Density

Key Questions• What is density?• How is density measured?• How do you calculate density?

How close the atoms or molecules are to each other

More than “heaviness” - density includes how much space an object takes up!!

All substances have density including liquids, solids, and gases

Density is the measure of the “compactness” of a material

“Compactness”

Density

Density describes how much mass is in a given volume of a material.

Mass is amount of matter in an object (usually measured in grams)

Volume is the amount of space an object takes up (usually measured in ml or cm3)

We have a kilogram of feathers and a kilogram of steel…

which has more mass?Which has a larger volume?Which is more dense?

OR

Density EQUATION

Density = mass/volume or D= m/v

A solid wax candle has a volume of 1,700 mL.

The candle has a mass of 1.5 kg (1,500 g).

What is the density of the candle?

Calculating Density1. Looking for: …the density of the candle

2. Given: …mass = 1500 g; volume = 1700

mL3. Relationship: D = m/V

= .88 g/mL

Solving Problems

4. Solution: 1,500 g ÷ 1,700 mL = 0.8823529 g/mL

What do you think?

If the volume stays the same and the mass increases . . . the density will

If the mass stays the same and the volume increases . . . The density will

Lead floats on liquid mercury! Explain.

Density

• Solids, liquids and gases are matter, so they all have density.

• The density of water is about one gram per cubic centimeter.

Density

The units used for density depend on whether the substance is solid or liquid.

For liquids use units of grams per milliliter (g/mL)

For solids use density in units of g/cm3 or kg/m3.

Density

Density is a property of material independent of quantity or shape.

Density of common materials

Liquids tend to be less dense than solids of the same material.

Ex. solder

Density of common materials

• Water is an exception to this rule. • The density of solid water (ice) is less than the density of liquid water.

Density of common materials

Ice vs. water…..

Determining Density

To find the density of a material, you need to know the mass and volume of a solid sample of the material.1. Mass is measured with

a balance or scale.2. Use the displacement

method or calculate the volume.

DETERMINING DENSITY

Regular Shapes – mass, then determine the volume by formula

EX: cubes, cylinders, spheres, cones, etc. Irregular shapes – mass, then measure displacement of a liquid

(usually water) by that irregularly shaped object

1.Use a graduated cylinder2.Add water to a predetermined level - record.

3.Gently drop in the irregularly shaped object.

4.Read the graduated cylinder – record.

5.Subtract the first water level from the second – this is the volume

Density TableSINK or FLOATIn Water (D = 1.0 g/mL)Float

Float

Float

Sink

Sink

Sink

Float

Float

(alcohol)

(fuel)