初三下学期冲刺中考系列讲义(第五讲)
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冲刺中考讲座课件为了帮助学生有效提高中考成绩,提升应对能力和自信心,学校特邀请了全市知名的名师来为同学们做中考冲刺讲座。
下面是本次讲座的课件内容,希望能对学生们有所帮助。
一、总体考试策略1. 把握做题时间,抢占先机- 建议考试前先简单算一下每道题的可用时间,并且尽可能快地完成每道题目。
- 建议尽快完成卷子上的选择题和填空题,不要在复杂的步骤上花太多时间,如果有疑问,可以先放一放,稍后再回过头来看看。
- 建议先解答熟悉的题目,这样可以提高答题速度和自信心,缓解一下紧张情绪。
2. 细节决定成败,一定要认真审题- 建议在做数学题的时候,认真审题,理顺思路,这样就可以避免走弯路,减少不必要的错误。
- 建议在做语文的填空题和阅读理解时,认真理解每个选项的含义,避免因小失大,造成误解。
- 建议在做英语作文,特别是翻译时,读完后先理解、然后再思考翻译方法及遣词造句,一定要将原文中的信息准确地表达出来。
3. 作文要点的把握- 建议认真阅读作文题目,理解题意并精准把握作文要点,避免偏离主题或划题思路错误。
- 建议多从日常生活中汲取素材、注意细节修辞和衔接方式,这些都是提升作文分数的关键。
- 建议尽可能多地练习作文,结合老师的评分标准和意见,提高自己对自身作文优缺点的把握程度。
二、语文篇章阅读策略1. 充分把握篇章结构- 建议读文章之前,先简单浏览一下文章标题以及某些词汇,了解文章内容,对于作者、时空背景也可以做了解,有利于全面把握文章的内在意义和主题。
- 建议逐一梳理各个段落的构建,注意段落之间的衔接和过渡,掌握文章的脉络和发展趋势。
2. 掌握主旨句- 建议在阅读文章之前,先看看文章的第一句话和最后一句话,结合标题大概了解文章主题。
- 建议逐一读取各个段落的第一句话,这些句子往往就是段落的主旨句,所以理解这些句子对于理解文章就有很大的帮助。
- 建议读取完文章后,回顾一下文章标题,进一步感受整篇文章的主题,结合标题理解文章内涵。
2019年重庆数学中考填空、选择难点题专题复习讲座五——方程组解决实际问题知识点一:多元方程组问题例1、某文具商店对文具进行组合销售,甲种组合:2支红色圆珠笔,4支黑色圆珠笔;乙种组合:3支红色圆珠笔,8支黑色圆珠笔,1个笔记本;丙种组合:2支红色圆珠笔,6支黑色圆珠笔,1个笔记本.已知红色圆珠笔每支2元,黑色圆珠笔每支1.5元,笔记本每个10元.某个周末销售这三种组合文具共485元,其中红色圆珠笔的销售额为116元,则笔记本的销售额为________元.150【分析】设卖出的甲,乙,丙种组合分别为x,y,z套,根据题意可列方程组经过化简消元可得y+z=15,因为甲种组合没有笔记本,乙种组合笔记本为1本, 丙种组合笔记本为1本,所以笔记本为1本的数量为y+z本,由“总价=单价×数量”可求出笔记本的销售额.【详解】解:设该天卖出的甲,乙,丙种组合分别为x,y,z套,根据题意列方程组方程组变形为由②-①消去x可得13(y+z)=195 ③③化简得:y+z=15甲种组合没有笔记本,乙种组合笔记本为1本, 丙种组合笔记本为1本,所以笔记本为1本的数量为:y+z=15(本)笔记本的销售额为(元)故答案为:150.【点睛】考查三元一次方程组的应用,整理方程消去未知数是解题的关键.巩固练习:1、某水果销售高在年末准备购进一批水果进行销售,经过市场调查发现芒果、车厘子、奇异果、火龙果比较受顾客的喜爱,于是制定了进货方案。
其中芒果、车厘子的进货量与奇异果、火龙果的进货量分别相同。
而芒果、车厘子的单价与火龙果。
奇异果的单价分别相同,已知芒果和车厘子的单价和为每千克180元,且芒果和车厘子的进货总价比奇异果和火龙果的进货总价多863 元。
由于年末资金周转不开,所以临时决定只购进芒果和车厘子,芒果和车厘子的进货量与原方案相同。
且进货量总数不超过300kg,则该水果商最多需要准备27431.5元进货资金。
2、某厂家以A、B两种原料,利用不同的工艺手法生产出了甲、乙、丙三种袋装产品,其中,甲产品每袋含1千克A原料、3千克B原料;乙产品每袋含2千克A原料、1千克B 原料;丙产品每袋含有1千克A原料、1千克B原料。
2022年中考几何模型一、角平分线模型知识精讲1. 过角平分线上一点向角的两边作垂线段,利用角平分线上的点到角两边的距离相等的性质来解决问题2. 若题目中已经有了角平分线和角平分线上一点到一边的垂线段(距离),则作另一边的垂线段,例:已知:AD是的平分线,,过点D于点E,则.3. 在角的两边上取相等的线段,结合角平分线构造全等三角形(角边等,造全等),已知:点D是平分线上的一点,在OA、OB上分别取点E、F,且,连接DE、DF4. 过角平分线上一点作角的一边的平行线,构造等腰三角形,例:已知:点D是平分线上的一点,过点D作三角形,即.5. 有角平分线时,过角一边上的点作角平分线的平行线,交角的另一边所在直线于一点,也可构造等腰三角形,例:已知:OC平分,点D是OA上一点,过点D作交OB的反向延长线于点E,则.6. 从角的一边上的一点作角平分线的垂线,使之与角的另一边相交,则可得到一个等腰三角形,例:已知:OE平分∠AOB,点D在OA上,DE⊥OE,则可延长DE交OB于点F,则DE=EF,OD=OF,∠ODF=∠OFD.7. 有角平分线时,可将等角放到直角三角形中,构造相似三角形,也可以另加一对相等的角构造相似三角形,例:4321DA4231EFCB(1)已知:OC 平分,点E 、F 分别在OA 、OB 上,过点E M ,过点F N(2)已知:OC 平分,点E 、F 在OC 上,于点M ,于点N ,则(3)已知:OC 平分,点E 、F 在OC ,8. 利用“在同圆或等圆中,相等的圆周角(圆心角)所对的弦相等”可得相等线段,例:已知:∠BAC 是圆O 的圆周角,∠DOE 是圆O 的圆心角,AF 平分∠BAC ,OG 平分∠DOE ,连接BF 、CF 、DG 、EG ,则BF =CF ,DG =EG .9. 【内内模型】如图,两个内角平分线交于点D ,则.10. 【内外模型】如图,的一个内角平分线和一个外角平分线交于点D ,则.11. 【外外模型】如图,交于点D ,则.二、中点模型知识精讲1. 在等腰三角形中有底边中点或证明底边中点时,可以作底边的中线,利用等腰三角形的“三线合一”性质来解决问题.例:已知:在△ABC中,AB=AC,取BC的中点D,连接AD,则AD平分∠BAC,AD是边BC上的高,AD是BC边上的中线.【说明】应用等腰三角形“三线合一”的性质是证明两条直线垂直的重要方法.2. 在直角三角形中,有斜边中点或有斜边的倍分关系线段时,可以作斜边的中线解决问题,例:(1)如图,在Rt△ABC中,D为斜边AB的中点,连接CD,则CD=AD=BD.(2)如图,在Rt△ABC中,AB=2BC,作斜边AB上的中线CD,则AD=BD=CD=BC,△BCD是等边三角形.【总结】在直角三角形中,若遇到斜边的中点,则连接直角顶点与斜边的中点是解决问题的基本方法,作这条辅助线的目的是得到三条相等的线段及两对相等的角. 3. 将三角形的中线延长一倍,构造全等三角形或平行四边形(倍长中线),例:(1)如图,在△ABC中,AD为△ABC的中线,延长AD至点E,使得DE=AD,连接BE,则△ADC≌△EDB.(2)如图,在△ABC中,AD为△ABC的中线,延长AD至点E,使得DE=AD,连接BE,则四边形ABEC是平行四边形.4. 