The graph shows the heating curve of a chemical substance as it undergoes state changes from solid to liquid to gas. analyze the curve, and answer the questions
the substance is entirely solid between positions
b and c
particles of the substance are in the liquid state and are gaining kinetic energy between positions
reset
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Particles of the substance are in liquid state will gain kinetic energy between positions C and D.

Explanation:

Problem it tells us that between B an C the substance is solid, but I would say that is solid between A and B while between B and C it is a melting process in which particles will gain energy to transform from solid to liquid.

Now between C and D the particles of the liquid will receive energy which is transformed in kinetic energy so the participles will move faster.

Between D and E the particles the energy received is spent by the particles to pass from liquid state to vapors state.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

"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."