Which statement is true for a cooling curve? a.) it shows how the temperature of the substance falls as heat is removed. b.) it shows how the temperature of the substance changes when heat is applied. c.) it shows the increase in the average kinetic energy of the particles. d.)it shows how heat absorption affects the motion of particles. e.) it shows how energy gain causes the temperature to fall.

The best answer is A) It shows how the temperature of the substance falls as heat is removed. 

The cooling curve shows how the temperature of a substances changes with time, as it is allowed to cool. The substance is first heated until completely liquefied, and then allowed to cool. The flat parts of the curve, where temperature is constant with time, show the periods in which the state of matter of the substance changes. One the substance completely changes it state of matter, namely changes from liquid to solid, its temperature continues to drop. 

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B.1 - hydrogren-1 can only mean there is 1 neutron. it's obvious there is 1 proton or else it wouldn't be hydrogen, so they wouldn't put a number after it unless they were indicating the number of neutrons