将三角形中线上的一部分延长一倍,构造全等三角形或平行四边形,例:如图,已知点E是△AD上的一点,延长AD至点F,使得DE=DF,连接BF、CF,则四边形BFCE为平行四边形或△BDF≌△CDE或△BED≌△CFD.【总结】证明两条线段相等常用的方法:①当要证明的两条线段是两个三角形的边时,一般通过证明这两条线段所在的两个三角形全等,通过三角形全等的对应边相等来证明两条线段相等;②当两条线段是同一个三角形的两条边时,一般证明这两条边所对的角相等,利用等角对等边证明两条线段相等.5. 有以线段中点为端点的线段时,可以倍长此线段,构造全等三角形或平行四边形,例:如图,已知点C边AE上一点,O为AB的中点,延长CO至点D,使得,连接AD、BD,四边形ADBC为平行四边形.6. 有三角形中线时,可过中点所在的边的两端点向中线作垂线,构造全等三角形,例:如图,AF为△ABC的中线,作BD⊥AF交AF延长线于点D,作CE⊥AF于点E,则△BDN≌△CEN.7. 在三角形中,有一边的中点时,过中点作三角形一边的平行线或把某条线段构造成中位线,利用已知的条件可求线段长,例:如图,D为AB的中点,过点D作DE∥BC,则DE为△ABC的中位线;过点B作BF∥DC 交AC的延长线于点F,则DC为△ABF的中位线.8. 有两个(或两个以上)中点时,连接任意两个中点可得三角形的中位线,例:如图,D、E、F分别为△ABC三边中点,连接DE、DF、EF,则.9. 有一边中点,并且在已知或求证中涉及线段的倍分关系时,可以取另一边的中点,构造三角形的中位线,例:如图,点E是△ABC边BC的中点,取AC的中点F,连接EF,则EF∥AB,10. 当圆心与弧(或弦)的中点,可以利用垂径定理解决问题,例:(1)如图,,连接AC、OB,则OB⊥AC,OB平分AC.(2)如图,点C为弦AB的中点,连接OC,则OC⊥AB.三、平行模型知识精讲在一些有平行线却没有截线的问题中,通常需要添加辅助线构造“三线八角”,再运用平行线的有关知识解题,常见的辅助线添加方式如下:如果遇到两条平行线之间夹折线,一般应过折点作出与已知平行线平行的直线.1. 如图,已知AB∥CD,点E为AB、CD间的一点,过点E作EF∥AB,则∠A+∠C=∠AEC.2. 如图,已知AB∥CD,则∠A+∠AEC+∠C=360°.3. 如图,AB∥CD,则∠B=∠D+∠E.4. 如图,AB∥CD,则∠BEG+∠D+∠F=180°.5. 如图,AB∥CD,则∠ABE=∠D+∠E.四、垂直模型1. 在三角形中,若题目中已经有一边的高了,常作另一边上的高,然后用同角的余角相等证明角相等.例:如图,在△ABC中,AD⊥BC于点D,过点B作BE⊥AC交AC于点E,交AD于点F,则∠CBE=∠CAD,∠AFE=∠C=∠BFD.除了能得到角度间的关系外,还可以通过构造相似三角形来证明线段成比例或者用于求线段的长度.2. 在四边形中,如果有高线,可以再作垂线,构造特殊的四边形或者直角三角形.例:如图,在四边形ABCD中,AB⊥BC,DC⊥BC,过点D作DE⊥BC,垂足为点E,则四边形BCDE为矩形,△ADE为直角三角形.3. 在直角三角形中,常作斜边上的高,利用同角(等角)的余角相等,可得到相似三角形.例:如图,在Rt△ABC中,∠ACB=90°,过点C作CD⊥AB于点D,则∠A=∠DCB,∠B=∠ACD,△ABC∽△CBD∽△ACD.4. 若题中已有直线的垂线时,可再作已知直线的垂线,得到两条平行线.例:如图,在△ABC中,AF⊥BC于点F,过AB上一点D作DE⊥BC于点E,则DE∥AF,∠BDE=∠BAF,∠ADE+∠BAF=180°,△BDE∽△BAF.5. 若存在过一条直线上两点同时向另一条直线作垂线,可以再作一条垂线,构造一组平行线,利用平行线等分线段定理解决问题.6. 当两条互相垂直的弦的交点恰好在圆上,构成90°的圆周角,可构造直径.例:如图,点A在圆O上,∠BAC=90°,连接BC,则BC就是圆O的直径.7. 当圆中有互相垂直的弦时,经常作直径所对的圆周角,可以得到垂直于同一条直线的两条直线,利用平行弦所夹的弧相等来解决问题.例:在圆O中,弦AB⊥CD于点E,连接CO并延长交圆O于点F,连接DF,则FD⊥CD,FD∥AB,.8. 当圆中有和弦垂直的线段时,作直径所对的圆周角,可以得到直角三角形,通过相似三角形来解决问题.例:如图,△ABC内接于圆O,CD⊥AB于点D,连接CO并延长交圆O于点E,连接AE,则△ACE∽△DCB.五、对角互补模型知识精讲1. 全等型—90º如图,已知∠AOB=∠DCE=90º,OC平分∠AOB.则可以得到如下几个结论:①CD=CE,②OD+OE=OC,③2. 如图,已知∠DCE的一边与AO的延长线交于点D,∠AOB=∠DCE=90º,OC 平分∠AOB.则可得到如下几个结论:①CD=CE,②OE-OD=OC,③.3. 全等型—60º和120º如图,已知∠AOB=2∠DCE=120º,OC平分∠AOB.则可得到如下几个结论:①CD=CE,②OD+OE=OC,③.4. 全等型—和如图,已知∠AOB=,∠DCE=,OC平分∠AOB.则可以得到以下结论:①CD=CE,②OD+OE=2OC·cos,③.5. 相似型—90º如图,已知∠AOB=∠DCE=90º,∠BOC=.结论:CE=CD·.六、半角模型知识精讲1. 如图,在正方形ABCD中,E、F分别是BC、CD上的点,且∠EAF=45º,则BE+DF=EF.2. 如图,在正方形ABCD中,E、F分别是BC、CD上的点,且∠EAF=45º,则AE平分∠BEF,AF平分∠DFE.3. 如图,在正方形ABCD中,E、F分别是BC、CD上的点,且∠EAF=45º,则4. 如图,在正方形ABCD中,E、F分别是BC、CD上的点,且∠EAF=45º,过点A作AH⊥EF交EF于点H,则AH=AB.简证:由上述结论可知AE平分∠BEF,又∵AB⊥BC,∴AH=AB.5. 如图,在正方形ABCD中,E、F分别是BC、CD上的点,且∠EAF=45º,. 简证:由结论1可得EF=BE+DF,CE+CF+EF=CE+CF+BE+DF=2AB.6. 如图,在正方形ABCD中,E、F分别是BC、CD上的点,且∠EAF=45º,AE、AF分别与BD相交于点M、N,则.简证:如图,将△AND绕点A顺时针旋90º得到△AGB,连接GM.通过证明△AMG≌△AMN得MN=MG,DN=BG,∠GBE=90º,即可证.7. 如图,在正方形ABCD中,E、F分别是BC、CD上的点,且∠EAF=45º,AE、AF分别与BD相交于点M、N,则△BME△DFN△AMN△BAN△DMA△AFE.简证:通过证明角相等得到三角形相似,要善于使用上述结论.8. 如图,在正方形ABCD中,E、F分别是BC、CD上的点,且∠EAF=45º,AE、AF分别与BD相交于点M、N,则简证:连接AC,∵∠DAF=∠EAC,∠ADB=∠ACB,∴△ECA△NDA,又∵△AMN△AFE,∴.【补充】通过面积比是相似比的平方比亦可得到9. 如图,在正方形ABCD中,E、F分别是BC、CD上的点,且∠EAF=45º,AE、AF分别与BD相交于点M、N,则.简证:由结论7可得△DAM△BNA,∴,即.10. 如图,在正方形ABCD中,E、F分别是BC、CD上的点,且∠EAF=45º,AE、AF分别与BD相交于点M、N,则.简证:设,在Rt△CEF中,,化简得,.11. 如图,在正方形ABCD中,E、F分别是BC、CD上的点,且∠EAF=45º,AE、AF分别与BD相交于点M、N,则当BE=DF时,EF.证明:如图,作△AEF的外接圆,点P为EF的中点,连接OA、OE、OF、PC,过点A作AH⊥EF.∵∠EAF=45º,∴∠EOF=90º,设,则,∴当点A、O、P、C四点共线时,即BE=DF,、EF大值.12. 