Does the surrounding air become warm or cool when vapour phase of h2o condenses? explain.

Will you chech and finish these for me, because i am stumped with them.

The rigid beam is supported by the three suspender bars. bars ab and ef are made of aluminum and bar cd is made of steel. if each bar has a cross-sectional area of 450 mm2, determine the maximum value of p if the allowable stress is (σallow)st = 200 mpa for the steel and ( σallow)al = 150 mpa for the aluminum. est = 200 gpa and eal = 70 gpa.

Give one example to show that when substances are mixed, it may result in a chemical or a physical change depending on the conditions.