What is the independent variable in this lab?
temperature
distance
thermal conductivity
time
specific heat

time

Explanation:

time can be controlled and set while all the others can't be necessarily controlled

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

the answer is na (sodium)