When Clark and Pete first meet Cyrus, they're in their science class. After Chloe walks off, the viewers see Pete holding a soldering iron with his hands by the heater core (you can see the shine of the metal). If that soldering iron would've been plugged, Pete would suffer severe burns to his fingers.
When Jonathan and Martha finish their conversation about Martha's health in the storm cellar, Jonathan's mouth keeps on moving even though there's no sound.