We FINALLY Proved Why Ice Is Slippery

Summary

This video delves into the perplexing slipperiness of ice, a property that has puzzled scientists for centuries. It explores various theories, from the presence of a thin liquid layer to the pressure-induced melting of ice underfoot. Recent research using atomic force microscopy reveals a quasi-liquid layer on the ice's surface, where loosely bound molecules move with a freedom unusual for solids but not quite liquid. The video uncovers the complex interplay of molecular structure, temperature, and friction that makes ice uniquely slippery, challenging our understanding of this common material.

Takeaways

• 🧊 Ice exhibits an unusual property where two blocks can fuse together momentarily, raising questions about its solid-state behavior.
• 🤔 The slipperiness of ice has been a topic of debate for over 160 years, with its surface behavior being particularly perplexing.
• 🔬 Recent research using an atomic force microscope (AFM) has provided the first detailed images of ice's surface at the atomic level.
• 🌡️ The temperature and pressure conditions can significantly affect the slipperiness of ice, with different winter sports favoring specific temperatures.
• 📉 James Thompson's work on the phase diagram of water showed how temperature and pressure affect the state of ice, contradicting the simple liquid layer theory.
• 🛷 The theory that pressure from ice skates melts the ice to create a slippery layer was debunked by experiments showing that the pressure is not sufficient to melt ice.
• 🔥 The idea that friction-generated heat melts the ice surface was considered but is not the primary cause of ice's slipperiness.
• 🔍 Researchers discovered a quasi-liquid layer at the surface of ice, where water molecules are loosely bound and can move more freely than in the solid state.
• ❄️ The surface of ice is composed of hexagonal and cubic ice types, with the boundary between them creating a disordered region that contributes to slipperiness.
• 🌍 This unique behavior of ice being slippery as a solid but less so when a liquid layer forms is a fascinating characteristic of one of Earth's most abundant materials.

Q & A

Why do two blocks of ice fuse together when held in contact for a short time?

When two blocks of ice are held together, the water molecules at the surface of the ice can interact and form hydrogen bonds, leading to the fusion of the two blocks into a single object due to the unique properties of ice.

What is the unusual property of ice's surface that contributes to its slipperiness?

The unusual property of ice's surface is the presence of a quasi-liquid layer. This layer is composed of loosely bound water molecules that are not as rigid as the solid ice beneath them, allowing for movement that contributes to the slipperiness of ice.

Why was it historically thought that ice was slippery due to a thin layer of liquid water on its surface?

In the late 1850s, Michael Faraday conducted experiments that led him to conclude that the slipperiness of ice was due to a thin layer of liquid water on its surface. This theory was supported by the observation that water creates a slippery barrier when spilled on a floor.

What problem arises with the theory that ice is slippery because of a thin layer of liquid water?

The problem with this theory is that ice remains slippery even under extreme vacuum conditions where no liquid layer can be present, as liquid water molecules would have evaporated away due to the lack of atmospheric pressure.

What is the role of atmospheric pressure in the melting of ice?

Atmospheric pressure can affect the melting point of ice. As pressure increases, the melting point of ice decreases, which is why ice can melt under the pressure exerted by an ice skate blade, creating a slippery layer of water.

Why is the idea that pressure alone causes ice to melt insufficient to explain its slipperiness?

The idea that pressure alone causes ice to melt is insufficient because the actual pressure exerted by a person on ice skates is not enough to significantly lower the melting point of ice. Moreover, light objects or those with a larger surface area should not slip at all if pressure were the sole factor.

What is the phenomenon known as 'pre-melting'?

Pre-melting is the process that occurs before solid ice melts into liquid water. It involves changes in the mobility of the topmost water molecules on the ice surface as the temperature increases, leading to a change in the slipperiness of the ice.

How does the slipperiness of ice change with temperature?

The slipperiness of ice is temperature-dependent. It is found to be most slippery at around -7°C, which is the typical temperature used in speed skating rinks. As the temperature decreases further, the ice becomes less slippery.

What technique was used by researchers to visualize the surface of ice at the atomic level?

Researchers used an atomic force microscope (AFM) to visualize the surface of ice at the atomic level. This technique is sensitive enough to detect the space between individual atoms and can produce detailed images of the ice's surface.

What did the AFM images reveal about the structure of the ice surface?

The AFM images revealed that the ice surface has a quasi-liquid layer with loosely bound water molecules that are oriented in a disordered manner. These molecules are held by a reduced number of hydrogen bonds and can move with a freedom not usually experienced by a solid.

Why doesn't the AFM tip drag water molecules along as it scans the ice surface?

The AFM tip does not drag water molecules along as it scans the ice surface because the experiment was conducted at a very cold temperature (-150°C), where the slippery water molecules are 'frozen' in place, allowing for a clear image to be captured without the molecules moving around.