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)

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