问题 选择题

日常生活常见的下列物质中,属于纯净物的是( )

A.新鲜空气

B.冰和水

C.生理盐水

D.可乐饮料

答案

答案:B

题目分析:混合物是由不同种物质组成的,而纯净物是由一种物质组成的。换句话说由不同种分子构成的物质为混合物,由同种分子构成的物质为纯净物;单质是由一种元素组成的纯净物;化合物则是由不同种元素组成的纯净物。空气、盐水、饮料都是混合物,而冰就是固态的水,所以冰水是纯净物。

点评:混合物是由不同种物质组成的,而纯净物是由一种物质组成的。

填空题
单项选择题

My First Experience with AIDS Patients

我初次接触艾滋病人

by Marc Kielburger

I was ushered to the AIDS ward of a hospice in the slum.I would later learn that the ward did not exist,at least not officially.Not a single person in Thailand had AIDS,according to the Thai government at the time.People got"sick,"of course,sometimes"very sick."but no one had AIDS.The hospice was home to an ever-growing number of"very sick"people.

I entered the ward and was greeted by two Thai nurses.

"Thank goodness you are here,Marc,"said the first.

"You’re a doctor,right"

I shook my head.

"So you are a medical student then!"

I shook my head again.

"But you know medicine,right"

"Kinda,"I offered."I watch E.R.,every Thursday"

After a rapid exchange in Thai,the first one said,"NO problem.Get ready for your fou- hour medical school training!"

"But in my country medical school takes years!" I protested.

"We don’t have that long," she replied. "So we better get started. "

During the next few hours, I learned to clean wounds, administer IVs, treat bedsores, and dispense medicine. The work was punishing, made worse by stifling heat, frequent blackouts, and an incredible stench in the air. I tried desperately to hide my weak nerves and queasy stomach, but more than once dashed for the bathroom to throw up.

Just when it seemed my training was coming to an end, the nurse took me aside. "There are only two more things you need to know," she said. "On the left-hand side of the ward, you will find what we call the Exit Area. " As it turned out, she meant "exit" in the largest sense of the word. Terminally ill patients were hidden behind a curtain and then exited out of the ward after death. "The second thing you need to know," she continued, "is that we haven’t had a day off in three weeks. You’ll be looking after the ward by yourself for the next shift. "

My jaw dropped.

"Don’t worry, Mare," said the other nurse, patting me on the shoulder before turning to leave. "Think of this as the beginning of your residency !" And with that, they walked out. Alone and petrified, I tried unsuccessfully to keep calm.

I counted to twenty-four. That’s how many AIDS patients were in my charge. What am I going to do I thought. What can I do I fell back on my training with the Canadian government and put my talents to work. I served patients water-some with ice, some without. Next, I tried to cheer up everyone, myself included, giving enthusiastic high-fives to patient after patient. Soon enough, everyone was laughing. Some were laughing with me, others most definitely at me, but I didn’t care. As long as I could keep people smiling, I was sure it would all be fine. And it was. Until a short while later, when a patient in the Exit Area began to choke. He had fluid in his lungs and could not breathe. As I crossed the floor, I could hear the man gasping for air. Fumbling and scared, I pulled back the curtain and administered the medicine the nurses had recommended. The man didn’t respond. With nothing left to offer, I sat down and held his hand, looking into his eyes as he breathed heavily for a while and then stopped. Watching him slip away, I was hit by a feeling of anguish such as I’d never felt, either before or since. It haunts me to this day.

Judging from the passage, what is the writer most likely to be ()

A.A doctor

B.A medical student

C.A volunteer

D.A government official