Every day you see matter changing around you - ice...
Science2 pregledi·Ažurirano Jun 12, 2026·5 straniceUnderstanding Chemical and Physical Changes
1 / 5
1
of 5
Understanding the Basics
You'll find this topic everywhere in science, so getting these definitions right will make everything else much easier. A physical change happens when something looks different but is still the same substance underneath - like ice melting into water (it's still H₂O). A chemical change creates completely new substances with different properties.
Think of it this way: if you can easily undo the change, it's probably physical. If you can't turn it back to what it was, it's likely chemical.
The key players in chemical changes are reactants (what you start with) and products (what you end up with). Most physical changes are reversible, whilst chemical changes are usually irreversible.
Top Tip: Ask yourself "Is a new substance formed?" - this is the ultimate test for spotting chemical changes.
2
of 5
Spotting the Differences
This comparison table is absolutely essential for your exams - you'll definitely need to know these differences. Physical changes keep the same substance but change its form (like crushing ice or boiling water). Chemical changes create entirely new substances with different properties.
The big giveaway is reversibility. You can easily freeze water back into ice, but you can't turn ash back into wood. Energy changes happen in both types, but chemical reactions often produce much more dramatic energy changes.
Don't worry about the mass though - it's always conserved in both types of changes. The total mass before equals the total mass after, every single time.
Remember: Changes of state (melting, freezing, boiling) are ALWAYS physical changes, no matter how dramatic they look.
3
of 5
Signs of Chemical Reactions
When you're in the lab, these signs will help you spot chemical reactions happening right before your eyes. Look for colour changes (like metal turning rusty), gas production (bubbling or fizzing), or a precipitate forming (when a solid suddenly appears in a clear liquid).
Energy changes are huge clues too. Exothermic reactions give out heat and warm up the container, whilst endothermic reactions absorb heat and cool things down. You might also notice light, sound, or new smells appearing.
Here's the catch though - one sign alone might not be enough. Boiling water produces bubbles, but that's still a physical change. You need to think about whether a genuinely new substance is being created.
Lab Alert: Don't just rely on one sign - look at the whole picture to determine if new substances are actually forming.
4
of 5
Real-World Examples
Let's test your understanding with some everyday scenarios. Dissolving salt in water is physical because no new substances form - you can get your salt back by evaporating the water. The salt and water are still chemically the same.
Frying an egg is definitely chemical. The clear, runny egg white becomes solid and white through heat, and the proteins change permanently. You'll never turn that fried egg back into a raw one!
Rusting happens when iron reacts with oxygen and water to form iron oxide - a completely new substance that's flaky and reddish-brown. Making tea is mostly physical (boiling, dissolving, diffusion), though some tiny chemical processes might occur with the tea compounds.
Exam Strategy: Always explain your reasoning - don't just say "physical" or "chemical", explain why based on whether new substances form.
5
of 5
Key Points for Success
You've got this! The Law of Conservation of Mass applies to everything - mass is never lost or gained, whether it's physical or chemical changes. Remember that dissolving is always physical (the substance is just spread out, not changed), and all changes of state are physical.
For chemical changes, watch for the classic signs: fizzing, colour changes, precipitates, and energy changes. The ultimate question remains: "Is a new substance formed?"
Keep practising with everyday examples around you. Is cooking chemical or physical? What about breaking glass? The more you apply these concepts to real life, the more confident you'll become.
Confidence Boost: Once you master the "new substance" rule, you'll find this topic much easier than it first appears!
Mislili smo da nikad nećeš pitati...
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Aplikacija je super laka za korišćenje i odlično dizajnirana. Našao sam sve što mi je trebalo i dosta sam naučio iz prezentacija! Definitivno ću koristiti aplikaciju za školski zadatak! A naravno, pomaže i kao inspiracija.
Stefan SiOS korisnik
Ova aplikacija je stvarno odlična. Tu je toliko beleški za učenje i pomoći [...]. Na primer, problem mi je francuski, a aplikacija ima toliko opcija za pomoć. Zahvaljujući ovoj aplikaciji, poboljšao sam francuski. Preporučio bih je svima.
Samantha KlichAndroid korisnik
Vau, stvarno sam oduševljena. Probala sam aplikaciju jer sam je videla u reklamama mnogo puta i bila sam potpuno šokirana. Ova aplikacija je POMOĆ koju želiš za školu i pre svega, nudi toliko stvari, kao što su vežbe i sažeci, što mi je lično bilo VEOMA korisno.
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Science2 pregledi·Ažurirano Jun 12, 2026·5 straniceUnderstanding Chemical and Physical Changes
Every day you see matter changing around you - ice melting in your drink, bread toasting, or your bike getting rusty. Understanding whether these are physical or chemical changes is crucial for understanding how the world works and will help...
1
of 5
Registruj se da vidiš sadržaj. Besplatno je!
- Pristup svim dokumentima
- Poboljšaj svoje ocene
- Pridruži se milionima učenika
Understanding the Basics
You'll find this topic everywhere in science, so getting these definitions right will make everything else much easier. A physical change happens when something looks different but is still the same substance underneath - like ice melting into water (it's still H₂O). A chemical change creates completely new substances with different properties.
Think of it this way: if you can easily undo the change, it's probably physical. If you can't turn it back to what it was, it's likely chemical.
The key players in chemical changes are reactants (what you start with) and products (what you end up with). Most physical changes are reversible, whilst chemical changes are usually irreversible.
Top Tip: Ask yourself "Is a new substance formed?" - this is the ultimate test for spotting chemical changes.
