The margin of victory is the largest of the tournament so far, with the two-time champions against a Moroccan team on debut at the tournament.
Popp scored her 63rd and 64th international goals, moving to third on Germany’s all-time list.
The Wolfsburg player quickly made her mark on the tournament after missing out on the final of the 2022 European Championship against England because of injury.
The second half featured two Morocco own goals sandwiched between goals from Klara Bühl and Lea Schüller. Morocco is the first Arab and North African country to qualify for the tournament.
In the 11th minute, Popp scored with a header off a cross from Kathrin Hendrich. She doubled her tally with another header in the 39th off Klara Bühl's corner kick.
Bühl scored the third goal with a right-foot strike just 23 seconds into the second half.
Germany’s fourth goal came in the 54th minute after Moroccan defender Hanane Aït El Haj deflected the ball into her own goal posts resulting from a cross by German midfielder Svenja Huth.
Another own goal by Yasmin Mrabet followed before Lea Schüller rounded out the scoring for Germany in the 90th minute.
After losing to Zambia and Brazil in recent friendlies, Germany announced itself as a contender to win the tournament with the comfortable victory. The 2003 and 2007 World Cup winners have advanced to at least the quarterfinals in each of its eight previous World Cup appearances. Germany is on top of Group H, with Colombia and South Korea set to play their opening match on Tuesday.
Morocco's lopsided loss on debut adds pressure to its remaining group-stage matches. It will be aiming to improve on this performance in order to keep its hopes alive of advancing to the tournament's knockout stage.
Germany will travel to Sydney for its next game against Colombia, who advanced to the round of 16 in its last World Cup appearance. Morocco will play South Korea at Adelaide’s Hindmarsh Stadium. Both games are scheduled for Sunday.