'Hard' in the Bible

Have I not wept for those who have fallen on hard times?Has my soul not grieved for the needy?

can you help God spread out the skiesas hard as a cast metal mirror?

when water becomes as hard as stone,and the surface of the watery depths is frozen?

Can you depend on it because its strength is great?Would you leave it to do your hard work?

His heart is as hard as a rock,as hard as a lower millstone!