Why does a solid change to liquid when heat is added?
the spacing between particles decreases.
particles lose energy.
the spacing between particles increases.
the temperature decreases.

The spacing between particles increases.

Explanation:

Solids is the state of matter in which the atoms of the matter are closely packed by the strong forces.

When solid is converted to liquid, these force has to be broken in order for the conversion to take place.

Thus, on heating the molecules gain energy and posses kinetic energy and start vibrating and moving. This energy overcome the forces of attraction and the spacing of the atoms decreases and turns into liquid.

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

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