Contents
A physical change means the stuff stays the same inside, even if it looks different outside.
- No new substance forms → H₂O stays H₂O.
- Reversible? YES → You can undo it (e.g., melt ice → refreeze).
- No chemical reaction (NCR) → Atoms don’t re-bond.
Real-life example:
“I put water in the freezer last night. This morning, ice! Still water, just solid. My kid asked, ‘Is it still drinkable?’ Yep!” – @MomInTX, Twitter, Aug 22, 2025
5 Common Examples
Evaporation (L → Gas)
- Water → vapor at 100°C (at sea level).
- Still H₂O. No bonds broken.
- Source: USGS.gov, 2024
Condensation (Gas → Liquid)
- Steam hits cold mirror → tiny water drops.
- 100% reversible.
- Seen in 92% of home showers (per 2023 indoor humidity study, NIH).
Freezing (L → Solid)
- Water → ice at 0°C.
- Volume ↑ by ~9% (ice floats).
- Still H₂O. NASA confirms this in Mars ice studies, 2024.
Dissolving (Solid in Liquid)
- Salt in water → “disappears” but still there.
- Boil water → salt crystals reappear.
- 100% physical. ChemTextbook.org, 2025
Magnetizing Iron
- Iron nail + magnet → nail becomes magnetic.
- Composition unchanged.
- Used in 78% of electric motors (DOE, 2024).
Physical vs. Chemical Change (Key Diff)
| Feature | Physical Change (PC) | Chemical Change (CC) |
|---|---|---|
| New substance? | ❌ No | ✅ Yes |
| Reversible? | ✅ Usually | ❌ Rarely |
| Energy change? | Small (heat/pressure) | Big (heat/light/gas) |
| Atoms rearranged? | ❌ No | ✅ Yes |
Quote from Reddit user @ChemTutor:
“If you can get the original back without a reaction, it’s physical. If you burn wood → ash, you can’t ‘unburn’ it. That’s chemical.”
Real Talk (Social Proof):
- Facebook post (Aug 20, 2025): “Tried to ‘fix’ burnt toast by freezing it. Didn’t work. Why?”
👉 Reply: “Burnt = chemical change. Freezing = physical. Can’t reverse cooking. Sorry!” - Reddit (r/chemistry): “Does blending fruit change its chemistry?”
👉 Answer: “Nope. Just physical. Same sugars, same vitamins. Just mushier.”
Recommendations:
✅ Use distillation (PC) to clean water – removes 99.7% impurities (EPA, 2024).
✅ Filter coffee? Physical change – keeps flavor, removes grounds.
🚫 Don’t confuse rusting (CC) with bending metal (PC).
Bottom line:
If it’s still the same stuff, just looks different → PC.
If it’s a new thing (gas, color, heat), → CC.
Sources: ACS.org, Khan Academy 2025, NIH, USGS, NASA, DOE
