Why does a metal melt when heated?

Answer 1

A metal will melt if heated to a high enough temperature.

Metal atoms are bonded together in a solid metal by forces that are derived from the difference in charge between a metal ion and an electron. In metals, rather than the particles that make them up being atoms, the atoms themselves split into positive ions and free negative electrons that are free to move between the metal ions. This is why metals are good conductors - the electrical charge can easily flow because of the free electrons that carry it.

When a metal is heated, the ions that make up the metal vibrate more and more as the temperatire increases. There comes a time when the amount of energy given to the metal is enough that the energy of vibration is more than that which holds the ions together, and so the ions too become free moving as the bonds between them break. As these are able to flow freely too, the metal becomes fluid - we say that it 'melts' forming a liquid.

There are a few metals which have very weak forces holding the particles together. Some mixtures of metals, like the alloy called 'Wood's Metal' will melt if placed in hot water. Gallium, for example, will melt if placed in a warm hand, and Mercury, of course, is already melted at room temperature, being the only metal that exists as a liquid at room temperature. Other metals have much stronger bonds between atoms and therefore have higher melting ponts. A good example of this is tungsten which has a melting point in excess of 3000 degrees Celsius - over half the temperature of the surface of the sun.

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Answer 2

It goes in fire for a very long time then you will notice the slight change in the shape of this metal.

ADDED: Bit more than "slight change in shape"! A complete phase change, no less. :-) The question actually asks "how" metal melts: the heat energy weakens the metal's internal, molecular bonds.

Answer 3

When you heat any substance, you are providing energy to the molecules. This energy allows the molecules to move within space. Even under stable conditions, all molecules have their own intrinsic energy used for vibration of bonds and molecule as a whole. Providing excess energy allows more movement, making the spaces between the molecules increase. Imagine a crowd in which people are making random jerky motions. The crowd will start getting more dispersed - the same happens in a substance. The molecules start moving away from each other, which is what translates to a liquid state.

Answer 4

Metals are melted so that they can be made into useful objects. They are also melted so that they can be made into a form that is easier to store and transport.

Answer 5

To reshape it and/or turn it into an alloy for further processing.