Scottish Premiership Wrap: Hearts suffer another defeat, Ross County hold Partick
The striker was on target five minutes before half-time at Tynecastle on Saturday to ensure that the Edinburgh outfit remain on minus two points after starting the season in administration.
Victory for Stuart McCall's third-placed side ensured that they cut the gap to Aberdeen above them in second to just one point, and the Fir Park club have a game in hand.
The result marked a sixth consecutive win for Motherwell, while bottom side Hearts have now lost three in a row and are now 20 points adrift of second-bottom Ross County.
Filip Kiss marked his debut with two goals as County fought back to secure a point by holding Partick Thistle to a thrilling 3-3 draw.
Midfielder Kiss, signed on loan from Cardiff City this week, put the visitors in front at Firhill but a double from Lyle Taylor gave Partick the advantage at half-time.
Steven Lawless gave the hosts breathing space two minutes after the restart, but Ben Gordon pulled a goal back three minutes later and Kiss salvaged a point before substitute Stuart Kettlewell was shown a late red card for the visitors following a challenge on Ross Forbes.
Goals from Murray Davidson and Stevie May gave St Johnstone a 2-0 home victory over St Mirren in the other Premiership game to be played on Saturday.
St Johnstone leapfrogged Hibernian into sixth spot as a result of that win, while St Mirren occupy ninth spot.