How does the vacuum between the inner and outer walls of a thermos bottle limit energy loss through conduction and convection? 

By having no solid matter between the walls (like styrofoam) conduction is eliminated since conduction requires matter to be in contact with other matter.  The vacuum state eliminates convection since that is the heating of gas that then carries the energy to another body by traveling there and exchanging heat with it.

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Amethod of procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses.