Identify each energy exchange as primarily heat or work and determine whether the sign of δe is positive or negative for the system. a. sweat evaporates from skin, cooling the skin. (the evaporating sweat is the system.) b. a balloon expands against an external pressure. (the contents of the balloon is the system.) c. an aqueous chemical reaction mixture is warmed with an external flame. (the reaction mixture is the system.)

the transfer of heat by electromagnetic radiation is called thermal radiation . it is usually carried out by electromagnetic waves in an energy range just below the visible spectrum, which is the infrared range.

so the answer would be radiation.

: )

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.