【题目】19世纪末，物理学家瑞利在研究中发现，从空气中分离得到的氮气密度，与从含氮物质制得的氮气密度有0.0064 kg/m3的差异，他没有放过这一发现，在化学家拉姆塞的合作下，经过十几年的努力，于1894年发现了空气中的氩气。下列说法正确的是________(填序号)。

①氩是一种化学性质极不活泼的气体；

②瑞利从空气中分离的氮气是纯净物；

③19世纪末以前，人们认为空气由氧气和氮气组成的；

④瑞利发现，从含氮物质制得的氮气密度大于从空气中分离的氮气的密度。

【题目】空气的主要成分①氧气、②氮气、③稀有气体、④二氧化碳及其他气体杂质，按体积分数由大到小的顺序排列正确的是(　　)。

A. ①②③④ B. ②①③④

C. ①②④③ D. ②①④③

【题目】下列关于空气成分的叙述正确的是( )。

A．空气中氮气和氧气的体积比约为4∶1

B．空气的成分按质量计算，氮气占78%，氧气占21%

C．从液态空气中能分离出氮气，不能分离出氧气和稀有气体

D．空气中含量最多且性质又不活泼的是稀有气体

【题目】My uncle likes sports very much. He loves soccer ball, basketball, baseball, tennis and more. He plays baseball and basketball very well. He likes to watch the sports games on TV. He plays sports every day. He has a small(小的) sports collection. He has 3 tennis rackets, 2 baseballs, 3 basketballs and a soccer ball.

根据短文内容判断正(T)误(F)。

【1】My uncle doesn’t like sports, but he has a sports collection.

【2】He plays baseball and basketball very well.

【3】He likes to watch the sports collection on TV.

【4】He watches TV and plays sports every day.

【5】His collection is small: 3 tennis rackets, 2 baseballs, 3 basketballs and a soccer ball.

【题目】I am an American boy. ___name is Paul. I am 12 . I___two friends, Sally and Mona. They’re___. We play sports___. We play soccer, basketball, volleyball and____ Sally___a sports collection（收藏）.___has seven soccer balls,___basketball, four volleyballs, and six tennis rackets. We often(经常)___volleyball on TV. What sports____you often play?

【1】A. My B. His C. Her

【2】A. am B. do C. have

【3】A. them B. brothers C. sisters

【4】A. everyday B. every day C. morning

【5】A. sports B. more C. them

【6】A. doesn’t have B. plays C. has

【7】A. He B. She C. Paul

【8】A. one B. zero C. three

【9】A. play B. have C. watch

【10】A. do B. does C. don’t

【题目】

【1】a，v,e,h, _____

【2】e,t,n,n,s,i _______

【3】l,b,a,v,o,l,y,e, l,l________

【4】u,f,n ______

【5】o,u,s,n,d ______

【6】a,c,s,s,l _______

【7】a,e,l,t_____

【8】e,s,a,m_______

【9】i,w,h,t ________

【10】b,o,i,n,r,g_______

【题目】–Let’s play computer games. - _______.

A. Yes, we do B. No, we don’t C. That sounds good.

【题目】下列物质中属于混合物的是( )。

A．氮气 B．二氧化碳

C．空气 D．氧气

【题目】有两个集气瓶，分别充满空气和氮气，试用简单的方法加以鉴别。

________________________________________________________________________。

【题目】下列事例中，能增大压强的是（ ）

A、把书包带做得宽些 B、在坦克的轮子上安装履带

C、刀、斧、剪的刃磨得很薄 D、在铁路的钢轨下铺上枕木