In the diagram, planets A, B, and C have the same mass. Which of these statements is true about the motion of these planets? A. Planet A will take the longest time to complete an orbit, while planet C will take the shortest time. B. Planet A will take the shortest time to complete an orbit, while planet C will take the longest time. C. The combined gravity of planets A and C will cause planet B to take the longest time to orbit. D. All the planets will take the same amount of time to complete one orbit.

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

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.