granite density: 2.7 g/ml basalt density: 3.0 g/ml ice density: 0.9 g/ml water density: 1.0 g/ml

DENSITYGranite

Density: 2.7 g/mL

BasaltDensity: 3.0 g/mLIce

Density: 0.9 g/mLWater

Density: 1.0 g/mL

The Equation:

Density = mass/volume

Before we get into the equation as a whole, let’s consider the components:

mass and volume

What is mass?

Mass is the measure of matter within an object. Mass is different than weight. Weight takes into account gravity acting on the object.

So this means that you will weigh more on Earth than on the Moon, yet still have the same mass. This is because the Earth itself has more mass than the Moon, creating a stronger gravitational pull.

What is volume?

Volume is the amount of space an object takes up.

How do you find an object’s mass?

Place the object on an electronic balance

How do you find an object’s volume?

Mathematically (length x width x height)

Water displacement Volume can be expressed in

cm3 or mL 1 cm3 = 1 mL

Let’s look back at the equation:

Density = mass/volume

Density is simply the ratio of the amount of mass (matter) inside the space of an object

An Earth Science student is trying to determine the density of a sample of basalt she discovered in the field. The sample has a mass of 60 grams and a volume of 20 mL.

What is the density of the sample?

Density = mass/volumeSolution: ___________ g/mL

What if an object is cut in half? Does the density change?

A student has a wooden block that has a mass of 36 grams and a volume of 48 cm3. The density is 0.75 g/cm3

After cutting the block in half, the mass is now 18 grams, and the volume is 24 cm3. The density is 0.75 g/cm3

How can density change?

Density will decrease if you increase the volume of an object. Conversely, density will increase if you decrease the volume.

Air masses increase in volume when heated and this causes them to become less dense.

What do less dense objects tend to do?

Less dense objects will rise over more dense objects

Air that is less dense will rise, air that is more dense will sinkLess

Dense

More Dense

Things to know about density in Earth Science:

1. The Earth is layered based on density

2. Planets closest to the Sun are more dense than ones farther away

3. Warm air will expand and become less dense, then rise

More things to know about density in Earth Science:

4. Cool air will contract and become more dense, then sink5. Earth’s crust is made up of plates of varying densities. More dense plates plunge below less dense plates at convergent boundaries

Relevant Reference Tables for Density