Water cannot easily flow in these impermeable rocks.

水不容易流进那些不透水的岩石.

Conductors like metals and salt water tend to have loosely bound outer electrons, which can easily flow between molecules.

像金属和盐水一样的导体往往带有受到束缚较弱的外层电子，这些电子能够轻易在分子间流动。