forming or semi-transparent clouds, such as altocumulus, cirrocumulus, lenticular, and cirrus varieties. This effect is similar to what is seen in soap bubbles and mother-of-pearl shells and produces pastel-like colors.

Snowflakes form when water vapor turns directly into ice

Every water molecule has a slightly bent shape due to electron repulsion and regularly forms bonds with hydrogen molecules. When they freeze, they form a six-sided (or hexagonal) lattice, resulting in the six-sided symmetry of snowflakes. As the snowflake falls, more water molecules freeze onto its six sides, forming the unique, beautiful geometric designs.

A guide to making ice cream with liquid nitrogen by flash-freezing dairy

Only existing in liquid form at extremely low temperatures, nitrogen can rapidly freeze cream, coconut milk, and other liquids into small crystals, producing smooth, creamy ice cream. As a safety precaution, liquid nitrogen should be handled in a well-ventilated area with safety goggles and protective gloves.

'Watermelon snow'—patches of pink, orange, and red in snow—is the result of extremophilic green algae that thrive in extremely frigid conditions and take the shape of red spheres in winter.

A history of treating frostbite

Amid Napoleon's invasion of bitterly cold Russia, soldiers succumbed to frostbite by the thousands. Nineteenth century doctors recommended walking and rubbing snow around the affected area. Fast forward to recent years, and the FDA has approved its first ever drug to treat frostbite. Listen to this podcast to learn the history of this wintry affliction.

Photochemical smog forms when sunlight reacts with car and industrial emissions

The hazy phenomenon's name is a combination of "smoke" and "fog" and is composed of chemical pollutants that can cause eye irritation, lung damage and harm to crops. Smog buildup is more common in cities with sunny climates, minimal wind and surrounding mountains that trap these chemicals.

The forgotten carnivals that stood upon the frozen River Thames

The Thames Frost Fairs were unusual winter events that took place between 1607 and 1814. They happened during the so-called Little Ice Age, when the River Thames would freeze over for up to two months straight. These unique festivals transformed the frozen river into a bustling carnival-like environment where Londoners set up temporary shops, entertainment venues, and social spaces directly on the ice.

Ice cream’s unfrozen consistency is thanks to sugar

Making ice cream is a complex, multistep scientific process. But the treat’s scoopable, chewable consistency is due to the product’s dissolved sugar.

Although PFAS, or forever chemicals, are intentionally designed to be extremely stable and long-lasting because of their strong carbon-fluorine bonds, these bonds can be broken by heat, plasma, and supercritical water.

What causes hail?

Hail can be a particularly destructive element of certain thunderstorms, occurring even during otherwise warm days. Learn about the dynamics that lead to ice chunks falling from the sky.

Once cooled to temperatures just above 2 Kelvin, helium atoms exhibit a quantum property that removes internal friction, allowing the fluid to climb up walls.

Learn all about different types of extreme weather

Find out in more detail about different types of extreme weather, from flooding to thunderstorms, from tropical cyclones to sandstorms, and more (w/ helpful videos).

Niagara Falls generates its own microclimate

Constant mist from the Falls produces localized weather effects, including rare ice formations that can rise over 100 feet high in winter.

An overview of extremophiles and the biochemical adaptations employed by various types

These organisms thrive in environments that would normally be inhospitable to most living things by using molecules that help counter deadly environmental factors. These include antifreeze-like proteins that prevent psychrophiles from freezing and rupturing in polar regions, and osmoprotectants that prevent some extremophiles from losing water to salty environments.

Why do flash floods occur?

Flash flooding can be more dangerous than traditional floods, occurring within the span of hours and exhibiting rapid currents. Here's how atmospheric conditions and geography combine to make some locations ripe for the disaster.

Ice cream, gelato, sorbet, and Italian ice are all popular cold desserts, though they have many important differences.

What is a heat dome?

The world is seeing regular heat waves with multiple causes, including so-called "heat domes," a term rising in use in recent years. A heat dome occurs when the atmosphere traps hot ocean air like a lid or cap, creating stifling conditions and resulting in extended periods of heat. See an illustration of this phenomenon and read how it works with this brief explainer.

How to survive hypothermia

Hypothermia is a deadly risk for those living in cold areas, causing around 1,500 deaths a year in the United States. Stay safe with tips from this article, which cites research papers to help prevent and treat the condition. Take note of the best fabric to wear when cold weather hits—not cotton but wool.

The composition of comets earned them the nickname 'dirty snowballs'

The icy relics of the solar system are composed of rock, gravel, dust, and frozen molecules, such as carbon dioxide, carbon monoxide, methane, ammonia, and water. Once close to the sun, these compounds sublimate into gases, creating a fuzzy cloud that earned the comets another nickname in history: hairy stars.

Lightning is the sudden flow of electricity in the atmosphere as two oppositely charged regions seek to become balanced via the movement of electrons.

The ingredients that make up severe weather

A seven-minute video illustrating how a storm is made. These factors—moisture, instability, lift, and shear—are explained through a series of data sets and creative, descriptive diagrams.

Simulations suggest ice's slipperiness comes from rearranging molecules

Past models have proposed that slipperiness arises from a thin layer of liquid water formed at the ice's surface by frictional melting. However, new research suggests that electromagnetic forces between interacting surfaces push water molecules out of an ordered, crystalline structure and into a shapeless, soft, slippery layer. This process occurs solely through contact, independent of pressure or friction.

Cloud formation requires water vapor and condensation nuclei to build from

The nuclei—particles like dust, salt, and smoke—act like jumpstarts that water molecules can start to accumulate onto to form clouds. Condensation nuclei are about 1/100th the size of cloud droplets, which are mostly water.