When a substance undergoes a phase change it still has a definite
a. mass.
b. shape.
c. volume.
d. temperature.

The correct answer is option d, that is, temperature.

Explanation:

The temperature of any substance is associated with its average kinetic energy, where energy signifies the tendency to perform certain functions. During the heating of a solid, the average kinetic energy of the substance enhances due to which there is an upsurge in temperature. However, at the time of phase change, the energy taken in or given is known as latent heat, that is, used only to produce bonds in between the molecules or to dissociate the bonds in between the molecules. This heat will not influence the average kinetic energy of the substance. As the average kinetic energy of the substance will stay similar at the time of phase change, the temperature will also stay similar.

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

b.

the accuracy of the data.