如图,在正方形ABCD中,E、F分别是BC、CD上的点,且∠EAF=45º,AE、AF分别与BD相交于点M、N简证:由结论8可得△△ECA△NDA,同理可得补充:等腰直角三角形与“半角模型”如图所示,在等腰直角三角形ABC中,若∠DCE=45º,则.证明:如图,将△ACD绕着点C顺时针旋转90º得到△,连接.∵旋转,∴△ACD≌△,∴AD=,在△DCE与△中,ED=,∵∠BE=∠BC+∠EBC=∠DAC+∠EBC=90º,∴,.七、倍半角模型知识精讲一、二倍角模型处理方法1. 作二倍角的平分线,构成等腰三角形.例:如图,在△ABC中,∠ABC=2∠C,作∠ABC的平分线交AC于点D,则∠DBC=∠C,DB=DC,即△DBC是等腰三角形.2. 延长二倍角的一边,使其等于二倍角的另一边,构成两个等腰三角形.例:如图,在△ABC中,∠B=2∠C,延长CB到点D,使得BD=AB,连接AD,则△ABD、△ADC都是等腰三角形.二、倍半角综合1. 由“倍”造“半”已知倍角求半角,将倍角所在的直角三角形相应的直角边顺势延长即可.如图,若,则()2. 由“半”造“倍”已知半角求倍角,将半角所在的直角三角形相应的直角边截取线段即可.如图,在Rt△ABC(∠A<45º)的直角边AC上取点D,当BD=AD时,则∠BDC=2∠A,设,则,在Rt△BCD中,由勾股定理可得,解得,故有.三、一些特殊的角度1. 由特殊角30º求tan15º的值如图,先构造一个含有30º角的直角三角形,设BC=1,,AB=2,再延长CA至D,使得AD=AB=2,连接BD,构造等腰△ABD,则∠D=∠BAC=15º,.2. 由特殊角45º求tan22.5º的值由图可得,.3. “345”三角形(1)如图1,Rt△ABC三边比为3:4:5,Rt△BCD三边比为,,;(2)如图2,Rt△ABC三边比为3:4:5,Rt△BCD三边比为,,;(3)如图3,Rt△ABC三边比为3:4:5,Rt△BCD三边比为,,.八、全等模型知识精讲一、几何变换中的全等模型1. 平移全等模型,如下图:2. 对称(翻折)全等模型,如下图:3. 旋转全等模型,如下图:二、一线三等角全等模型4. 三垂直全等模型,如图:5. 一线三直角全等模型,如图:6. 一线三等角与一组对应边相等全等模型,如图:三、手拉手全等模型7. 等腰三角形中的手拉手全等模型如图,△ABC与△ADE均为等腰三角形,且∠BAC=∠DAE,连接BD、CE,则△ABD ≌△ACE.8. 等边三角形中的手拉手全等模型如图,△ABC与△CDE均为等边三角形,点B、C、E三点共线,连接AE、BD,则△BCD≌△ACE.9. 一般三角形中的手拉手全等模型如图,在任意△ABC中,以AB为边作等边△ADB,以AC为边作等边△ACE,连接DC、BE,则△ADC≌△ACE.10. 正方形中的手拉手全等模型如图,在任意△ABC中,以AB为边作正方形ABDE,以AC为边作正方形ACFG,连接EC、BG,则△AEC≌△ABG.九、相似模型知识精讲1. A字型与反A字型相似2. 8字型与反8字型相似3. 蝴蝶型相似4. 共角共边相似模型5. 一线三等角6. 旋转相似模型拓展讲解:1. 射影定理(1)双垂直,如图:结论①△ABD∽△ACB,AB2=AD·AC;②△ADC∽△ACB,AC2=AD·AB;③△CDB∽△ACB,CB2=BD·BA.(2)斜射影相似结论:△ABD∽△ACB,AB2=AD·AC.2. 对角互补相似如图,在Rt△ABC中,∠C=90º,点O是AB的中点,若∠EOF=90º,则.证明:过点O作OD⊥AC于点D,OH⊥BC于点H,如图所示:通过△ODE∽△OHF即可得到3. 三平行相似如图,AB∥EF∥CD,若,则.证明:∵EF∥AB,∴△DEF∽△DAB,∴,即①同理△BEF∽△BCD,∴,即②①+②,得,.4. 内接矩形相似如图,四边形DEFG是△ABC的内接矩形,EF在BC边上,D、G分别在AB、AC边上,则△ADG∽△ABC,△ADN∽△ABM,△AGN∽△ACM,.十、倍长中线模型知识精讲1. 如图,在矩形ABCD中,若BD=BE,DF=EF,则AF⊥CF.2. 如图,四边形ABCD是平行四边形,BC=2AB,M为AD的中点,CE⊥AB于点E,则∠DME=3∠AEM.3. 如图,△ADE与△ABC均为等腰直角三角形,且EF=CF,求证(1)DF=BF;(2)DF⊥BF.4. 如图,△OAB∽△ODC,∠OAB=∠ODC=90º,BE=EC,求证:(1)AE=DE;(2)∠AED=2∠ABO.十一、弦图模型知识精讲1. 证法一以a、b为直角边(b>a),以c为斜边作四个全等的直角三角形,则每个直角三角形的面积等于2. 证法二以a、b为直角边(b>a),以c为斜边作四个全等的直角三角形,则每个直角三角形的面积等于3. 证法三以a、b为直角边,以c为斜边作两个全等的直角三角形,则每个直角三角形的面积等于4. 证法四如图所示,分别以a、b为直角边,以c为斜边的四个直角三角形全等,图中3个正方形的边长分别为a、b、c,整个图形的面积为S5. 证法五分别以a、b为直角边,以c为斜边的四个直角三角形全等,将它们按如图所示拼成一个多边形,并延长AC交DF于点P.。
Unit 5 Knowing about China语法:定语从句一.定语从句的概念在复合句中,修饰某一名词或代词的从句叫定语从句。
被修饰的名词或代词叫先行词,定语从句一般放在先行词的后面二. 定语从句的关系词及其用法定语从句起了形容词的作用,在句中修饰一个名词或代词。
被修饰的词叫做先行词,引导定语从句的词叫关系词,他的作用一是放在先行词与定语从句中间起了连接作用,二是在从句中担当一个成分,并与先行词保持数的一致。
1. Nearly all the streets are in straight lines, ________ from east to west. Those ________ run from north to south are called avenues.A. running; thatB. run; whoC. running; whoD. run; that2. This is the case ________ he’s had all his money stolen.A. whenB. whereC. thatD. on which3. Mr. Smith will pay a visit to Beijing this autumn, ________ we will enjoy the Olympic Games in 2008. A. where B. when C. which D. how4. The artist will not paint people or animals but he will paint anything ________ .A. that the little girl asks himB. the little girl asks him toC. for the little girl to ask himD. what the little girl asks him5. —How did you get in touch with the travel agent, Robin?