Answer
The cube will float in the seawater because the sea water is denser than it.
Work Step by Step
We determine the cube's volume:
$\text{Volume}=1.20^3=1.728\text{ cm}^3$
Convert mass to grams:
$\text{Mass}=1.70\times 10^{-3}=1.70\text{ g}$
We calculate the cube's density:
$\text{Density}=\frac{1.70\text{ g}}{1.728\text{ cm}^3}\approx 0.984\text{ g/cm}^3$
Yes, the HDPE cube will float because its density ($0.984\text{ g/cm}^3$) is less than that of seawater ($1.03\text{ g/cm}^3$).
