Water DOESN'T Freeze At Zero Degrees?! | BBC Earth Kids

Summary

In this video, Maddie reveals a surprising truth about the freezing point of water. While we're taught that water freezes at 0°C, the actual freezing point of pure water can be as low as -48°C. This is due to the need for a nucleation point, like dust or other impurities, to trigger the formation of ice crystals. The phenomenon of supercooling, where water remains liquid even below freezing, can be dangerous for airplanes. When supercooled water comes into contact with a plane, it instantly freezes, causing inflight icing that can reduce lift and control, making ice protection systems essential for safe flights.

Takeaways

• 😀 Water doesn't always freeze at 0°C; supercooling can occur under certain conditions.
• 😀 Water needs a nucleation point (e.g., dust, ice particle) to start freezing.
• 😀 Pure water, when supercooled, can remain liquid even at temperatures as low as -8°C.
• 😀 The actual freezing point of pure water can be as low as -48°C.
• 😀 Supercooling can occur in nature, with liquid water found as cold as -40°C in clouds.
• 😀 Supercooled water presents a risk to airplanes flying through certain clouds.
• 😀 When supercooled water contacts a plane, it rapidly freezes, forming ice on the aircraft's surfaces.
• 😀 This phenomenon, called inflight icing, can cause ice to form on the leading edges of wings, nose, and tail.
• 😀 Inflight icing reduces lift and increases drag, which can threaten a plane’s control and stability.
• 😀 Modern airplanes are equipped with ice protection systems to counteract the risks of inflight icing.
• 😀 Flight planning takes into account the potential for supercooled water to ensure aircraft safety.

Q & A

Why is the freezing point of water not always 0°C?

The freezing point of water can vary due to the presence of impurities or the lack of nucleation points that help start the crystallization process. In pure water, freezing can occur at much lower temperatures.

What is needed for water to freeze into ice?

For water to freeze, the H2O molecules must be arranged in a crystalline structure. This process typically requires a nucleation point, which can be provided by an impurity, a dust particle, or another ice crystal.

What is supercooled water?

Supercooled water is water that remains in liquid form even when its temperature drops below the normal freezing point of 0°C, due to the absence of nucleation points in the water.

At what temperature does pure water freeze?

Pure water can freeze at temperatures as low as -48°C, far lower than the typical freezing point of 0°C, if it lacks nucleation points.

How do nucleators help in the freezing process of water?

Nucleators, such as impurities, dust, or other ice particles, provide a surface for ice crystals to grow on, helping to kickstart the freezing process.

How can supercooled water be dangerous to airplanes?

Supercooled water in clouds can freeze upon contact with the surfaces of an airplane, leading to ice buildup. This ice can alter the airflow over the plane, reducing lift and increasing drag, which can result in a loss of altitude and control.

What is inflight icing?

Inflight icing occurs when ice forms on the surfaces of an airplane, typically on the wings, nose, or tail, as a result of supercooled liquid water in the atmosphere freezing on contact.

Why is ice formation on an airplane a safety concern?

Ice formation on an airplane disrupts airflow, reducing lift and increasing drag, which can compromise the aircraft's ability to maintain altitude and control, posing significant safety risks.

How do modern aircraft prevent ice formation?

Modern aircraft are equipped with ice protection systems designed to prevent or mitigate ice buildup on critical surfaces like the wings and tail.

What measures are taken during flight planning to avoid inflight icing?

Flight planning includes ensuring that aircraft avoid flying through areas with supercooled liquid water or other conditions that could lead to inflight icing, reducing the risk to safety.