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Why can a tiny scratch defeat a strong piece of glass?

A piece of glass can be strong yet vulnerable to a small surface flaw. A scratch can concentrate the effects of a load, while strengthening treatments try to make cracks harder to open at the surface.

3–5 min

Questions you could explore

  • How is resisting a scratch different from resisting the growth of a crack?

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  • CorningHow It Works: Strengthening Glass

    The manufacturer explains ion exchange and surface compression as a way to preserve strength after small surface damage. Its product claims are distinct from the underlying mechanism.

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Chemistry and materials

What does hard water leave behind in a kettle?

Water can carry dissolved minerals without looking cloudy. Hardness mainly describes calcium and magnesium in solution, while limescale is a deposit that can form when processes such as heating change the balance.

3–5 min

What does hard water leave behind in a kettle?

Chemistry and materials3–5 minWater can carry dissolved minerals without looking cloudy. Hardness mainly describes calcium and magnesium in solution, while limescale is a deposit that can form when processes such as heating change the balance.

Chemistry and materials

Why does ice take up more room than water?

An ice cube floats in the water it came from, and freezing water can push against its container. Ordinary ice arranges water molecules differently from the liquid, connecting a microscopic pattern with a familiar change in volume.

3–5 min

Why does ice take up more room than water?

Chemistry and materials3–5 minAn ice cube floats in the water it came from, and freezing water can push against its container. Ordinary ice arranges water molecules differently from the liquid, connecting a microscopic pattern with a familiar change in volume.

Chemistry and materials

How can light reveal an element you cannot touch?

A glowing gas can produce a pattern of spectral lines characteristic of its elements. Comparing several lines gives more evidence than spotting one color or one line alone. Scientists use spectra to investigate distant objects, while temperature, motion, and other conditions also affect what they observe.

5–7 min

How can light reveal an element you cannot touch?

Chemistry and materials5–7 minA glowing gas can produce a pattern of spectral lines characteristic of its elements. Comparing several lines gives more evidence than spotting one color or one line alone. Scientists use spectra to investigate distant objects, while temperature, motion, and other conditions also affect what they observe.

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