density

defining density

Density is an important physical property of matter. It reflects how closely packed the particles of matter are. When particles are packed together more tightly, matter has greater density. Differences in density of matter explain many phenomena, not just why helium balloons rise. For example, differences in density of cool and warm ocean water explain why currents such as the Gulf Stream flow through the oceans. Click image to the left or use the URL below. URL: To better understand density, think about a bowling ball and volleyball, pictured in the Figure 1.1. Imagine lifting each ball. The two balls are about the same size, but the bowling ball feels much heavier than the volleyball. Thats because the bowling ball is made of solid plastic, which contains a lot of tightly packed particles of matter. The volleyball, in contrast, is full of air, which contains fewer, more widely spaced particles of matter. In other words, the matter inside the bowling ball is denser than the matter inside the volleyball. Q: If you ever went bowling, you may have noticed that some bowling balls feel heavier than others even though they are the same size. How can this be? A: Bowling balls that feel lighter are made of matter that is less dense.

textbook_image

calculating density

The density of matter is actually the amount of matter in a given space. The amount of matter is measured by its mass, and the space matter takes up is measured by its volume. Therefore, the density of matter can be calculated with this formula: Density = mass volume Assume, for example, that a book has a mass of 500 g and a volume of 1000 cm3 . Then the density of the book is: Density = 500 g = 0.5 g/cm3 1000 cm3 Q: What is the density of a liquid that has a volume of 30 mL and a mass of 300 g? A: The density of the liquid is: Density = 300 g = 10 g/mL 30 mL

instructional diagrams

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questions

helium has greater density than air.

a. true

-->  b. false

density is a chemical property of matter.

a. true

-->  b. false

if two objects have the same density, they must have the same

a) mass.

b) volume.

c) weight.

-->  d) none of the above

if a 60-g object has a volume of 30 cm3, what is its density?

-->  a) 2 g/cm3

b) 0.5 cm3/g

c) 1800 g  cm3

d) none of the above

diagram questions

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