What, if any, is the difference between the motion of sliding and swiping? For example you may adjust the volume control by sliding the indicator, but to unlock your phone I think most people refer to it as swiping? Is it correct to say the term "swiping" implies a greater degree of difficulty and is used in situations where you don't want the event to be accidentally triggered e.g. turning off an alarm?
The best example of a slider as you have mentioned is a volume control. it is defined as "move smoothly along a surface while maintaining continuous contact with it."
Whereas the swiping action is defined as "hit or try to hit with a swinging blow."
The swiping action is only used in few places where the actions will not cause any major changes in the functionality, for example swiping to change the image from the image gallery. where as sliding is used in almost all the places like the ON/OFF button's and even in iPhone unlock its slide function for the reason not to be triggered accidentally.