Avacuum flask keeps its contents warmer or cooler than the surrounding environment for a length of time. it consists of two flasks, one inside the other, that connect at the neck. the space between the two flasks is completely empty of air. what does the design of the vacuum flask m inimize heat transfer by conduction?

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.