How would the appearance of a graph look if it had the mass of several samples of aluminum on the horizontal axis and the density of the aluminum on the vertical axis?

Answer 1

It should look like an approximate horizontal line as it is assumed that the samples of aluminium were all at the same temperature when their weight was measured - density is a function of the material (and its temperature and pressure), not how much of it you have and so regardless of the mass, the density should be a constant, but due to experimental error in measurements and rounding of calculations, the line may not be exactly a straight horizontal line.

If there is a point way off the line, there are three possibilities:

1) Measurement were inaccurate;

2) Calculation based on the measurement made was inaccurate

3) There is a difference in make up of the sample, eg it is hollow whereas the others are solid or it could contain impurities whereas the others are [near enough] pure.

Answer 2

The graph would be a series of points, along a horizontal line that intersected
the y-axis at 2.7 gm/Ml ... the density of aluminum.

Density depends only on the substance, and not on the size of the sample.

Answer 3

If the samples of aluminium are identical the density will be identical.
And the graph will be a parallel to the horizontal axis; this graph has any meaning.