WHAT IS DENSITYWHAT IS DENSITY

One of the most important physical One of the most important physical properties of a substance is its properties of a substance is its density, or what is mass per unit density, or what is mass per unit volume. The property of density may volume. The property of density may be used to help identify a substance. be used to help identify a substance. Gold, for example, is much more Gold, for example, is much more dense (heavier) a substance than dense (heavier) a substance than copper even though their colors may copper even though their colors may be similar.be similar.

Density is the mass in grams (g) for Density is the mass in grams (g) for each milliliter (mL) or cubic each milliliter (mL) or cubic centimeter (cm3) of a substance.centimeter (cm3) of a substance.

This relationship may be expressed This relationship may be expressed as follows: Density = Mass / Volume as follows: Density = Mass / Volume or or

D = M/VD = M/V

Question #1Question #1

What is the density of a solid whose What is the density of a solid whose mass is 19.57g and whose volume is mass is 19.57g and whose volume is 3.6mL?3.6mL?

AnswerAnswer

D = mass / volumeD = mass / volume D = 19.57g / 3.6mLD = 19.57g / 3.6mL D = 5.6g/mLD = 5.6g/mL

Question #2Question #2

An irregular solid has a mass of An irregular solid has a mass of 12.77 grams. When the solid is 12.77 grams. When the solid is lowered into a graduated cylinder lowered into a graduated cylinder filled with 10.0 mL of water, the filled with 10.0 mL of water, the water level rises to 13.1mL. What is water level rises to 13.1mL. What is the density of the solid?the density of the solid?

AnswerAnswer

Density = Mass / VolumeDensity = Mass / Volume Mass = 12.77gMass = 12.77g Volume = 13.1mL – 10.0mL = 3.1mLVolume = 13.1mL – 10.0mL = 3.1mL D = 12.77g / 3.1mLD = 12.77g / 3.1mL D = 4.12 g /mLD = 4.12 g /mL

Question #3Question #3

The method used in this experiment The method used in this experiment would not be a satisfactory way to would not be a satisfactory way to measure the volume of salt or sugar measure the volume of salt or sugar crystals. Why?crystals. Why?

Question #4Question #4

What has a greater mass? A pound of What has a greater mass? A pound of lead or a pound of feathers.lead or a pound of feathers.

What has a greater density? 100g of What has a greater density? 100g of lead or 100 g feathers.lead or 100 g feathers.

Density Comparison to WaterDensity Comparison to Water

In chemistry, the density of many In chemistry, the density of many substances is compared to the substances is compared to the density of water. Does an object density of water. Does an object float on water or sink in the water? If float on water or sink in the water? If an object such as a piece of wood an object such as a piece of wood floats on water it is less dense than floats on water it is less dense than water vs. if a rock sinks, it is more water vs. if a rock sinks, it is more dense than water.dense than water.

Densities of Common Elements and Densities of Common Elements and CompoundsCompounds

SubstanceSubstance Density (g/ml)Density (g/ml)

Pine woodPine wood 0.35 – 0.500.35 – 0.50

WaterWater 1.001.00

SaltSalt 2.162.16

Aluminum Aluminum 2.702.70

GoldGold 19.319.3

MercuryMercury 7.807.80

IronIron 13.513.5