Minimal Pairs /ɑ:/ and /ɜ:/
fast and first
Below are lists of words that vary only by one having the vowel sound /ɑ:/ and the other the vowel sound /ɜ:/. You can use this to practise the sounds or as a list of words to be careful to pronounce properly.
This page uses the symbols of the Phonemic Chart. You can listen to the symbols here.
Both sounds are long single sounds but the mouth position is different, with /ɑ:/ having a much wider open mouth position. This is why your doctor asks you to say this sound to show him or her inside your mouth. /ɜ:/ is much more like the sound people make when they are disgusted.
* the meaning of the word is not important at this level, but it can still be used to contrast the pronunciation with the other word.