Which has more mass?

A) 1 kilogram of feathers

B) 1 kilogram of bricks

They are the same!

1 kg = 1 kg

Which takes up more space?

A) 1 kilogram of feathers

B) 1 kilogram of bricks

The Feathers

Measure matter by finding the density!

Which has the greater density?

A) steel paper clip

B) steel bar

The density of steel is the same! Size doesn’t matter!

Density of Steel

steel bar

Units for Density

Metric Units:

Solid: g/cm3

Liquid: g/mL

Density of water is 1g/mL (at 4º C)

Memorize This!

• Density of Water: 1.00 g/mL

• Density of Ice: 0.92 g/mL

Which one floats? Why?

Which of the following will float on water?Why is it good to know the density?

All those lessthan 1.0 g/mL

Density helps you identify a substance

Predict the correct “floating order” of the substances as they would appear in the “Density Column”.

Substance Density g/cm3

Copper 8.8

Corn oil 0.925

Corn syrup 1.38

Glycerin 1.26

Mercury 13.6

Plastic 0.93

Rubber 1.34

Tar 1.02

Water 1.00

Wood 0.7

Specific Gravity

Specific gravity is the same as the density except: There are no units! Why? Because they cancel!

Ex: Density of water: 1 g/cm3

Specific Gravity of water: 1 (no units!)

Specific Gravity =

Density of Substance (g/cm3)

Density of Water (g/cm3)

What is the specific gravity?It is the same as the density but it has no units!

Calculating Density• Obtain mass using a balance.

• Obtain volume by any of these methods.– Ruler: Volume = L x W x H– Graduated cylinder– Water displacement

d

m

v“Magic Circles”

d = m/vm = d x vv = m/d

1) Is the bar really gold or fool’s gold?Find the density of the bar if the mass is 1891.4 g and the dimensions are 3.50 cm by 3.50 cm by 8.00 cm.

• Gold has a density of 19.3 g/cm3

V = L x W x H

D = M/V

1891.4 g / 98.0 cm3

= 19.3 g/cm3 Yes it’s gold! d

m

v

What is theSpecific Gravity?

D = M/V

16.98 g / 21.50 mL

= 0.7900 g/mL It is alcohol!

2) Is this liquid water, alcohol, or kerosene?

Find the density of the liquid if the mass is 16.98 g? Water 1.0 g/mLAlcohol 0.79 g/mLKerosene 0.82 g/mL

• Read the volume

d

m

v

What is theSpecific Gravity?

3) Is the “Silver Surfer” really made of silver? We obtained a sample with a mass of 262.5 g. Platinum 21.5 g/cm3

Silver 10.5 g/cm3

Tin 7.3 g/cm3

Find the volume by water displacement.

d

m

v

d = m/v

= 262.5 g / 25.0 cm3

= 10.5 g/cm3 It is Silver!

4) What is the volume in mL of this syrup if it has a density of 0.630 g/mL and a mass of 78.00 g?

v = m/d= 78.00g ÷ 0.630 g/mL= 124 mL

d

m

v

5) What is the mass in grams of this lead pipe if it has a density of 11.4 g/cm3 and a volume of 55.0 cc?

m = d x v= 11.4 g/cm3 x 55.0 cc= 627 g

d

m

v