5. Which statement is always true about conservation of matter?
A. If a gas forms, the mass of a system decreases.
B. If a solid forms, the mass of a system increases.
C. The mass of a system does not change during a chemical
reaction.
D. The mass of a system changes when a substance changes from
liquid to gas, but it does not change in a chemical reaction.

C. The mass of a system does not change during a chemical

reaction.

Explanation:

mass doesn't just disappear, it can change form but it cant disappear

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."