18. when we conduct an experiment the condition we are investigating the one thing we want to know about is called the
a. question
b. hypothesis
c. control group
d. variable
19. the group of experimental subjects that is left “natural” or left unchanged is called the
a. control group
b. experimental group
c. hypothetical group
d. testable group
20.the group of experimental subjects that has the one condition changed is the
a. control group
b. experimental group
c. hypothetical group
d. testable group
21. when the experiment is complete the researcher
a. starts another experiment
b. researches new questions
c. analyzes the data and comes to a conclusion
d. repeats the experiments for validity

18. When we conduct an experiment the condition we are investigating the one thing we want to know about is called the:

b. hypothesis - we are conducting the experiment in order to validate or invalidate the hypothesis

19. The group of experimental subjects that is left “natural” or left unchanged is called the:

a. control group - we need to have a reference point for our experiment to check if something has changed, how much have been changed or if have not changed at all.

20.The group of experimental subjects that has the one condition changed is the:

b.experimental group - on this grump we make changes and compare the results with the control group

21. When the experiment is complete the researcher:

c. analyzes the data and comes to a conclusion - after experiments the data are analyzed to see if the hypothesis is proved of not.

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.