Scientists are studying how substance a and substance b react. when substance a and b are mixed, a substance different from a and b floats to the top of the solution. this is evidence that a(n). physical change occurred. endothermic change occurred. irreversible change occurred. chemical change occurred.

answermeridional ;

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.