2
of 5Registruj se da vidiš sadržaj. Besplatno je!
- Pristup svim dokumentima
- Poboljšaj svoje ocene
- Pridruži se milionima učenika
Spotting the Differences
This comparison table is absolutely essential for your exams - you'll definitely need to know these differences. Physical changes keep the same substance but change its form (like crushing ice or boiling water). Chemical changes create entirely new substances with different properties.
The big giveaway is reversibility. You can easily freeze water back into ice, but you can't turn ash back into wood. Energy changes happen in both types, but chemical reactions often produce much more dramatic energy changes.
Don't worry about the mass though - it's always conserved in both types of changes. The total mass before equals the total mass after, every single time.
Remember: Changes of state (melting, freezing, boiling) are ALWAYS physical changes, no matter how dramatic they look.
3
of 5Registruj se da vidiš sadržaj. Besplatno je!
- Pristup svim dokumentima
- Poboljšaj svoje ocene
- Pridruži se milionima učenika
Signs of Chemical Reactions
When you're in the lab, these signs will help you spot chemical reactions happening right before your eyes. Look for colour changes (like metal turning rusty), gas production (bubbling or fizzing), or a precipitate forming (when a solid suddenly appears in a clear liquid).
Energy changes are huge clues too. Exothermic reactions give out heat and warm up the container, whilst endothermic reactions absorb heat and cool things down. You might also notice light, sound, or new smells appearing.
Here's the catch though - one sign alone might not be enough. Boiling water produces bubbles, but that's still a physical change. You need to think about whether a genuinely new substance is being created.
Lab Alert: Don't just rely on one sign - look at the whole picture to determine if new substances are actually forming.
4
of 5Registruj se da vidiš sadržaj. Besplatno je!
- Pristup svim dokumentima
- Poboljšaj svoje ocene
- Pridruži se milionima učenika
Real-World Examples
Let's test your understanding with some everyday scenarios. Dissolving salt in water is physical because no new substances form - you can get your salt back by evaporating the water. The salt and water are still chemically the same.
Frying an egg is definitely chemical. The clear, runny egg white becomes solid and white through heat, and the proteins change permanently. You'll never turn that fried egg back into a raw one!
Rusting happens when iron reacts with oxygen and water to form iron oxide - a completely new substance that's flaky and reddish-brown. Making tea is mostly physical (boiling, dissolving, diffusion), though some tiny chemical processes might occur with the tea compounds.
Exam Strategy: Always explain your reasoning - don't just say "physical" or "chemical", explain why based on whether new substances form.
5
of 5Registruj se da vidiš sadržaj. Besplatno je!
- Pristup svim dokumentima
- Poboljšaj svoje ocene
- Pridruži se milionima učenika
Key Points for Success
You've got this! The Law of Conservation of Mass applies to everything - mass is never lost or gained, whether it's physical or chemical changes. Remember that dissolving is always physical (the substance is just spread out, not changed), and all changes of state are physical.
For chemical changes, watch for the classic signs: fizzing, colour changes, precipitates, and energy changes. The ultimate question remains: "Is a new substance formed?"
Keep practising with everyday examples around you. Is cooking chemical or physical? What about breaking glass? The more you apply these concepts to real life, the more confident you'll become.
Confidence Boost: Once you master the "new substance" rule, you'll find this topic much easier than it first appears!
Mislili smo da nikad nećeš pitati...
Šta je Knowunity AI companion?
Naš AI Companion je AI alat fokusiran na učenike koji nudi više od samih odgovora. Napravljen na milionima Knowunity resursa, pruža relevantne informacije, personalizovane planove učenja, kvizove i sadržaj direktno u chatu, prilagođavajući se tvom individualnom putu učenja.
Gde mogu da preuzmem Knowunity aplikaciju?
Možeš preuzeti aplikaciju sa Google Play Store-a i Apple App Store-a.
Da li je Knowunity stvarno besplatan?
Tako je! Uživaj u besplatnom pristupu sadržaju za učenje, povezuj se sa drugim učenicima i dobijaj trenutnu pomoć – sve na dohvat ruke.
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Includes poem in English and Irish, theme, key words & phrases
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Comparative Study : Cultural Context : Shawshank Redemption, Sive and Small Things Like These
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Notes on mo ghrá-sa
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6th Year1320
Ne možeš da nađeš ono što tražiš? Istražuj druge predmete.
Učenici nas obožavaju — i ti ćeš takođe.
4.6/5App Store
4.7/5Google Play
Aplikacija je super laka za korišćenje i odlično dizajnirana. Našao sam sve što mi je trebalo i dosta sam naučio iz prezentacija! Definitivno ću koristiti aplikaciju za školski zadatak! A naravno, pomaže i kao inspiracija.
Stefan SiOS korisnik
Ova aplikacija je stvarno odlična. Tu je toliko beleški za učenje i pomoći [...]. Na primer, problem mi je francuski, a aplikacija ima toliko opcija za pomoć. Zahvaljujući ovoj aplikaciji, poboljšao sam francuski. Preporučio bih je svima.
Samantha KlichAndroid korisnik
Vau, stvarno sam oduševljena. Probala sam aplikaciju jer sam je videla u reklamama mnogo puta i bila sam potpuno šokirana. Ova aplikacija je POMOĆ koju želiš za školu i pre svega, nudi toliko stvari, kao što su vežbe i sažeci, što mi je lično bilo VEOMA korisno.
AnaiOS korisnik