Velocity specifies speed, while speed includes a specific direction. Velocity specifies a change in speed over time, while speed specifies a change in distance over time. Velocity specifies a change in distance over time, while speed specifies a change in velocity over time
The number before any molecular formula applies to the entire formula. So here you have five molecules of water with two hydrogen atoms and one oxygen atom per molecule. Thus you have ten hydrogen atoms and five oxygen atoms in total.
