Firstly, it should be noted that the freezing point of a substance can be assumed to be melting point of that substance because a substance will normally change from liquid to solid (freezes) at the same point it changes from solid to liquid (melts). For example, water freezes at 0°C and also starts melting at 0°C.
Thus, the substance with the lowest melting point among the substances mentioned in the question is alcohol (ethanol) with the melting point of -114°C. Hence, <u>ethanol also has the lowest freezing point thereby freezing at the lowest temperature.</u>
Engineers have designed experimental cars that use liquid hydrogen for fuel instead of gasoline. this is an example of Substitution.
Substitution is the process where one thing replaces other for a particular purpose. here liquid hydrogen is replacing the gasoline for fuel in car. hence the correct word to fill is Substitution.
