2. State whether the following are chemical/physical changes. a. Rubbing alcohol evaporates on your hand b. Gasoline is ignited c. You take in antacid to settle your stomach d. Milk goes sour e. Photosynthesis f. Boiling of water g. Freezing of water i. Rusting of iron

A is physical

B is chemical

C is chemical

D is chemical

E is chemical

F is physical

G is physical

I is chemical

Explanation:

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.