September 29, 2014• Do-Now: Come in quietly and

take out your notebook. Write your HW into agenda and answer the follow question.

• Answer the following questions reviewing metric system

• WRITE THE METRIC UNIT FOR EACH QUANITY BELOW

• Kilograms• Seconds• Liters• Meters• Cubic centimeters

• HW

• Pages 74 and 75 in workbook

DensityDensityObjective: How is density

determined?

What is Density?What is Density?

• Which one is more dense, a bowling ball or a soccer ball?

• Even though they are both approximately the same size and shape, the bowling ball is much more dense.

DensityDensity

• Density is the amount of mass in a given a space

• Density = Mass Volume

• Hot Air• More energy, molecules are moving faster• Molecules are more spread apart• Which sample shows warmer air?

• Hot Air• More energy, molecules are moving faster• Molecules are more spread apart• Which sample shows warmer air?

The two rooms are the same size. 50 people come to one party and 37 people come to the other party. Which one is more dense

Let’s put it all together…Let’s put it all together…

• DENSITY is the ratio of the mass of a substance to the volume of the substance

UNITS: commonly expressed as grams per cubic centimeter for solids and liquids and grams per liter for

gases

Find the Density of the CubeFind the Density of the Cube

10 cm3 cm

8 cm

Mass = 480 grams

Volume= LxWxH=10x3038= 240 cm3

Density ProblemsDensity Problems

• Calculate the density of a rock that has a mass of 40 grams and a volume of 5 cm3.

• 40g/5 cm3 = 8 g/cm3

Density FactsDensity Facts

• The Density of a substance remains the same regardless of size, shape, or mass of sample!!!

• Example: The density of a piece of aluminum is 2.7 g/cm3.

• If you cut the Al bar in half, the density of each piece is still 2.7 g/cm3

• Even if you roll the aluminum into a sheet the density will still remain the same

Density of AluminumDensity of Aluminum

D = 2.7 g/cm3D = 2.7 g/cm3

By simply cutting the bar in half, the density remains the same!!!

What will change the density of an object?

What will change the density of an object?

• Temperature• As the temperature of a substance

INCREASES the density DECREASES due to the expansion of the substance

Inverse Relationship

Most substances EXPAND when heated and CONTRACT when cooled

• Warm air rises because it is LESS dense

• Cold air sinks because it is MORE dense

• Material DENSER than water will SINK in water

• Material LESS DENSE than water will FLOAT

• Materials with a density EQUAL TO water may remain at ANY LEVEL

• When several objects of different densities float on water, the LEAST DENSE objects float HIGHEST.

A B

C

D

Water: 1 g/ml

Object D: 2 g/cc

Object C: 1 g/cc

Object B: 0.4g/cc

Object A: 0.8g/ccWhy is object D sinking

Why is object A floating

How do we measure the MASS of an object?

How do we measure the VOLUME of a cube?