In Physics buoyancy is the upward force and it is equal to the weight of the displaced fluid. If the buoyancy exceeds the downward force (which is the weight of the boat) due to gravity then the object floats. Therefore the displaced fluid determines how much you can load on a boat. When the weight is bigger than the buoyancy (the weight of the displaced water) the boat will sink.

A red sock is a compound. An element consists of only one kind of atom. A compound consists of two or more different elements that bond together. A mixture consists of two or more elements or compounds that are physically intermingled. This means they can be separated again by physical means (centrifugation, evaporation, magnets, chromatography, etc.)

Frost is the sublimation of water vapor on your windshield that has a temperature below freezing. Sublimation means that the water vapor (gas) goes from gas to solid (ice crystals) without going through the liquid stage.