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To better understand density, think about a bowling ball and volleyball, pictured in the Figure below. Imagine lifting each ball. The two balls are about the size, but the bowling ball feels much than the volleyball. That’s because the bowling ball is made of , which contains a lot of particles of matter. The volleyball, in contrast, is full of , which contains fewer, more particles of matter. In other words, the matter inside the bowling ball is than the matter inside the volleyball.