A solid substance turns directly into a gas. Which term describes this change? deposition
evaporation
melting
sublimation

Sublimation.

Since evaporation is liquid into gas, melting is solid into liquid and deposition is the geological process where sediments are added to land forms.

sublimation

Explanation:

i just did on edgen :)

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.