—Oh, that’s easy. I surfed the Internet and then called one ________ the telephone number is provided.A. whichB. in whichC. of whichD. whose6. October 15 th is my birthday, ________ I will never forget.A. whenB. thatC. whatD. which7. The treatment will continue until the patient reaches the point ________ he can walk correctly and safely.A. whenB. whereC. whichD. whose8. There are several research centers in China _ _ _ a certain disease called Bird Flu is being studied.A. whichB. whereC. whenD. what9. I hope that the little ________ I have been able to do does good to them all.A. whichB. whatC. thatD. when10. The time is not far away ________ modern communications will becomewidespread in China’s vast countryside.A. asB. whenC. untilD. before11. ________ is known to everybody, Taiwan is a part of China. We must unify it.A. ItB. AsC. WhichD. What12. I shall never forget the day ________ Shen Zhou V was launched, ________ has a great effect on my life.A. when, whichB. that, whichC. which, thatD. when, that13. The bread my wife makes is much better than ________ you can buy at a store.A. that whichB. one thatC. that of whichD. this of which14. There is no such place ________ you dream of in all this world.A. thatB. whatC. whichD. as15. The people, ________ had been damaged by the flood, were given help by the Red Cross.A. all whose homesB. all of whose homesC. all their homesD. all of their homes16. The humans are destroying nature day by day, ________ of course, will cause severe punishment from it sooner or later.A. whoB. whenC. on whichD. which17. Is this research center ________ you visited the modern equipment last year?A. whereB. thatC. the one thatD. the one where18. Some pictures of the river brought the days back to the old ________ they swam in it.A. whenB. thatC. whoD. where19. The man showed us so heavy a stone ________ no man can lift.A. thatB. asC. whichD. and20. He stayed there for quite a long time, during ________ time he learned much spoken English.A. thatB. thisC. whichD. same答案与解析:1. A. 主语与run(延伸)是主动关系,所以用现在分词。
化学思想方法的应用第五讲物质的微粒观【题型特点】从微观的视角认识化学物质及其变化,是化学学科的重要特征。
“物质微粒观”作为一种重要的化学基本观念,它的形成对于学生理解和解释宏观的事实和现象, 理解化学反应的实质, 了解化学符号的意义等方面具有重要的意义。
特别是对于初中学生来说, 物质微粒观的建立, 是他们开启化学之门的基础。
“物质微粒观”其核心是微粒作用观,即不同层次的微粒本身是有结构的,微粒结构就是内部微粒间作用的结果;物质变化是微粒间的“强”相互作用代替“弱”相互作用。
物质微粒观的内容是丰富多彩的,它贯穿于整个中学化学学习过程中。
在初中阶段, 对物质微粒观的认识是以分子、原子概念的建立为标志的。
【主要考查内容】1.物质是由肉眼看不见的微粒构成的;2.微粒总是在不断运动的;3.微粒间有一定的间隔;4.微粒间存在着相互作用。
【必备知识梳理】1.微粒的基本性质:构成物质的微粒有以下性质:①微粒很小(质量小、体积小)②微粒时刻不停地做规则运动(运动速率与温度成正比)③微粒间有间隔(间隔与温度成正比,与压强成反比)④同种微粒,化学性质相同注意:①微粒时刻不停地做规则运动,温度高时运动速率快;温度低时运动速率慢,但不是不运动。
此观点可解释扩散现象。
②微粒间的间隔与温度成正比,温度高时微粒间的间隔变大,温度低时微粒间的间隔变小。
此观点可解释热胀冷缩现象。
③微粒本身的大小不受温度影响。
2.物质、元素、微粒之间的关系【典型例题】例1:1. (2017•成都)下列客观事实对应的微观解释不正确的是(A选项客观事实微观解释A 电解水得到氢气水中有氢分子B 闻到浓氨水的特殊气味分子在不停运动C 一滴水中有1.67×1021个水分子分子的体积很小D 金刚石和石墨的硬度不同碳原子排列方式不同【解析】水由水分子构成,水分子由氧原子和氢原子构成,水中只有氢元素和氧元素,A错误。
【答案】A例2:(2017∙长沙)2016 年12 月16 日第一批“共享单车”进入长沙,方便了长沙市民的绿色出行;随着夏季气温的升高,“共享单车”的充气轮胎容易发生爆炸的主要原因是( )A.分子停止运动B.分子质量变大C.分子本身的体积变大,分子运动速率减慢D.分子间隔变大,分子运动速率加快【解析】宏观物质由微观粒子构成,微粒间是有间隔的,温度升高间隔变大,气体的体积和压强增大,当气体膨胀发生在有限的空间里,易产生爆炸。
