Too many objects inside a laboratory fume hood can disrupt the airflow and possibly compromise you safety. Which of the following are considered best practices in the use of a laboratory fume hood? a. Open the sash as much as possible
b. Work at least 25 cm inside the hood
c. Use fast, quick movements to limit your exposure
d. Place objects to one side—work on other side
e. Use a raised along the back of the hood

Open the sash as much as possible and Place objects to one side-work on other side

The sash must to remain open as much as possible so that the harmful fumes goes outside through it and place objects to one side and work on other side at a certain distance from the chemical reaction. The fumes releases from a chemical reaction are harmful that can severely damaged the body of the researcher so these two methods can be used in order to reduce the damages.

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