Recognizing a Chemical Reaction · 识别化学反应
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| chemical reaction/ˈkemɪkl rɪˈækʃn/ | 化学反应 | huà xué fǎn yìng |
| law of conservation of mass/lɔː ɒv ˌkɒnsəˈveɪʃn ɒv mæs/ | 质量守恒定律 | zhì liàng shǒu héng dìng lǜ |
Signs that something new was made
- Bubbles fizz up when vinegar meets baking soda.
- A nail turns orange-brown after weeks in the rain.
- A glowstick suddenly shines without any heat.
- Certain clues reveal that new substances have formed.
有新东西生成的迹象
- 醋遇到小苏打时冒起泡泡。
- 钉子在雨中几周后变成橙棕色。
- 荧光棒不需任何热量就忽然发光。
- 某些线索揭示新物质已经形成。
Clues of a reaction
- A chemical reaction 化学反应 makes new substances from old ones.
- Watch for a colour change, a gas, a precipitate, or heat and light.
- These signs hint that bonds broke and reformed.
反应的线索
- 化学反应用旧物质生成新物质。
- 留意颜色变化、气体、沉淀,或热和光。
- 这些迹象暗示键断开又重新形成。
Select all · 所有 signs that suggest a chemical reaction. · 选择所有暗示化学反应的迹象。
Colour change, gas, and a precipitate all hint at new substances. · 颜色变化、气体和沉淀都暗示有新物质生成。
Mass is conserved
- Atoms are only rearranged, never created or destroyed.
- So the total mass stays the same before and after.
- This is the law of conservation of mass 质量守恒定律.
质量守恒
- 原子只是被重新排列,绝不会被创造或消灭。
- 所以反应前后总质量保持不变。
- 这就是质量守恒定律。
In a chemical reaction, the total mass of reactants equals the total mass of products. · 在化学反应中，反应物的总质量等于产物的总质量。
Atoms are conserved, so mass is conserved. · 原子守恒，因此质量守恒。
Mass is conserved even when a ____ escapes during the reaction. · 即使反应过程中有____逸出，质量仍然守恒。
The escaped gas still has mass, so total mass is unchanged. · 逸出的气体仍有质量，因此总质量不变。
Balancing the equation
- A balanced equation has equal atoms of each element on both sides.
- Adjust the coefficients (never the subscripts) to balance it.
- $2\text{H}_2 + \text{O}_2 \to 2\text{H}_2\text{O}$ is balanced.
配平方程
- 配平的方程两边每种元素的原子数相等。
- 调整系数(绝不是下标)来配平它。
- $2\text{H}_2 + \text{O}_2 \to 2\text{H}_2\text{O}$ 是配平的。
Chemical reaction or not? · 是化学反应还是不是？
Decide whether each observation is a sign of a chemical reaction or just a physical change. · 判断每个观察结果是化学反应的迹象还是仅仅是物理变化。
To balance an equation, you adjust the... · 要平衡方程式，你需要调整...
Change coefficients only; changing subscripts changes the substance. · 只改变系数；改变下标会改变物质本身。
Changing a subscript to balance an equation is allowed. · 改变下标来平衡方程式是被允许的。
Changing a subscript changes the compound itself, so it is not allowed. · 改变下标会改变化合物本身，因此是不允许的。
Is $\text{H}_2 + \text{O}_2 \to \text{H}_2\text{O}$ balanced?
- The left has 2 oxygen atoms; the right has 1, so it is not balanced.
- Fix it with coefficients: $2\text{H}_2 + \text{O}_2 \to 2\text{H}_2\text{O}$.
$\text{H}_2 + \text{O}_2 \to \text{H}_2\text{O}$ 配平了吗?
- 左边有 2 个氧原子;右边有 1 个,所以没配平。
- 用系数修正:$2\text{H}_2 + \text{O}_2 \to 2\text{H}_2\text{O}$。
In $2\text{H}_2 + \text{O}_2 \to 2\text{H}_2\text{O}$, how many oxygen atoms are on each side? · 在 $2\text{H}_2 + \text{O}_2 \to 2\text{H}_2\text{O}$ 中，每侧有多少个氧原子？
$\text{O}_2$ has 2 O; $2\text{H}_2\text{O}$ has 2 O -- balanced. · $\text{O}_2$ 有 2 个 O；$2\text{H}_2\text{O}$ 有 2 个 O ——已平衡。
Balance by changing coefficients (the big numbers in front), never subscripts -- changing a subscript changes the substance itself. A single sign like bubbles suggests but does not prove a chemical change (dissolving can fizz too). And mass is always conserved, even when a gas escapes.
通过改变系数(前面的大数字)来配平,绝不改下标——改下标就改变了物质本身。单一迹象(如泡泡)提示但不能证明化学变化(溶解也会冒泡)。而且质量总是守恒的,即使有气体逸出。
A chemical reaction turns old substances into new ones, hinted at by colour change, gas, a precipitate, or heat and light. Atoms are only rearranged, so the law of conservation of mass holds. Balance an equation by adjusting coefficients, never subscripts.
化学反应把旧物质变成新物质,由颜色变化、气体、沉淀或热和光来提示。原子只是被重新排列,所以质量守恒定律成立。配平方程要调整系数,绝不改下标。