All matter has mass and volume., however the mass of different substances occupies different volumes.
For example: we notice that iron or concrete is heavy, while the same amount of rubber or plastic is light.
The property that allows us to measure the lightness or heaviness of a substance is called density. The greater the density of a body, the heavier it will appear to us.
Density is defined as the ratio between the mass of a body and the volume it occupies. Thus, as in the international system, mass is measured in kilograms (kg) and volume in cubic meters (m3) density will be measured in kilograms per cubic meter (kg/m3).
Most substances have densities similar to water, so if this unit were used, very large numbers would still be used. To avoid this, another unit of measurement is usually used, the gram per cubic centimeter (gr/cm3).
The density of a body is related to its buoyancy, one substance will float above another if its density is lower.
This is why wood floats on water and lead sinks in it, because lead has a higher density than water while wood has a lower density, but both substances will sink in gasoline , which has a lower density.
The density of water is 1 g/cm3this means that 1 liter of water is also equal to 1 kilogram of water.
Exercises resolved in density
Solved exercises 1
A piece of platinum metal with a density of 21.5 g/cm3 it has a volume of 4.49 cm3. What is its mass?
Using the density formula.
Values are cleared and replaced.
The mass is 96.5 grams.
Solved exercises 2
Calculate the density of mercury if 1.00 x 10of them grams occupy a volume of 7.36 cm3.
Using the density formula.
Substitute the mass and volume values in the formula to get the density.
The density is 13.6 g/cm3
Solved exercises 3
Calculate the volume of 65.0 g of liquid methanol (wood alcohol) if its density is 0.791 g/mL.
Using the density formula.
Clear v and replace the values.
The volume is 82.2ml.
Solved exercises 4
What is the mass in grams of a gold cube (density 19.32 g/cm3) if its length is 2.00 cm?
We can calculate the mass from the volume of the cube and its density.
The volume of a cube is its length cubed.
If we solve the density formula for the mass and substitute the volume and density of the cube, we get the mass.
The mass is 155 grams.
