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

How to make scientific observations?

Observe something through your senses or record information using scientific tools and instruments and ask questions about your scientific observations (e.g., natural phenomena).

How to calculate data involving metric units?

To convert from one unit to another within the metric system usually means moving a decimal point (e.g., 1000000mm = 100000cm = 10000dm = 1000m = 100dkm = 10hm = 1km).

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.