什么是放热反应和吸热反应？
What are exothermic and endothermic reactions?
放热反应在过程中向外界释放热量，如燃烧和大多数中和反应。吸热反应则需要从外界吸收热量才能进行，如光合作用。
Exothermic reactions release heat to the surroundings, such as combustion and most neutralization reactions. Endothermic reactions absorb heat from the surroundings, such as photosynthesis.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#放热 #吸热 #热量
什么是质量守恒定律？
What is the law of conservation of mass?
质量守恒定律指出，在化学反应中参加反应的各物质总质量等于反应后生成物的总质量。这是因为反应只是原子重新组合，原子本身不增不减。
The law of conservation of mass states that in a chemical reaction the total mass of reactants equals the total mass of products. This is because the reaction only rearranges atoms without creating or destroying them.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#质量守恒 #原子 #化学计量
什么是化学反应？
What is a chemical reaction?
化学反应是物质发生变化、生成新物质的过程，反应前后原子的种类和数目不变。例如氢气燃烧生成水就是一种化学反应。
A chemical reaction is a process in which substances change and new substances are formed, while the types and numbers of atoms stay the same. For example, hydrogen burning to form water is a chemical reaction.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#化学反应 #新物质 #原子守恒
燃烧需要什么条件？
What conditions are needed for burning?
燃烧通常需要可燃物、氧气（或助燃物）和足够高的温度三者同时存在。缺少了其中任何一个，火就会熄灭。
Burning usually requires three things at once: a fuel, oxygen or another supporter of combustion, and enough heat. Remove any one of them and the fire goes out.
难度 入门 · 适合 小学低段(6-8)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#燃烧 #氧气 #温度
化学反应通常有哪些类型？
What are the common types of chemical reactions?
常见的反应类型有化合、分解、置换和复分解反应。化合是多种物质生成一种，分解是一种物质分成多种，置换是单质替换化合物中的元素，复分解是两种化合物互相交换成分。
Common reaction types include combination, decomposition, single replacement, and double replacement. Combination joins substances into one, decomposition splits one into many, single replacement swaps an element in a compound, and double replacement exchanges parts between two compounds.
难度 入门 · 适合 小学高段(9-12)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#反应类型 #化合 #分解
蜡烛燃烧是化学反应吗？
Is burning a candle a chemical reaction?
是的。蜡烛的蜡与空气中的氧气反应，生成二氧化碳和水，同时放出光和热。因为产生了与原来不同的新物质，所以属于化学反应。
Yes. The wax of a candle reacts with oxygen in the air to form carbon dioxide and water while releasing light and heat. Because new substances different from the original are produced, it is a chemical reaction.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#蜡烛 #燃烧 #二氧化碳