中考冲刺指南第五讲图形与坐标班级学号姓名一、仔细选一选(本题有10个小题,每小题3分,共30分)下面每小题给出四个选项中,只有一个是正确的.注意可以用多种不同的方法来选取正确的答案.1.(2013•湛江)在平面直角坐标系中,点A(2,﹣3)在第(D)象限.2.(2013•珠海)点(3,2)关于x轴的对称点为(A)3.(2013•邵阳)如图是我市几个旅游景点的大致位置示意图,如果用(0,0)表示新宁莨山的位置,用(1,5)表示隆回花瑶的位置,那么城市南山的位置可以表示为(C)4.(2013•遂宁)将点A(3,2)沿x轴向左平移4个单位长度得到点A′,点A′关于y轴对称的点的坐标是(C)5.(2012•深圳)已知点P(a+1,2a﹣3)关于x轴的对称点在第一象限,则a的取值范围是(B)A.a<﹣1 B.﹣1<a<C.﹣<a<1 D.a>6.(2013•泰安)在如图所示的单位正方形网格中,△ABC经过平移后得到△A1B1C1,已知在AC上一点P(2.4,2)平移后的对应点为P1,点P1绕点O逆时针旋转180°,得到对应点P2,则P2点的坐标为(C)7.(2013•东营)若定义:f(a,b)=(﹣a,b),g(m,n)=(m,﹣n),例如f(1,2)=(﹣1,2),g(﹣4,﹣5)=(﹣4,5),则g(f(2,﹣3))=(B)8.(2012•自贡)一质点P从距原点1个单位的M点处向原点方向跳动,第一次跳动到OM 的中点M3处,第二次从M3跳到OM3的中点M2处,第三次从点M2跳到OM2的中点M1处,如此不断跳动下去,则第n次跳动后,该质点到原点O的距离为(D)A.B.C.D.9..(2013•咸宁)如图,在平面直角坐标系中,以O为圆心,适当长为半径画弧,交x轴于点M,交y轴于点N,再分别以点M、N为圆心,大于MN的长为半径画弧,两弧在第二象限交于点P.若点P的坐标为(2a,b+1),则a与b的数量关系为(B)10.(2013•苏州)如图,在平面直角坐标系中,Rt△OAB的顶点A在x轴的正半轴上.顶点B的坐标为(3,),点C的坐标为(,0),点P为斜边OB上的一个动点,则PA+PC 的最小值为(B)A.B.C.D.2二、认真填一填(本题有6个小题,每小题4分,共24分)要注意认真看清题目的条件和要填写的内容,尽量完整的填写答案.12.(2011•台州)如果点P(x,y)的坐标满足x+y=xy,那么称点P为和谐点.请写出一个和谐点的坐标:开放题,答案略。
中考语法冲刺第五讲:宾语从句1一、宾语从句的分类动词后的宾语从句:I know what Yun Xiao teaches.介词后的宾语从句:The boy was interested in whatever he saw here.由形容词构成的系表结构:I am sure that I can pass the English exam easily.二、宾语从句的考点1. 时态1)主句现在(一般现在时,现在进行时,现在完成时),从句任意I remember he gave me a book yesterday.He has told me that he’ll leave for New York tomorrow.例题精讲:1. He asks me if I ____ (see) his brother yesterday.2. My father tells me that he _____ (fly) to Qingdao for a holiday.3. He wonder what I _____ (do) at five yesterday afternoon.2)主句过去(一般过去时,过去进行时),从句过去相关He told me that he would take part in the high jump.例题精讲:1. He told me that he _____ (like) playing football.2. She asked me whether I ______ (watch) TV at this time last day.3. I wanted to say that our team ______ (beat) them.3)从句为客观事实或真理,从句用一般现在时He told me that the earth is round.He told me that one and one _____ (make) two.2. 语序: 陈述句语序例题精讲:1. As middle school students, we should start thinking about ___ for our country inthe future.A. what we didB. what did we doC. what we can doD. what can we do2. - Can you tell me ___ to London?- Sure. Next month.A. when you will travelB. when will you travelC. when you travelledD. when did you travel3. - Do you know ___ our school?- The day after tomorrow.A. when the American students visitB. when the American students will visitC. when do the American students visitD. when will the American students visit3. 连接词1)that(无意义,起连接作用)2)whether/if(1. “是否” 2. “whether…or not”)3)特殊疑问词(wh...how)注意:1. whether or not / whether to do 固定搭配2. 介词后只用whether, 不用if例题精讲:1. She said ___ it wouldn’t matter much. (that/if)2. They don’t know ___ to go or wait. (if/whether)3. We are talking about ___ we’ll go back tomorrow (whether/if)4. - Could you please tell me ___?- For two weeks.A. how soon will he be backB. how soon he will be backC. how long will he be awayD. how long he will be away5. -Could you tell me ___ it’s polite to eat noisily in Japan, Kumiko?- Sure! It’s polite to do that. It means you like the food very much.A. ifB. whereC. how6. - What did Tom say to you just now, John?- He asked ___.A. why I am so happy todayB. what will I do for the weekendC. who did I play football with after schoolD. if I could go to the movies with him tonight。
第五讲内能及内能的利用疑难点突破1.分子动理论:内容:(1)物体是由大量的分子组成;(2)分子都在不停地做无规则运动;(3)分子间存在引力和斥力。
例如:花香四溢是分子不停地做无规则运动形成的;尘土飞扬是灰尘小颗粒漂浮形成的。
2.内能:(1)影响因素:内能的多少与物体的温度有关,还与物体内部分子的多少、种类、结构、状态等因素有关。
温度升高(降低),内能增加(减少),温度不变,内能不一定不变。
(2)改变的方法:做功和热传递。
注意:①做功的形式有摩擦、敲打、碾压等。
②对物体做功,物体内能增加;物体对外做功,内能减少。
