Physical Changes versus Chemical Changes · 物理变化与化学变化
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| physical change/ˈfɪzɪkl tʃeɪndʒ/ | 物理变化 | wù lǐ biàn huà |
| chemical change/ˈkemɪkl tʃeɪndʒ/ | 化学变化 | huà xué biàn huà |
Two kinds of change
- Ice melting and paper burning both transform something.
- But only one makes a brand-new substance.
- Melt the ice and you can freeze it right back.
- Burn the paper and the ash will never be paper again.
两类变化
- 冰融化和纸燃烧都在改变某样东西。
- 但只有一种会生成全新的物质。
- 把冰融化,你能马上把它冻回去。
- 把纸烧了,灰烬再也不会变回纸。
A physical change
- A physical change 物理变化 alters form but not identity.
- Melting, boiling, dissolving, or cutting -- the same substance throughout.
- It is often easy to reverse.
物理变化
- 物理变化改变形态,但不改变身份。
- 融化、沸腾、溶解或切割——自始至终是同一种物质。
- 它通常容易逆转。
Ice melting into water is a... · 冰融化成水是...
It is still water, just a different state -- physical. · 它仍然是水，只是状态不同——物理变化。
A chemical change
- A chemical change 化学变化 makes new substances with new properties.
- Burning, rusting, and cooking rearrange atoms into new compounds.
- It is usually hard to reverse.
化学变化
- 化学变化生成具有新性质的新物质。
- 燃烧、生锈和烹饪把原子重新排列成新化合物。
- 它通常难以逆转。
Physical or chemical change? · 物理变化还是化学变化？
Sort each change. · 对每种变化进行分类。
Burning wood into ash and smoke is a... · 木材燃烧成灰烬和烟雾是...
New substances (ash, gases) form, so it is chemical. · 生成了新物质（灰烬、气体），因此是化学变化。
Select all · 所有 chemical changes. · 选择 所有 化学变化。
Rusting and souring form new substances; chopping is physical. · 生锈和变酸生成新物质；砍木头是物理变化。
How to tell
- Ask whether the substances after the change differ from before.
- A new colour, a gas, or a solid appearing hints at a chemical change.
- If only the shape or state changed, it is physical.
如何判断
- 问一问:变化后的物质与之前不同吗?
- 出现新颜色、气体或固体,提示化学变化。
- 如果只是形状或状态改变,那是物理变化。
The key test for a chemical change is whether... · 判断化学变化的关键测试是是否...
A genuinely new substance signals a chemical change. · 真正的新物质表明发生了化学变化。
Is dissolving salt in water physical or chemical?
- The salt separates into ions but is still salt.
- Evaporate the water and the salt returns, so it is physical.
把盐溶于水是物理变化还是化学变化?
- 盐分离成离子,但仍然是盐。
- 把水蒸干,盐又回来了,所以是物理变化。
Dissolving salt in water is usually a physical change because the salt can be recovered. · 盐溶解在水中通常是物理变化，因为盐可以被回收。
Evaporating the water returns the original salt. · 蒸发水分可以恢复原来的盐。
A change of state such as boiling is a ____ change. · 像沸腾这样的状态变化是 ____ 变化。
Boiling changes state but not the substance's identity. · 沸腾改变状态但不改变物质的本质。
A change of state (melting, boiling) is physical -- the substance is unchanged, just rearranged. Dissolving is usually physical too, since you can recover the solute. The real test is: did a new substance with new properties form? If yes, it is chemical.
状态变化(融化、沸腾)是物理变化——物质不变,只是重新排列。溶解通常也是物理变化,因为你能回收溶质。真正的判据是:是否生成了具有新性质的新物质?若是,则为化学变化。
A physical change alters form but not identity (melting, dissolving) and is usually reversible. A chemical change makes new substances with new properties (burning, rusting) and is hard to reverse. The test is whether a genuinely new substance appeared.
物理变化改变形态但不改变身份(融化、溶解),通常可逆。化学变化生成具有新性质的新物质(燃烧、生锈),难以逆转。判据是是否出现了真正的新物质。