What determines whether something is a solid, a liquid or a gas?

Can someone me with these questions plz.

The alkali metals (group 1) consist of lithium (3), sodium (11), potassium (19), rubidium (37), cesium (55), and francium (87). they are soft, metallic solids with low densities and low melting points. based on the data shown in figure 1, how many valence electrons do alkali metals share?

How does a hydroelectric power plant converts energy into energy.