What is the mass number of an atom that has six protons , six electrons and eight neutrons

14

Explanation:

Given parameters:

Number of protons  = 6

Number of electrons  = 6

Number of neutrons = 8

Unknown:

Mass number  = ?

Solution:

The mass number of an atom is the sum of protons and neutrons in an atom;

 Mass number  = number of protons + number of neutrons

 Mass number  = 6 + 8  = 14

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

- decrease the number of plants and animals living in the water.