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Density 3.4

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Density

If you think that these lily pads float because they are lightweight, you are only partially correct. The ratio of the mass of an object to its volume can be used to determine whether an object floats or sinks in water.

3.4

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Density >

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Determining Density

Determining Density

What determines the density of a substance?

Density is an intensive property that depends only on the composition (the stuff it is made of) of a substance, not on the size of the sample.

3.4

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Density > Determining Density

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

3.4

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Density > Determining Density

Each of these 10-g samples has a different volume because the densities vary.

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Density > Determining Density

Sample Densities

3.4

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Density > 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.

Water has a density of 1 g/cm3. If a substance is less dense than water, it floats. If a substance is more dense than water, it sinks.

3.4

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Density >

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Density and Temperature

Density and Temperature

How does a change in temperature affect

density? 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. This is because the molecules move farther apart.

3.4

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SAMPLE PROBLEM

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3.10

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SAMPLE PROBLEM

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What is the most dense substance in the picture?

Why does the oil float on top of the water?

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Practice Problems for Sample Problem 3.10

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SAMPLE PROBLEM

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3.11

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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

a. 0.737 g/mL.

b. 0.727 g/mL.

c. 1.36 g/mL.

d. 1.37 g/mL.

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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.

a. 0.500 cm3

b. 2.00 cm3

c. 38.6 cm3

d. 745 cm3

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3.4 Section Quiz

3. As the temperature increases, the density of most substances

a. increases.

b. decreases.

c. remains the same.

d. increases at first and then decreases.

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