DENSITYDENSITY

Let’s understand it once and Let’s understand it once and for all!for all!

MassMass Density = ------------Density = ------------ VolumeVolume

OROR mm D = -----D = ----- vv

TO CALCULATETO CALCULATE

THE TRIANGLE TRICKTHE TRIANGLE TRICK

m

D v

On your paper, draw the triangle and write the three formulas you can derive from this triangle.

UNITSUNITS

For mass, units may be grams, For mass, units may be grams, kilograms, centigrams, etc.kilograms, centigrams, etc.

For liquid volume, units may be For liquid volume, units may be liters, milliliters, kiloliters, etc.liters, milliliters, kiloliters, etc.

For solid volume, units may be cubic For solid volume, units may be cubic centimeters, cubic meters, etc.centimeters, cubic meters, etc.

DERIVED UNITSDERIVED UNITS The unit for density is a derived unit The unit for density is a derived unit

because it is a combination of two other because it is a combination of two other units. units.

Just as you divide the numbers to solve the Just as you divide the numbers to solve the problem, you also divide the units.problem, you also divide the units.

Ex. If mass is in g, and volume is in cmEx. If mass is in g, and volume is in cm33,, then the units for density will be:then the units for density will be: gg ---------- cmcm33

QUESTIONQUESTION

What would be some possible units What would be some possible units for the density of a liquid?for the density of a liquid?

LET’S DO SOME WORKLET’S DO SOME WORK

What is the density of 10 mL of a What is the density of 10 mL of a substance with a mass of 8 g?substance with a mass of 8 g?

mm 8 g 8 g g g

D = ---- D = ------- D = 0.8 D = ---- D = ------- D = 0.8 ---- ----

v 10 mL v 10 mL mLmL

MORE WORK TO DOMORE WORK TO DO

Now, we will figure the density of half Now, we will figure the density of half the amount of the same substance. the amount of the same substance.

– What is the mass? 4 gWhat is the mass? 4 g– What is the volume? 5 mLWhat is the volume? 5 mL

gg– -----------What is the density? 0.8 ----------------What is the density? 0.8 -----

mLmL SAME AS BEFORE!!! SAME AS BEFORE!!! WHY???WHY???

DENSITY IS A PHYSICAL DENSITY IS A PHYSICAL PROPERTYPROPERTY

Density does Density does NOTNOT depend on a substance’s depend on a substance’s shape or size. shape or size.

Density for a substance does Density for a substance does NOTNOT change change whether the substance is in a big amount or whether the substance is in a big amount or a small amount.a small amount.

Density depends on a substance’s chemical Density depends on a substance’s chemical composition, pressure, and temperature. If composition, pressure, and temperature. If any of these things change, the density may any of these things change, the density may change.change.

TAKE WATER FOR EXAMPLETAKE WATER FOR EXAMPLE The chemical formula for water is HThe chemical formula for water is H22O.O.

gg Water has a density of 1.0 --- .Water has a density of 1.0 --- .

mLmL A single drop of water has that density.A single drop of water has that density.

A bathtub full of water also has that density.A bathtub full of water also has that density.

The mass increased, but so did the volume. The mass increased, but so did the volume.

The ratio of the two after dividing is the SAME.The ratio of the two after dividing is the SAME.

WILL IT FLOAT?WILL IT FLOAT?

If a substance has a density that is If a substance has a density that is less than the density of water, it will less than the density of water, it will float.float.

If it has a density that is more than If it has a density that is more than the density of water, it will sink (it is the density of water, it will sink (it is heavier). heavier).

Will the substance from our earlier Will the substance from our earlier work float in water?work float in water?

MORE WORKMORE WORKCalculate the volume of an object if you know Calculate the volume of an object if you know

that the object has a mass of 14 grams and that the object has a mass of 14 grams and the density is 12 g/mL. the density is 12 g/mL.

Calculate the mass of an object if you know Calculate the mass of an object if you know that the object has a density of 13 g/mL and that the object has a density of 13 g/mL and the volume is 5 mL. the volume is 5 mL.

Calculate the density of a liquid in a beaker. Calculate the density of a liquid in a beaker. The beaker has a mass of 15 grams when The beaker has a mass of 15 grams when empty. The beaker plus an unknown liquid empty. The beaker plus an unknown liquid has a mass of 43 grams. What is the density has a mass of 43 grams. What is the density of the liquid if its volume is 10 mL? of the liquid if its volume is 10 mL?

10 mL

20 mL

30 mL

40 mLMaterial

A

Material D

Material C

Material B

Liquid

Material

Density (g/ml)

Milk 1.02

Fingernail Polish Remover

0.78

Olive Oil 0.92

Citric Acid 1.66

Identify the materials in the density column to the right by using the data table to help you.