1. Warm air vents are often placed near the floor in each room of a house. Why? (What transfer of heat is used in these, and how do they warm up the rooms?)2. A student makes an electrical current out of a battery, a length of wire, and an iron bar. What should the student do to increase the strength of this current? 3. Can atoms be independent? (Not mixed with anything and not on anything?)
(1) Air registers are sometimes located at floor level on the theory that warm air will rise by convection. (It's actually done to save ducting, but the principle applies). The air in the room is pulled through a heat exchanger where it is heated by conduction and then returned. The warm air radiates some of it's heat, but this heat transfer mechanism is negligible in your example. (2) The student has very few options for increasing current other than minimizing the resistance of the circuit or increasing the batteries voltage. Wrapping the wire around the iron bar will generate magnetism in the bar, but will not increase current. (3) Noble gases meet the requirement of independent atoms, as do some others.
