Density

a physical property of matter

Property = a characteristic that gives a substance identity

Properties of Vinegar:

- clear liquid

- strong odor

- reacts with baking soda

- acidic

Physical Properties

can be observed without changing the composition of the substance

Examples;

-Color

-Texture

-Shape

-Hardness

-Buoyancy

-Viscosity

-Miscibility

-Density

DENSITYDENSITYStyrofoamStyrofoam BrickBrick

Brick is more dense than Styrofoam because there is

more mass

packed into the

same volume

(more molecules or atoms in the same space.)

Density

Density can be defined as “unit mass per unit volume”

Density = Mass / Volume

D = m / v

Example: DensityDensity is a property of matter. If you measure the mass and the volume of an object, you can calculate it’s density using the formula:

(g) (mL)

D = m/v

Density = mass/volumeSo, the units of density must be…. g/mL

The Units for density come from this formula…

• Why is density measured in g/mL?

Because the formula for density is

(aka “grams per milliliter”) (not “gee slash em-ell”)

m mass (in grams) g

D = ----- = ------------ -------------- ----

v volume (in milliliters) mL

Measurement

Metric System

s second Time

K or o C Kelvin or

degree celsiusTemperature

Lliter Volume

g gram Mass

m meterLength

Unit Symbol UnitQuantity

Volume is special

because:

• Volume can be measured in

liters (L),

milliliters (mL), etc. s

or…

OR…

• Volume can be measured in

cubic meters (m3)

centimeters (cm3),

…..etc.

Remember;

1 cm1 cm3 3 = 1 mL = 1 mL

Remember this geometry?• Volume of a cube is ….

l x w x hi.e. 4cm x 5cm x 2cm = 40 cm3

i.e. x (5cm)2 x 10cm = 250 cm3

•Volume of a cylinder is ….

r2 h

Determining the Volume of an Irregularly Shaped Solid

22 mL 32 mL

Units of Density:– Mass is measured in g.– Volume is measured in mL or cm3.– Density is mass / volume,

(g) / (mL) (g) / (cm3) ,so..

density is measured in:

g/mLor

g/cm3

1 cm1 cm3 3 = 1 mL = 1 mL

DENSITY - an important and useful physical property

Density mass (g)volume (cm3)

Density mass (g)volume (cm3)

13.6 g/cm13.6 g/cm33 21.5 g/cm21.5 g/cm33

Aluminum

2.7 g/cm2.7 g/cm33

PlatinumMercury

Density of Gold:

19.30 g/mL

Silver:

10.50 g/mL

Aluminum:  2.70 g/mL

Atoms of some elements are more dense Atoms of some elements are more dense than others. than others.

Substance Density (g/mL)

 • Air 0.0013 g/mL

• Wood (Oak) 0.80 g/mL

• Steel  7.80 g/mL

•Water  1.00 g/mL

Sample Problem

• What is the density of 5.0 g of tin that has a volume of 1.2 mL?

D = m / v

= 4.2 g/mL

D = ?

m = 5.0 g

v = 1.2 mL

Steps for Solving Problems

1. Write the shopping list:

• the unknown variable. (what’s the question asking for?)

• all of the known variables.

2. Write the formula you will be using.

3. Calculate the final answer and include the units.

Sample Problem

• What is the density of 45.0 g of a liquid that has a volume of 62.5 mL?

D = m / v

= g/mL

D = ?

m = 45.0 g

v = 62.5 mL

Variations of the Density Formula:

D = m/v

v = m/D

m = v • D

D v

m

Sample Problem

What is the volume of 21.0 g of tin? (Density of Tin = 4.2 g/mL)

v = ?

D = 4.2 g/mL

m = 21.0 g

v = m / D

v = 5 mL

Sample Problem

What is the mass of 20 cm3 of tin? (Density of Tin = 4.2 g/mL)

m = ?

D = 4.2 g/mL

v = 20 cm3

m = v D

m = 84 g = 4.2 g/cm3

= 20 mL

Review:

3 methods of measuring volume:

• directly using glassware

• geometry (e.g. l • w • h )• water displacement (vf – vi)

Variations of the Density Formula:

D = m/v

v = m/D

m = v • D

1. Write the unknown variable.

2.      Write all the known variables.

3.      Convert all variables to similar units.

4.      Write formula you will be using.

5.      Calculate: “Plug and Chug”

6.      Circle your final answer with correct units.