Conduction / Convection Problem !!!

a) Through the walls i.e. through a solid. Conduction is heat transfer through solids, like when you're stirring some soup with a wooden spoon - if you did it with a metal spoon, the heat would conduct up the metal and burn your hand and it would hurt. So you use a wooden spoon.

b) Hmm... I'm guessing that's conduction again, because like the spoon and the soup, the hot air is directly in contact with the hot radiator. Though I'm not certain on that one. Conduction is (as my dear physics teacher tried to explain) like a disco, with heat transferred by atoms bumping into each other when they're in direct contact. Like a disco in that the people dancing are close to each other and so bump into each other - he tried to demonstrate... Never mind. Anyway, It's usually solids, though... but here it says that the air is in contact with the radiator, so I'll guess conduction.

c) This one's a classic convection. Convection takes place in fluids (i.e. liquids and gases), a typical example being a radiator heating up a room and the heat being transferred through the air in the room. The air near the radiator heats up and becomes less dense, causing it to rise. As it goes 'along the ceiling' and further from the radiator, it cools and so it becomes more dense again, so it sinks. Then it goes 'along the floor' and reaches the radiator again, etc. That's a convection current.

Hope that helps.