【实验过程】(实验中的热损失及热胀冷缩对实验的影响忽略不计)
①将一定质量温度为t1的冷水装入一个双层玻璃真空保温杯中,液面如图甲所示位置,标记为A。
②向杯中插入导管,将100℃的水蒸气通入保温杯的冷水中(水蒸气全部被吸收),发现杯中水面明显上升。
③一段时间后,停止通入水蒸气,移出导管后,杯中液面位置如图乙所示,标记为B,再测出此时杯中水的温度为t2 , 比较发现t2高于t1。
A plant is a living thing. It uses its many parts to grow from a small seed to a large plant. Each part helps the plant stay healthy. Plants also need sunlight to grow. They get light from the sun and minerals from the soil. These things help the plant stay alive and grow. 
They use sunlight, water and air to make a plant's food. |
Flowers Flowers make seeds that can grow into new plants. |
Stem The stem helps hold the plant up. It moves the food and water from the roots to the other parts of the plant |
Fruit Some plants have fruit. The fruit grows around the seeds and keeps them safe. |
Seeds Seeds can grow into new plants. |
Roots A plant grows roots under the ground. The roots hold the plant in place. |
B . CH4的球棍模型:
C . 乙烯的分子比例模型:
D . 氮气的电子式:
在传统结构中,每一家以自己的地位作中心,①,这个圈子是“街坊”。有喜事要请酒,生了孩子要送红蛋,有丧事要出来助殓、抬棺材,是生活上的互助机构。可是这不是一个固定的团体,而是一个范围。范围的大小也要依着②而定。有势力的人家的街坊可以遍及全村,穷苦人家的街坊只是比邻的两三家。这和我们的亲属圈子一般的。像贾家的大观园里,可以住着姑表林黛玉,姨表薛宝钗,后来更多了,什么宝琴、岫烟,凡是拉得上亲戚的,都包容得下。可是势力一变,树倒猢狲散,缩成一小团。到极端时,可以像苏秦潦倒归来,“妻不以为夫,嫂不以为叔”。中国传统结构中的差序格局③。在乡下,家庭可以很小,而一到有钱的地主和官僚阶层,可以大到像个小国。中国人也特别对世态炎凉有感触,正因为这富于伸缩的社会圈子会因中心势力的变化而大小。