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第一章 氧 分子和原子 一、选择题 1.下列说法正确的是( )。 A.空气是一种元素 D.空气是一种化合物 C.空气是几种化合物的混合物 D.空气是几种单质和几种化合物的混合物 2.下列现象中一定发生了化学变化的是( )。 A.氢气和氧气混合 B.氧气变成淡蓝色液体 C.长期放置在空气中的碳酸氢铵逐渐
Chapter 1 Oxygen Molecules and Atoms 1. Multiple Choice Questions 1. The following statement is correct (). A. The air is an element D. The air is a compound C. The air is a mixture of several compounds D. The air is a mixture of several simple substances and several compounds 2. The following phenomena must have chemical changes () . A. Hydrogen and oxygen are mixed B. Oxygen turns light blue liquid C. Ammonium bicarbonate that is placed in the air for a long time gradually