To determine the correct statement based on the map shown, let's analyze each option in relation to the provided map.

1. Option 1: "The library is located to the northwest of the canteen."
   • The library is situated to the west of the physics lab and north of 5th Cross Road.
   • The canteen is located to the east of the 1st Main Road and north of the hospital.
   • Since the library is to the northwest of the canteen, this option is correct.
2. Option 2: "The hospital is located to the east of the chemistry lab."
   • The hospital is located to the north of the chemistry lab across the 1st Main Road.
   • Since east means directly parallel and right, this statement is not correct, as the hospital is actually to the north of the chemistry lab.
3. Option 3: "The chemistry lab is to the southeast of physics lab."
   • The chemistry lab is to the south of the 5th Cross Road, whereas the physics lab is to its north.
   • It is situated southeast relative to the physics lab on the map, making this statement correct.
4. Option 4: "The classrooms and canteen are next to each other."
   • The classrooms are located to the west of the chemistry lab and south of the hostels.
   • The canteen is north of the hospital, and therefore, they are not next to each other.

Based on the analysis above, the correct statement is: "The chemistry lab is to the southeast of physics lab."