题目

下列各组物质的变化中，前者属于化学变化，后者属于物理变化的是（ ） A．冰雪融化，由空气制氧气   B．钢铁生锈，纸的燃烧 C．蜡烛燃烧，蜡烛融化   D．汽油挥发，食物腐烂 答案：【考点】化学变化和物理变化的判别． 【专题】物质的变化与性质． 【分析】化学变化过程中有新物质生成，物理变化过程中没有新物质生成，是否生成新物质是判断化学变化的依据． 【解答】解：A、冰雪融化过程中，只是水由固体变成液体，没有生成新物质，属于物理变化，由空气制氧气过程中没语法考察（每小题1分，共5分`）将下列句子的直接引语转换成间接引语，间接引语转换成直接引语 1.Nancy asked her deskmate, “How did you work out the problem, Bob?” Nancy asked Bob how he ______ _______out the problem. 2. “I found my wallet under the desk, ”Lucy said to her mom. Lucy ______ her mom that she had found_______ wallet under the desk. 3.The teacher told us not to make any noise then. The teacher said to us, “______ make any noise ______” 4. Mom asked me whether I had finished my homework. “You have finished your homework,______ ______ ?”mom asked me. 5.Rainy asked her father what they would have for supper. Rainy asked her father, “Dad! What ______ ______ have for supper?”