问题
填空题
一种物质的质量与其体积的比值是一定的，物质不同，这个比值______，这反映了不同物质的不同性质，物理学中用______表示这种特性．
答案
同种物质，质量与体积的比值是一定的；不同物质，质量与体积的比值一般不同．由此可见，质量与体积的比值反映了不同物质的不同性质，物理学中用密度表示这种特性．
故答案为：不同；密度．
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一种物质的质量与其体积的比值是一定的，物质不同，这个比值______，这反映了不同物质的不同性质，物理学中用______表示这种特性．
同种物质，质量与体积的比值是一定的；不同物质，质量与体积的比值一般不同．由此可见，质量与体积的比值反映了不同物质的不同性质，物理学中用密度表示这种特性．
故答案为：不同；密度．
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| Mrs Jones was very fond of singing. She had a good voice, 1 some of her high notes sounded like a gate which someone had forgotten to 2 . Mrs Jones was very conscious (清楚的) of this 3 , and took every 4 she could find to 5 these high notes. As she lived in a small house, where she could not practise without 6 the rest of the family, she 7 went for a long walk along the country roads 8 she had time, and practiced her high notes there. Whenever she 9 a car or a person coming along the road, she stopped and 10 until she could no longer be heard 11 she started singing again. One afternoon, however, a fast open car came up behind her 12 and so fast that she didn't hear it until it was 13 a few meters from her. She was singing her highest and most difficult notes at the time, and as the car 14 her, she saw an 15 expression suddenly come over 16 driver's face. He put his brakes (刹车) on, and as soon as the car stopped, jumped out and began to 17 all his tyres (轮胎) carefully. Mrs Jones did not dare to tell him 18 the noise he had heard had really been, 19 he got back into his car and drove off as 20 as he had been when he stopped. | ||||
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