If your daughter is holding the shower head and some water accidentally gets on the glass, I would say "she splashes the glass". But if she deliberately points the shower head at the glass then I would say "she squirts water at the glass". "Squirts the glass" is not quite correct because it is the water that squirts, not the glass. Don't walk on the floor because it is wet. Literally, 'To light something up' means to shine a light on it. Metaphorically, you might say "when she smiles, her face lights up" Or, "I love her - she lights up my life". 'Ignite' is similar to "set fire to" but you wouldn't use it very often. When a rocket is launched into space, the rocket engines ignite. But you wouldn't ignite the engine in your car (you would light it) and you would not ignite a fire (you would light it -but you would not light it up) . But you might ignite a blow torch. So, 'ignite' has a sense of starting an explosion. She's soaking her feet in the water. Perfect. "I don't need any help thank you - I am quite able to do it myself". Or, "I am quite capable of doing this myself thank you." So, yes, the two words can sometimes be used interchangeably. If a member of staff is very efficient I might say "That person seems very capable". But if a child is very clever I would say "She is very able". So, in this example 'capable' has more of a sense of physical ability rather than mental ability. If you drink so much that you are unable to walk, the police can arrest you for being "drunk and incapable". "I am not able/unable to swim" means "I can't swim but I could learn" but "I am not capable of swimming" has the sense of "I can't swim and would never be able to learn" . It is somehow more definite.