Apositron is a particle similar to an electron, but with the opposite charge of an electron. if a positron and an electron collide, sometimes both the electron and positron disappear, and two photons are created. this is an example of

Annihilation of matter

Explanation:

Matter is annihilated when it collides with its antiparticle leading to a tremendous release of energy. This contradicts the law of conservation of matter which states that matter can neither be created nor destroyed.

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