Final answer:
The density of the unknown substance with a mass of 20 grams and a volume of 5 cm3 is calculated as 4.00 g/cm3 when rounded to the nearest hundredths place.
Step-by-step explanation:
To determine the density of the unknown substance, we'll use the density formula, which is density = mass/volume. Here, the given mass is 20 grams and the volume is 5 cm3.
The density calculation would be as follows:
Density = Mass/Volume
Density = 20 g / 5 cm3
Density = 4 g/cm3.
Applying significant figures rule, and rounding off to the nearest hundredths place, we get the density to be 4.00 g/cm3 since the volume measurement has the least number of significant figures (three) and we maintain that in our final answer.