When a metal is heated its density decreases. there are two sources that give rise to this decrease of rho: (1) the thermal expansion of the solid and (2) the formation of vacancies (section 5.2). consider a specimen of gold at room temperature (20°c) that has a density of 19.320 g/cm3 . (a) determine its density upon heating to 800°c when only thermal expansion is considered. (b) repeat the calculation when the introduction of vacancies is taken into account. assume that the energy of vacancy formation is 0.98 ev/atom, and that the volume coefficient of thermal expansion, αv is equal to 3αl .

At 20∘c, the hole in an aluminum ring is 2.800 cm in diameter. you need to slip this ring over a steel shaft that has a room-temperature diameter of 2.804 cm . 1. to what common temperature should the ring and the shaft be heated so that the ring will just fit onto the shaft? coefficients of linear thermal expansion of steel and aluminum are 12×10−6 k−1 and23×10−6 k−1 respectively.

Beryl states that insulation with the smallest possible thermal conductivity is best to keep a house warm in winter, but worst for keeping a house cool in summer. sapphire insists the reverse is true: low thermal conductivity is good in the summer, but bad in the winter. which one, if either is correct? a. beryl, because low thermal conductivity results in low heat transfer. b. beryl, because low thermal conductivity results in high heat transfer. d. sapphire, because low thermal conductivity results in high heat transfer. e. neither, because low heat transfer is desirable both in summer and in winter.

Which is an example of an exothermic process?