问题 填空题

全世界每年因锈蚀损失的钢铁,约占世界年产量的

1
10
.小刚同学想探究钢铁锈蚀的条件,他将三个干净的铁钉分别放入A、B、C三支试管中(如图所示),定期观察并记录现象.请回答下列问题:

(1)试管______中的铁钉最易生锈.

(2)由此可知,钢铁锈蚀的条件是______和______.

(3)铁生锈的实质是______,铁锈的主要成份是______,特点是______.

(4)请举出两种防止钢铁锈蚀的措施______;______.

答案

根据铁制品锈蚀的过程,实际上是铁与空气中的氧气,水蒸气等发生化学反应的过程,可知:

(1)试管 A中的铁钉最易生锈,故选A;

(2)根据铁制品锈蚀的过程,钢铁锈蚀的条件是氧气和水,故答案为:氧气;水;

(3)铁生锈的实质是铁被氧化,铁锈的主要成份是氧化铁,特点是疏松多孔的物质,故答案为:铁被氧化;氧化铁;疏松多孔的物质;

(4)防止钢铁锈蚀的措施:表面涂防锈油;烧涂搪瓷;制成合金;电镀其他金属等,故答案为:表面涂防锈油;烧涂搪瓷.

选择题
阅读理解

根据短文判断下列句子的正确(T)与错误(F)。

     Being safe at school and in your everyday life needs knowledge. If you remember the following information, your life will be much safer.

     ●Always notice the environment around you. You shouldn't walk alone outside. Make sure where the public

phones are. If anything dangerous happens, you can find them quickly.

     ●Don't use earphones (耳机) when running in the schoolyard or on the street. You will keep yourself from

the outside world and can be easily surprised.

     ●School bags should be carried towards the front of your body instead of putting them on your back. When buses are crowded, it is easy enough for thieves to steal the things in your bags on your back.

     ●If you are followed by a stranger, cross the street and go in the other direction (方向), let the stranger

know that you know he or she is there. Next, go and get help from others if it is necessary. Don't go home

directly. You are safer on the street than you are in your home or in a lift.

     ●If you have to take a bus to a place far away, try to get to the stop a few minutes before the buses leave.

This prevents a stranger from studying you. On buses, don't sit alone, sit behind the driver or with you friends. Don't sleep.

     ●Don't play with matches (火柴) or candles, because it may cause fire. If your house catches fire and you have to escape through smoke, move on your hands and knees with your head 30 to 60 centimetres (厘米)

above the floor. Please remember there is cleaner, cooler air near the floor during the fire.

( )1. If you find a stranger following you, go home right away.

( )2. You'd better sit after the driver when you are alone to take a bus.

( )3. It's good for you to use earphones when you are running outside. 

( )4. You shouldn't sleep all the way although it's a long bus trip.

( )5. During the fire, the cleaner and cooler air is far from the floor.

( )6. When you escape from the house on fire, you should move on your

          hands and knees with your head 300 to 600 centimetres above the floor.