Hola Eula
"mucho" is an adjective when accompanying nouns and as such it needs to agree with the noun.
For example:
Mucho dinero
A lot of money (dinero, singular masculine noun)
Mucha sal
A lot of salt (sal, singular feminine noun)
Muchos hombres
Lots of men (hombres, plural masculine noun)
Muchas mujeres
Lots of women (mujeres, plural feminine noun)
Here is a lesson on Quantitative adjectives that will help you understand and practice:
Using demasiado, bastante, suficiente, poco, tanto, mucho
I hope this helps,
Saludos
Inma
