Minimal Pair initial /f/ and /p/
Below is a list of words that vary only by one having the initial sound /f/ and the other the initial sound /p/.
You can use this list to practise the sounds, or as a list of words to be careful in pronouncing.
/p/ is producing by building up the air and pressure behind lips that are squeezed together and then releasing it, similar to making a popping sound. This means that your mouth moves during the production of the sound and that it is impossible to extend the sound after your mouth is open and the air has been released.
/f/ is pronounced with your top teeth touching your bottom lip, and the sound can be extended for as long as you like without moving your mouth just by continuing to blow through the gap between those two parts of your mouth.