if / in case

English as a Second Language English Vocabulary, Grammar and Idioms
1
  1. Give him this toy (if)/(in case) he cries.
  2. You should dial 999 (if)/(in case) there is a fire.
  3. I advise you to eat something now (if)/(in case) there is no food when we get there.
    Are all these sentences OK?
    Can we use ‘if’ and ‘in case’ interchangeably?
2

The sentences are all acceptable. ‘If’ is used as a possible condition and ‘in case’ is used in a possible situation.

Bring the washing inside if it rains = possible condition. In other words wait until it rains and then do it.

Bring the washing inside in case it rains = possible situation. In other words do it now as a precaution because I think it is going to rain.

Alan