Which of the following is a chemical reaction? A. Melting ice B. Breaking a glass C. Rusting of iron D. Folding a paper 相关知识点: 试题来源: 解析 C。本题考查化学反应的定义。A 选项冰融化是物理变化,物质的状态发生改变但没有新物质生成。B 选项打破玻璃也是物理变化,只是物质的形状发生改变...
Which of the following is a chemical reaction? A. Melting ice B. Breaking a glass C. Rusting of iron D. Folding a piece of paper 相关知识点: 试题来源: 解析 C。本题主要考查化学变化的定义。A 选项冰融化是物理变化,物质的状态改变但没有新物质生成。B 选项打破玻璃也是物理变化,只是物质的...
In environmental protection,chemical reactions play an important role.Which of the following is a chemical reaction that can help reduce air pollution? A. Burning coal B. Planting trees C. Photo catalysis D. Dumping waste 相关知识点:
B. A change in volume. C. A change in mass. D. A change in position. 相关知识点: 试题来源: 解析 A。解析:温度变化是化学反应的一个标志。选项 B 体积变化不一定是化学反应引起的;选项 C 质量变化在一般化学反应中不太明显;选项 D 位置变化与化学反应无关。反馈 收藏 ...
Chemical reactions often involve changes in substances. Which of the following is an indication of a chemical reaction? A. Change in color B. Change in shape C. Change in size D. Change in position 相关知识点: 试题来源: 解析 A。颜色变化通常是化学反应的标志之一。形状、大小和位置的变化一般...
The development of new materials often relies on chemical reactions.Which of the following is an example of a material produced by a chemical reaction? A. Wood B. Metal C. Plastic D. Glass 相关知识点: 试题来源: 解析 C。塑料是通过化学反应生产出来的材料,而木材是天然材料,金属通常是通过冶炼...
Which of the followings are factors that affect the rate of a chemical reaction( )。 A. the concentration of the reactants B. the temperature of the system C. the catalyst of the reaction D. the concentration of the products 相关知识点: 试题来源: 解析 A,B,C 反馈 收藏 ...
Which of the following is NOT a sign of a chemical reaction? A. Color change B. Temperature rise C. Shape change D. Gas production 相关知识点: 试题来源: 解析 C。本题考查化学反应的标志。颜色变化、温度上升、产生气体都是化学反应的常见标志,形状改变通常不是化学反应的标志。
A. Decreasing temperature. B. Increasing temperature. C. Increasing the concentration of reactants. D. Using a catalyst. 相关知识点: 试题来源: 解析 A。解析:文章中提到增加温度、增加反应物浓度和使用催化剂都能加快化学反应速率,而降低温度不会加快反应速率。反馈...
1.6Which ONE of the following statements about a chemical reaction is CORRECT?The actual yield of a chemical reaction is usually ...C A equal to the percentage yield. B greater than the percentage yield. C less than the theoretical yield. D greater than the theoretical yield. 相关知识点:...