(1) According to the actual situation, the material of motor drill must have the characteristics of high hardness; The energy conversion in the working process of the motor includes two aspects, namely, consuming electric energy, converting the motor into mechanical energy and heating the heater into internal energy.

Therefore, the answer is: high hardness; Electrical energy is converted into mechanical energy and internal energy.

(2)①Q absorption =cm(t-t0)=4.2× 103J/(kg? ℃)× 1.5kg×( 100℃- 15℃)= 535500j

②15min = 900s, 2min =120s.

The electric energy consumption of the electric heater is: w1= p1t1= 750w× 900s = 675000j.

The electric energy consumed by the motor is: w2 = p2t2 =180w×120s = 21600j.

Therefore, the electric energy consumed in the whole process is w = w1+w2 = 675000j+21600j = 696600j.

Answer: ① The heat absorbed by water and soybean milk is 535,500 J; ② The electricity consumption for the whole process is 696600J J. ..