How do i make observations and calculate data involving metric units?

Define qualitative and quantitative observations.
Distinguish between qualitative and quantitative observations.
Use Quantitative observations in measurements.
State the different measurement systems used in chemistry.
State the different prefixes used in the metric system.
Do unit conversions.
Use scientific notation and significant figures.
Use basic calculations and dimensional analysis.
Use mathematical equations in chemistry.
(i hope this helps??)

The density of water is 1 g/cm cubed and in order for the pebble to sink its density has to be greater than the density of water and in order for the twig to float its density has to be less than the density of water