Diameter tools
You use a graduated cylinder to measure the volume of the rock with the water and the water without the rock
Ruler
To determine the length of a rock, you can use a ruler or a tape measure. Simply place the rock on a flat surface, align the ruler next to it, and measure the distance from one end to the other in a straight line.
You could use a standard kitchen scale to measure out 10.5g of rock salt accurately. If you don't have a scale, you can estimate using measuring spoons, keeping in mind that 1 teaspoon of rock salt is approximately 6g.
We would use MassSingle!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
A metric ruler.
you would use mass
To calculate the volume of a rock, you can use the formula for the volume of a sphere (4/3 * pi * r^3) if the rock is spherical, or use the formula for the volume of a rectangular prism (length * width * height) if the rock has a more regular shape. Otherwise, you can measure the volume by water displacement: submerge the rock in water and measure the increase in water level to find its volume.
Grams
To measure the volume of irregularly shaped rocks, you can use the water displacement method. Submerge the rock in a container of water and measure the change in water volume as the rock displaces the water. The difference in water volume before and after submerging the rock will give you the volume of the rock.
We would use a ruler to measure the length of a rock. Then, when we were ready to write down the result of the measurement, or tell someone else about it, we would pick the best unit of length to use. The best one would be the unit that results in the most convenient number. For a tiny rock, the "millimeter" might be best. For a medium rock, the "centimeter" might be best. For a large rock, the "meter" might be best. A really humongous rock, such as the moon, might warrant the use of the "kilometer".
You use a triple-beam scale to measure mass.