Purdy and club colleague Tom Price were among the England replacements forb the second match of the tournament in France, with both appearing the second half against the defending champions.
England trailed 21-0 at one point but fought back in the second period to claim a losing bonus point before switching focus to their last Pool A clash against USA on Thursday.
Centre Harry Sloan and lock Elliott Stook joined Purdy on the scoresheet, with fly-half Henry Slade kicking nine points.
England coach Nick Walshe said: “We gave ourselves a mountain to climb in the first half and at 21-0 down we knew it would be tough, but credit to the guys – they dug deep and came very close to pulling it back.
“We’re not out of the competition, we will have to rely on a couple of results going our way but we all we can do is focus on playing well against USA on Thursday.”
England Under-20s
15 Anthony Watson (Bath Rugby)
14 Ben Howard (Worcester Warriors)
13 Harry Sloan (Harlequins)
12 Sam Hill (Exeter Chiefs)
11 Jack Nowell (Exeter Chiefs)
10 Henry Slade (Exeter Chiefs)
9 Alex Day (Northampton Saints)
1 Danny Hobbs-Awoyemi (Northampton Saints)
2 Luke Cowan Dickie (Exeter Chiefs)
3 Scott Wilson (Newcastle Falcons)
4 Elliott Stooke (Gloucester Rugby)
5 Dominic Barrow (Leeds Carnegie)
6 Ross Moriarty (Gloucester Rugby)
7 Matt Hankin (Saracens)
8 Jack Clifford (Harlequins) (c)
Replacements:
16 Scott Spurling (Saracens)
17 Alec Hepburn (London Wasps) for Hobbs-Awoyemi 58 mins
18 Tom Smallbone (London Irish)
19 Tom Price (Leicester Tigers) for Barrow 58 mins
20 Joel Conlon (Exeter Chiefs) for Hankin 65 mins
21 Callum Braley (Bristol Rugby) for Day 44 mins
22 Ollie Devoto (Bath Rugby)
23 Henry Purdy (Leicester Tigers) for Watson 40 mins
