Get the instructions you need to conduct them and learn about additional educational resources you can use to enhance students' understanding of chemical change. Easy Blow Balloons Kids can discover an easy way to blow up balloons with this experiment that involves a chemical reaction between ...
Scientists watch the changes of a chemical reaction. This is ___. A. experiment B. observation C. interview D. survey 相关知识点: 试题来源: 解析 B。观察化学反应的变化是观察法。选项 A 实验法会有变量控制等操作;选项 C 采访法不适用;选项 D 调查法不适用。反馈 收藏 ...
chemical change C. mixture formation D. separation of substances 相关知识点: 试题来源: 解析 B。在化学实验中,如果一种物质改变颜色,这可能表明发生了化学变化(chemical change)。物理变化(physical change)通常不会导致物质颜色的改变。混合物的形成(mixture formation)不一定会有颜色变化。物质的分离(separation...
A。解析:在化学实验中,我们经常仔细地注意溶液的颜色变化。notice有注意到、察觉到的意思,强调有意识地去关注。find是找到,侧重于结果。recognize是认出,通常是对已经知道的事物再次识别。discover是发现新事物,这里不是发现新的颜色,而是关注颜色变化,所以notice最合适。反馈...
相关知识点: 试题来源: 解析 A。解析:在化学萃取实验中,第一个重要步骤是添加萃取溶剂。选项B,分离两层不混溶的液体是在加入萃取溶剂之后的操作。选项C,温和加热混合物不是首要步骤。选项D,测量混合物的密度不是化学萃取实验的首要操作。反馈 收藏
In the chemical experiment,the temperature was gradually increased.What can be expected to happen as the temperature rises? A. The reaction rate decreases. B. The reaction rate remains unchanged. C. The reaction rate increases. D. The reaction stops completely. 相关知识点: ...
clean it up immediately C. wait for someone else to do it D. ignore it and continue 相关知识点: 试题来源: 解析 B。选项 A 走开不管不顾很危险。选项 B 立即清理是正确的做法,防止化学药品造成更大的危害。选项 C 等别人来做可能会耽误时间且增加危险。选项 D 忽视并继续实验很危险。反馈 收藏 ...
A. Chemical experiment B. Chemistry experiment C. Chemical experiments D. Chemistry E. xperiments 相关知识点: 试题来源: 解析 B。“化学实验”常用“chemistry experiment”,“chemical”是“化学的”,“chemistry”是“化学”,这里需要用“chemistry”,实验一般用单数,所以选 B。反馈...
Before starting a chemical reaction experiment, it is important to ___. A. wear protective clothing B. record the initial data C. mix the chemicals randomly D. turn on all the instruments 相关知识点: 试题来源: 解析 A。解析:在开始化学反应实验前,重要的是穿上防护服确保安全。选项 B 记录...
In a chemical experiment, we often use litmus paper to test whether a solution is acidic or basic. Litmus paper turns red in an ___ solution. A. alkaline B. acidic C. neutral D. salt 相关知识点: 试题来源: 解析 B。解析:在化学中,石蕊试纸在酸性溶液中会变红,碱性溶液中变蓝,中性溶液中...