③发生热传递的物体间存在温度差。
3.比热容:(1)水的比热容是 4.2×103J/(kg·℃),物质的比热容与物质的状态和种类有关。
(2)冷却塔用水作为做冷却介质,北方暖气也是利用水作为散热介质,都是利用了水的比热容较大;热容大的物质,同等条件下吸收或放出的热量多;比热容大的物质,同等条件下温度变化比较小。
4.汽油机冲程的识别:关注气门的开闭和活塞的运动方向;火花塞识别做功冲程。
5.热机效率:提高热机效率的方法:(1)让燃料充分燃烧;(2)减小机械间的摩擦;(3)减少热量损失。
实验突破实验比较不同物质的吸热能力(1)组装实验装置:要“自下而上”。
先固定下面试管的位置,确保酒精灯用外焰加热;再固定温度计的位置,确保温度计的玻璃泡不碰到试管壁。
(2)实验中的水和铁砂需要保证质量相同。
(3)实验中需要用的测量器材有天平(测量物质的质量)、停表(测量加热的时间)、温度计(测量物质的温度变化)。
(4)物体吸收热量的多少可以通过加热时间的长短来比较。
(5)组装实验装置:要“自下而上”。
先固定下面铁圈的位置,确保酒精灯用外焰加热。
(6)实验结论:物质质量和升高温度相同时,吸收热量越多,物质的吸热能力越强;物质质量和吸收热量相同时,温度变化越小,物质的吸热能力越强。
(7)t-t图像中倾斜度越小的物质吸热能力越强。
初中中考冲刺讲义第一部分语法框架第二部分语法讲解第三部分精选习题第四部分自我评估1:初中语法框架与掌握目标(1)句法简单句、并列句、复合句。
要求考生掌握英语基本句型并且能够分析句子基本结构。
如:简单句的五种形式与例句第一种:主语+谓语 SVThe barrage begins.Money talks.Oil prices soar.第二种:主语+谓语+宾语 SVO:I study English every day .第三种:主语+系动词+表语 SVP1 副词一般不做表语The news sounds very bad.Y ou don’t look well. (adj.健康的,良好的)2 of +名词These products are of high quality.Forgiveness is of high value, yet it costs nothing第四种:主语+谓语+间接宾语+直接宾语SVOO:Give me your bank card.Buy me a big house.Buy me a big house. => Buy a big house for me.第五种:主语+谓语+宾语+宾语补足语SOVCI find learning English difficult.I asked him to ring me tomorrow.The Technology Made Mobile Payments a Reality 并列句常见的连词和结构(1) 用来连接两个并列概念的连接词有and , not only…but also…, neither…nor…等,and所连接的前后分句往往表示先后关系、递进关系。
前后分句的时态往往保持一致关系,若第一个分句是祈使句,那么第二个分句用将来时。
(2) 表示在两者之间选择一个, 常用的连接词有or,otherwise,or else,either…or…等,前后分句的时态往往保持一致关系,若第一个分句是祈使句,那么第二个分句用将来时。
学科教师辅导讲义年级:初三辅导科目:化学学生姓名:课题化学基本实验教学目的1、复习初三上册各个实验2、帮助总结解题思路、归纳解题思路3、提高实验题的解题能力教学内容一、空气中氧气含量测定实验实验装置:实验原理:通过燃烧消耗集气瓶内的氧气,使集气瓶内压强变小,在大气压的作用下使水倒流进集气瓶中,流进集气瓶内水的体积就是所消耗的氧气的体积。
实验现象:红磷燃烧,产生大量的白烟,放出大量热;打开弹簧夹后,烧杯中的水沿导气管进入集气瓶中,至约占集气瓶内空间的 1/5。
实验结论:空气中氧气的体积约占 1/5。
误差分析:1、为什么有时气体减少的体积小于 1/5 呢?导致结果偏低的原因可能有:(1)红磷的量不足,瓶内氧气没有耗尽;(2)装置漏气(如塞子未塞紧、燃烧匙与橡皮塞之间有缝隙等),使外界空气进入瓶内;(3)未冷却至室温就打开弹簧夹,使进入瓶内的水的体积减少;(4)红磷中含有能和氧气反应生成气体的杂质,例如,S、C .2、该实验中有时气体减少的体积大于 1/5,又是为什么呢?原因插入燃烧匙没有立即塞进瓶塞,导致容器内气体受热膨胀,一部分跑到空气中;红磷中含有杂质,燃烧时消耗了氮气。
3.容器内剩余气体的性质:无色气体,难溶于水,不与水反应等。
资源开发:通过刚才的分析,我们知道,在做好本探究实验除用白磷代替红磷外,就是尽可能防止或减少气体泄漏的可能。
我们可以利用以下装置来进行探究:⑴用凸透镜将太阳光聚焦到白磷,使白磷燃烧。
此法可以防止燃烧匙伸入集气瓶时气体的散逸。
如图5-2。
⑵用水浴加热的办法使白磷燃烧,也可以防止燃烧匙伸入集气瓶内气体的散逸。
白磷的着火点仅40℃,水温稍高,足以使白磷着火燃烧。
如图5-3。
做此实验时,盛白磷的广口瓶不能直接放入沸水中,也以免广口瓶因骤热而爆裂。
可先用温水淋浴后,再将热水注入外面的大烧杯中。
⑶用钟罩代替集气瓶进行实验,如图5-4所示。
钟罩下方敞口,气体受热膨胀时,可将水压出一部分从产生减压作用。
初三下学期冲刺中考系列讲义(第五讲)第一部分语法+字词综合运用语法专题——宾语从句一、【单项选择】( )1. Please tell me ______ last year.A. where does your sister workB. where did your sister workC. where your sister worksD. where your sister worked( )2. She asked me if I knew _______.A.whose pen is itB. whose pen it wasC. whose pen it isD. whose pen was it( )3. You must remember _______.A. what your mother saidB. what did your mother sayC. your mother said whatD. what has your mother said( )4. Did you know ____?A. who he was looking afterB. who was he looking forC. who he is looking forD. who he is looking after( )5. Could you tell me ___?A. when will they leave BeijingB. when would they leave BeijingC. when they will leave BeijingD. when did they leave Beijing二、【综合填空】Last May I stayed in Santo Lusa for a week. That was my 6f trip there. One morning I 7s out to visit a famous museum, but I didn’t know 8w way to go , so I stopped a stranger and asked, “Excuse me, does this street leadto the Grand Museum?”