1. a scientific hypothesis can become a theory if
a) the entire community accepts it
b) the hypothesis is tested extensively and competing hypothesis are eliminated
c) there are no other competing hypothesis
d) the hypothesis can be tested at least once
2) a preliminary untested explanation that tries to explain how or why things happen in the manner observed is a scientific
a) law
b) theory
c) fact
d) hypothesis

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e

i believe the answer is a.