Determining Density

3.4 Determining Density • Density is the ratio of the mass of an object to its volume.

3.4 Determining Density • Density is an intensive property that depends only on the composition of a substance, not on the size of the sample.

So, the density for a given substance defines the relationship between mass and volume • Like any relationship, it gives you 2 conversion factors • For gold, • 19.3 g/cm3 and 1 cm3/19.3 g

3.4 Determining Density • The density of corn oil is less than the density of corn syrup. For that reason, the oil floats on top of the syrup.

46 • A student finds a shiny piece of metal that she thinks is aluminum. In the lab, she determines the metal has a volume of 245 cm3 and a mass of 612 g. Is this metal aluminum?

Well, we can find the density of the material and compare it to the density in the table for aluminum and see if they match. • 612 g = 2.50 g • 245 cm3 cm3 • From the table, the density of aluminum is 2.70 g/cm3, so no the metal is not pure aluminum

3.4 Density and Temperature • Experiments show that the volume of most substances increases as the temperature increases. Meanwhile, the mass remains the same. Thus, the density must change. • The density of a substance generally decreases as its temperature increases.

for Sample Problem 3.10 Problem Solving 3.47 Solve Problem 47 with the help of an interactive guided tutorial.

3.11

for Sample Problem 3.11 Problem Solving 3.48 Solve Problem 48 with the help of an interactive guided tutorial.

3.4 Section Quiz • 1. If 50.0 mL of corn syrup have a mass of 68.7 g, the density of the corn syrup is • 0.737 g/mL. • 0.727 g/mL. • 1.36 g/mL. • 1.37 g/mL.

3.4 Section Quiz • 2. What is the volume of a pure gold coin that has a mass of 38.6 g? The density of gold is 19.3 g/cm3. • 0.500 cm3 • 2.00 cm3 • 38.6 cm3 • 745 cm3

3.4 Section Quiz • 3. As the temperature increases, the density of most substances • increases. • decreases. • remains the same. • increases at first and then decreases.

Determining Density