“Yes, “he answered. “Go along this street and turn left at the second crossing. You can’t 9m it.”So I 10w two blocks(街区) and turned to my left, but the museum 11w there. Then I asked a second stranger. He said, “Go along this street and turn left at the second crossing."But 12a I couldn’t find the museum.I asked a third stranger and he said the same thing. This time I found the Grand Museum. Just then 13swalked up and said, “Excuse me, where’s the nearest 14b ?”I answered 15q ,”Go along this street and turn left at the second crossing!”三、【短文改错】I went to see film after supper. On my way to the 16. _______________cinema, I met an old English woman, she had lost her 17. _______________way. I gave up the chance to see the film, walking towards 18. _______________her and took her to her hotel. While go there, I told her 19. _______________great change had taken place in the past few years and she 20. _______________told me something about Britain and her family. 21. _______________Though I missed the film, however I felt very happy, 22. _______________for I not only helped the old lady out from trouble but also 23. _______________practise my spoken English. If I hadn’t worked hard at24. _______________English, I would have been able to help her. 25. _______________第二部分语篇综合提升2014重庆市中考英语试题B卷阅读理解D篇Many people have great difficulty in saying goodbye. But from goodbye moments, we can always learn something.Once, I overheard (无意中听到) a father and daughter in their goodbye moment. The father said, “I love you, I wish you enough.” The daughter answered, “Daddy, our life together has been more than enough. Your lover is all that I need. I wish you enough, too, Daddy.”They kissed and she left...The father walked over towards me. I could see he wanted and needed a cry. He came over to me and asked,“Did you ever say a forever goodbye to someone?” Before I could answer, he went on, “I am old and she lives much too far away. I know her next trip back would be for my funeral (葬礼).”“When you were saying goodbye I heard you say, “I wish you enough.” May I ask what that means?”He began to smile, “It’s a wish that has come down from my great-great-grandparents. And my parents used to say it to me.”He stopped for a moment and looked up as if trying to remember it. He smiled even more.“When we said “I wish you enough,” we were wanting the other person to have a life full of enough good things.”Then, turning towards me, he shared the following “wish” from his heart.I wish you enough sun to keep you bright.I wish you enough rain to appreciate the sun more.I wish you enough happiness to keep you alive.I wish you enough pain so that the smallest joys in life appear much bigger.I wish enough hellos to get you through the final goodbye.My friends, I wish you enough!( )26. Many people would find it difficult ___________.A. to say goodbyeB. to overhear othersC. to share their wishesD. to live too far away ( )27. How did the father get the “wish”?A. The writer wrote it for him.B. His parents passed it down to him.C. The teacher taught him at school.D. His daughter told him about it.