What is a substance so pure it cannot be broken down? * Element
Compound
Mixture
Atom

Element

Explanation:

This is a pure substance which can't be split into simpler substances by chemical means

your answer would be a. 12.5 kg

a  solution  is always transparent, light passes through with no scattering from solute particles which are molecule in size. the  solution  is homogeneous and does not settle out. a colloid is intermediate between asolution  and a  suspension. while asuspension  will separate out a colloid will not.