When a pot of water is put on a stove, the water at the top gets hot primarily by
a. radiation
c. convection
b. conduction
d. condensation

certain materials can become superconductors under what conditions?
a. when it is very hot
c. under very high pressure
b. when it is very cold
d. under very low pressure

Answer
1. c. convection
2. b. When it is very cold

Explanation
Water like any other liquid transfer heat energy through convection. 

When a pot of water is put on a stove, the water at the top gets hot primarily by convection.

A supperconductor is a material that can conduct electric current with no resistance at all. 
The supperconductivity can be achieved under cooled temperatures. 

Certain materials can become superconductors under what conditions? When it is very cold

Learned about life itself

If the heat engine is a perfect carnot cycle engine, thenefficiency = (t2-t1)/t2   where t1=temperature of cold reservoir ( ° k) = 135            t2=temperature of hot reservoir ( ° k)   = 325thereforeefficiency = (t2-t1)/t2 = (325-135)/325 = 0.5846 = 58%  note: this is the theoretical maximum efficiency of a perfect heat engine.   real-life engines do not achieve this value.