( )28. From the passage, we may learn _______.A. the daughter didn’t understand his fatherB. the old man didn’t want to see his daughterC. the writer knew the old man very wellD. the father and daughter loved each other so much( )29. The best title of the passage may be “__________”.A. Father and DaughterB. A Difficult MomentC. Wish You EnoughD. A Trip Back Home2013年山东省聊城市初中学业水平考试阅读理解A篇My name is Sam. I joined a club called“passing help” last month. Now let me tell you why I joined it.One evening this May, on my way home my old car broken down. It was 25 miles from my home. I wanted to get a ride (搭便车), but there was no car. It was also hard to take a taxi. I decided to take a bus home.I went to a bus stop nearby .After a while, a bus came, but it did not go to my town. The bus driver was a young woman. She was kind and she told me which bus I should take. I waited there for about thirty minutes, but no bus came. At last a car came to me and a woman came out of the car.She was just the bus driver.“When I reached the bus station, I got to that the bus to your town couldn’t come,so I returned here.I just can’t leave you here,” she said, “Get in my car and I will take you you back to your home.”“It is a long way,”I said.“Come on,sir,”she said,“Let’s go.”On the way she told me a story. A few days ago, there wasn't gasin her car. An old man drove her up to a gas station and then back to her car.When we got to my home , I wanted to give her some money to thank her, but she didn’t accept it. “I only want to help others and do something nice for somebody. Pass it along.” She said.( )30. What happened to Sam one evening this May?A. He lost his way.B. His car broken down.C. He was hurt in an accident.D. He couldn't reach the gas station.( )31. Sam didn’t think of going home _______ that evening.A. by trainB. by busC. by car.D. by taxi.( )32. From the passage, we know that the young woman was _______.A.a club boss.B. a taxi driverC. a bus driver.D.a gas station worker. ( )33. The young woman wanted Sam to _______.A.give her some money.B. get on her bus.C. take her to her house.D. help others just as she did.( )34. The best title of the passage is _______.A. A kind old man.B. Getting a ride.C. Passing help.D. A broken car.【谚语集锦】1. It is more blessed to give than to receive.2. Still water runs deep.3. Two heads are better than one.4. Provide for a rainy day.5. It is better to be a head of dog than a tail of a lion.6. Every man has his price.7. Behind bad luck comes good luck.8. Where there is life, there is hope.9. A stitch in time saves nine.10.Hope for the best, prepare for the worst.*stitch /stitʃ/n.(缝纫或编织中的)一针blessed [‘blesid]adj.快乐的第三部分听力场景精选话题五自然(Nature)【重点词汇】一、自然界现象the sun the moon the earth planet starwind rain snow cloud mountainlake river sea二、植物(1) 花草树木tree bush jungle grass flower(2) 粮食crop corn rice wheat(3) 蔬菜vegetable tomato potato cabbage onionmushroom carrot lettuce green pepper broccoli (4)水果apple orange pear lemon bananawatermelon strawberry olive cherry peach 三、动物cow sheep goat horse pigdog rabbit mouse duck turkeylion tiger elephant monkey giraffekangaroo chimpanzee seal snake bearhamster penguin parrot bee antspider sea horse sea lion shark octopusgoldfish whale dolphin turtle四、季节season spring summer autumn / fall winter五、人与自然human nature man woman【重点句型】1、描述动物和植物:Animals are our friends. We should protect them. 动物是我们的朋友。