Drugs are drugs that act on the nervous system to alter states of consciousness, modify perceptions, and change moods.

Psychoactive drugs are the drugs that act on the nervous system to alter consciousness, modify perceptions, and change moods. 

Hope this helps!

The answer to this will be from your lab notes/procedure. it would be best to ask another student who participated in the lab as we do not know what was done, what enzyme or if the temperature is celsius or fahrenheit. if i were to guess though i'd say the rate stopped due to enzyme denturing at high temperature