Question

When a substance gains electrons in a chemical reaction, the substance is said to be activated. dissociated. reduced. oxidized?

Answer 1

Reduced is the right answer. You can remember it like that if it gains electron that means it will turn negative or will get reduced nuber. So itis reduction
Ihope it will help:)

Answer 2

It is reduced
for example:-

when water is electrolised

H2O --->   2H+ +O- 

- the oxygen atom gains an electron and is reduced to O-