1. Sometimes, I go outside - to go shopping.
2. Sometimes, I go outside to go shopping.
(In Sentence 1, "-" is used before 'to go.' Is #1 grammatical? What is the difference between #1 and #2?)
Use only sentence 2. That is not a correct use of the hyphen.
Both Sentence 1 and Sentence 2 are grammatical, but they have slightly different meanings and implications.
In Sentence 1, the dash ("-") is used before "to go" to indicate a pause or interruption in the sentence. It acts as a break to emphasize the action of going outside separately from the purpose of going shopping. This construction suggests that going outside is an independent activity, and going shopping is an additional detail or reason for going outside.
In Sentence 2, there is no dash, and the phrase "to go shopping" is connected directly to the sentence. This implies a stronger connection between going outside and going shopping. The purpose of going outside in this sentence is primarily to go shopping, and the two activities are seen as closely related.
So, the main difference between Sentence 1 and Sentence 2 is the level of emphasis and the perceived relationship between going outside and going shopping. Sentence 1 separates the two actions more distinctly, while Sentence 2 presents them as more closely connected.