Density is Rice University – All Rights Reserved© 2011 Equal Volume The amount of matter in a given space or volume, a relationship between mass and volume Greater DensityLess Density What is Density?

Mass is: Rice University – All Rights Reserved© 2011 Amount of matter in an object

Volume is: Rice University – All Rights Reserved© 2011 The amount of space an object takes up

Displacement A way to measure the volume of a solid by placing it in a known amount of liquid Rice University – All Rights Reserved© 2011 How can we measure the volume of an object?

Density tells us how heavy something is for its size. Density = MASS ÷ VOLUME An Elephant and a Mouse have the SAME DENSITY!

Let’s practice calculating density! 25 grams of salami 5 mL = density of 5g/mL 16 grams of cheese 8 cubic cm. = density of 2g/cm3 Salami is more dense than Cheese!

Each cube is the same size, but has different weight and densities because of what they are made of! We can use DENSITY to identify one element from another.

One of these is not gold... Fool’s Gold density = 4.8 Real Gold density = 19.3

Often times in chemistry, the density of a substance is compared to the density of water (1.0 g/ml). Objects that float on water have density values less than 1 (g/ml or g/cm3) Objects that sink in water have density values greater than 1 (g/ml or g/cm3)

Water as a Standard 1 g of water has a volume of 1 ml and also 1 cm 3 Rice University – All Rights Reserved© 2011

We can also compare density without calculating it: Dense matter sinks in water, while less dense floats above it! water motor oil cooking oil

Hydrogen and Helium are less dense than Oxygen, so they float! Carbon dioxide (our breath) is more dense than Oxygen, so it sinks! CO2 H He It is the same for gases: