Apr 18, 2023 Physics 1 (Garcia) SJSU

Chapter 12 Solids

(Just the section on “Density”)

Part II: Properties of Matter

Apr 18, 2023 Physics 1 (Garcia) SJSU

Demo: Iron and Cork

What is heavier, iron or cork?

Depends on how much you have. A big bag of cork can weigh more than a small iron nail.

Think of iron as being heavier because it is heavier for the same volume.

Small iron nail

BIG BAGOF

CORK

Apr 18, 2023 Physics 1 (Garcia) SJSU

Density

Define density as mass per volume,

( Density ) =

Densities ( in grams per cubic centimeter ):

Gold: 19.3 Mercury: 13.6 Lead: 11.3

Iron: 7.9 Water: 1.0 Cork: 0.2

( Mass )

( Volume )

(See Table 12.1, page 232)Liquids

Apr 18, 2023 Physics 1 (Garcia) SJSU

Demo: Gold Brick

Compute density of gold brick.

Dimensions: (20.5 cm)x(10 cm)x(5 cm)

Volume: 1025 cubic centimeters (= 1.025 liters)

Mass: 11,600 grams (about 26 pounds)

Density = (11,600) / (1025) = 11.3 g/cm3

Check with table that this is density of…

Apr 18, 2023 Physics 1 (Garcia) SJSU

Demo: Fool’s Gold

Use displacement to find irregular volumes.

Pyrite (called Fool’s Gold) is an iron ore (FeS2).Pyrite sample has:Mass: 61 gVolume: 12 cm3

Density =( 61 ) / ( 12 ) = 5.1 g/cm3

About a quarter the density of real gold.

Apr 18, 2023 Physics 1 (Garcia) SJSU

Check Yourself

Water expands when it freezes into ice.Which has more volume, kilogram of ice or kg of water?

Which has more mass, a kg of ice or a kg of water?

Which has a higher density, water or ice (or the same)?

Which has more mass, a liter of ice or a liter of water?

Apr 18, 2023 Physics 1 (Garcia) SJSU

Density of Water

One liter of water (1000 cm3) has a mass of one kilogram (1000 grams) so density of water is 1.0 g/cm3.

Density of water varies slightly with temperature, becoming less dense as temperature rises. Warm water rises and cold water sinks.

Density of ice = 0.92 g/cm3

Density drops on freezing