It is said that we should use 'while' for 'age' or 'periods of life.'

What are periods of life? Would you name 'periods of life'?

1. When I was 15, I went to Chicago.
2. While I was 15, I went to Chicago.
(Is #2 wrong?)

3. When I was in middle school, I sold newspapers.
4. While I was in middle school, I sold newspapers.
(Can we use both 'when' and 'while'?)

5. I felt happy when I was a kid.
6. I felt happy while I was a kid.
(What about these sentences?)

I'd use "while" when referring to a range of years. Example:

While I was a teenager, I went to Chicago.

Thus I'd say 1, 3, 4, 5, and 6 are fine, but 2 doesn't read quite right.

Yes it's wrong

Periods of life refer to specific stages or phases in a person's life. Here are some common examples: childhood, adolescence, young adulthood, middle age, and old age.

Regarding the sentences you provided:

1. "When I was 15, I went to Chicago." - This sentence is grammatically correct. "When" indicates a specific point in time in the past.

2. "While I was 15, I went to Chicago." - This sentence is also grammatically correct. "While" is used to indicate that an action occurred during a certain period of time, which in this case is when the speaker was 15.

So, both sentences (1 and 2) are correct, but they have slightly different meanings. Sentence 1 emphasizes the specific age (15), while sentence 2 emphasizes the duration of time in which the speaker was 15.

3. "When I was in middle school, I sold newspapers." - This sentence is grammatically correct. "When" is used to indicate a specific period of life (middle school) and is appropriate in this context.

4. "While I was in middle school, I sold newspapers." - This sentence is also grammatically correct. "While" is used to indicate that an action occurred during a certain period of time, which in this case is when the speaker was in middle school.

Both "when" and "while" can be used to indicate periods of life, so both sentences (3 and 4) are correct.

5. "I felt happy when I was a kid." - This sentence is grammatically correct. "When" is used to indicate a specific period of life (kidhood or childhood) and is appropriate in this context.

6. "I felt happy while I was a kid." - This sentence is also grammatically correct. "While" is used to indicate that an action occurred during a certain period of time, which in this case is when the speaker was a kid.

Both "when" and "while" can be used to indicate periods of life, so both sentences (5 and 6) are correct.