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A metal alloy that is liquid at room temperature.

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One fun thing you can do right away with the liquid metal alloy is make your own mirrors. All it takes is a piece of glass and a cotton swab.

Cotton swabs are coated with liquid metal


Dip the cotton swab in the vial, and twirl it around to coat it with the liquid metal alloy.

Liquid metal coated on glass

Now rub the coated swab on the glass (in the phot we are using a glass microscope slide). The metal sticks to the glass, and makes an opaque reflective coating.

More fun things

There are lots of things you can do with liquid metal:

  • Make thermometers
  • Make barometers
  • Make tilt meter seismographs
  • Make non-conductive objects conductive
  • Make electrodes that conform to varying surfaces
  • Experiment with magnetohydrodynamics
  • Wiggle it with high frequency electricity
  • Use it to conduct high energy sound
  • Replace mercury in spinning telescope mirrors

If you need a shiny surface, a dilute solution of hydrochloric acid can be placed on the surface, or you can use a light coating of mineral oil. Both will prevent the slow oxidation of the metal that occurs over time.

How does it do that?

Gallium is an element (atomic number 31, right below aluminum and just to the right of zinc in the periodic table of the elements). It starts out with a very low melting point already, but we can add some other elements to get an even lower melting point.

Right below gallium in the periodic table is indium (element 49). Just to the right of indium is tin (element 50).

When these elements are combined, their atoms bind together into a compound. The molecules of that compound do not bind to one another as much as the atoms of the original metals bound to each other. This lowers the melting point.

There are many ways to combine the three metals:

Combining three metals

Each combination will have a slightly different melting point. Which do you think has the lowest melting point? This might make a good science fair experiment.

A mixture of 76% gallium and 24% indium melts at 16° Celsius (61° Fahrenheit). Both gallium and this combination can be supercooled. That means that once melted, they can stay liquid even though they are cooled well below their melting points. Eventually a small crystal forms, and starts the whole batch solidifying, but small amounts can be kept supercooled for quite a while.

The gallium-indium alloy is more reflective than mercury, and is less dense, so it is being explored as a replacement for mercury in spinning liquid mirrors for astronomical telescopes.

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