The ordinary family in colonial North America was primarily concerned with sheer physical survival and beyond that, is own economic prosperity. Thus, children were valued in terms of their productivity, and they assumed the role of producer quite early. Until they fulfilled this role, their position in the structure of the family was one of subordination ( 从属), and their psychological needs and capacities received little consideration.
As the society became more complex, the status of children in the family and in the society became more important. In the complex, technological society that the United States has become,each member must fulfill a number of personal and occupational roles and be in constant contact with a great many other members. Consequently, viewing children as potentially acceptable members of society means that they are regarded more as people in their own right than as utilitarian organisms.
This acceptance of children as equal participants in the contemporary family is reflected in the variety of statutes protecting the rights of children and in the social public welfare programs devoted exclusively to their well-being.
This new way of children and the increasing contact between the members of society has also resulted in a great interest in child-rearing techniques. People today spend a considerable portion of their time on the proper way to bring up children. It is now possible to influence the details of the socialization of another person′ s child by spreading the principle of current and fashionable theories and methods of child-rearing.
Children in colonial North America were mainly valued for their .
从第一段第二句可知，在殖民地时期，美国的儿童价值是按其生产能力来评价的。
把10gMgCl2和MgSO4的混合物溶于适量水中，滴加2mol／L的BaCl2溶液至沉淀完全，共消耗BaCl2溶液25mL。求混合物中MgCl2和MgSO4的质量各是多少克
固定在匀强磁场中的正方形导线框abcd，各边长为1．其中ab是一段电阻为R的均匀电阻丝，其余3边均为电阻可忽略的铜线。磁场的磁感应强度为B，方向垂直纸面向里。现有一与ab段的材料、粗细、长度都相同的电阻丝PQ架在导体框上，如图所示。PQ以恒定速度方向如何
一小物块以速度v0=10m／s沿光滑地面滑行，然后沿光滑曲面上升到顶部水平的高台上，并由高台上飞出，如图所示。问当高台的高度h多大时，小物块飞行的水平距离最大这个距离是多少(g=10m／s2)
某晶体盐的水溶液呈浅绿色，在此溶液中通入氯气，溶液变为棕黄色，把所得棕黄色溶液分成两份：一份加入KSCN溶液，溶液变深红色；另一份加入BaCl2溶液，产生不溶于稀HNO3的白色沉淀，则该晶体盐的化学式是_______。
欲除去乙烷中的乙烯，可将混合气体通过盛有_______的洗气瓶；欲除去乙炔中的硫化氢，可将混合气体通过盛有_______的洗气瓶。
浓硝酸常盛装在棕色瓶中，且贮放在冷暗处，原因是_______，
碳酸氢钠溶液和烧碱溶液反应的离子方程式为_______。
常温下，氨水中存在的离子有_______。
在酸或碱存在的条件下，甲酸甲酯跟水发生水解反应的化学方程式为_______。
有下列几种气体：H2、O2、HCl、NO、NH3、CH4，其中通常情况下能用来和水做“喷泉”实验的是_______。
