Alex Stalock made 27 saves for the Blackhawks (24-40-6), who have lost two straight.
"I thought we skated with them pretty good in the first period, but I think their strength and speed kind of pushed us back," Chicago coach Luke Richardson said. "We had some chances, but unfortunately we couldn't get that one to kind of keep our momentum going and keep us in that game. And then I think the power-play goal (in the second period) really kind of took the life out of our team tonight, and that third period we were trying. We were trying to skate early, but again, I think just us trying to press, we turned some pucks over, and that just fed their offense. They're good team, and I think we did some good things against them, but we're just not there yet to do it all game consistently."
Kurtis MacDermid gave the Avalanche a 1-0 lead at 2:41 of the first period when his cross-corner dump-in from the point redirected in off the knee of Ian Mitchell. It was his first goal of the season (38th game).
"He was dangerous tonight. Missed the net on a couple coming downhill on the weak-side flank," Bednar said. "'Dermy,' we got a little jolt out of the bench when he scored, no question."
Malgin extended the lead to 2-0 at 6:17 of the second period, scoring past the outstretched glove of Stalock from below the right face-off circle after taking a return pass from Valeri Nichushkin on a rush.
"I had good speed, I think, through the middle," Malgin said. "I saw [Nichushkin]. I just dropped the puck and went to the net, and he made a really good move, kind of like faked it and passed it to me. And I saw the net was open and just put it in."
Rantanen pushed it to 3-0 at 10:54 with a shot blocker side from the right circle on a power play. He has 13 points (six goals, seven assists) during an eight-game point streak.
"No. 1, he's in the lineup every night," Bednar said of Rantanen. "No. 2 is he's finding a way to get on the score sheet. It's a great year for him."