Worksheet on identifying chemical and physical changes in matter.
A worksheet titled "Chemical and Physical Changes" with a list of ten scenarios to identify as chemical or physical changes, including examples like heating water into steam and iron rusting, accompanied by a molecular diagram.
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Show Answer Key & Explanations
Step-by-step solution for: Chemical and Physical Changes of Matter
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Show Answer Key & Explanations
Step-by-step solution for: Chemical and Physical Changes of Matter
Here's the solution to the worksheet, with explanations for each item:
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1. Heating water into steam → Physical Change
*Explanation:* This is a change of state (liquid to gas). The water molecules (H₂O) remain chemically unchanged — no new substances are formed. Only the physical form and energy content change.
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2. Milk going sour → Chemical Change
*Explanation:* Souring milk involves bacterial fermentation that converts lactose into lactic acid. This creates new chemical compounds and changes the taste, smell, and texture — indicating a chemical reaction has occurred.
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3. Dissolving sugar in water → Physical Change
*Explanation:* Sugar molecules disperse among water molecules but do not react chemically. You can recover the sugar by evaporating the water, proving no new substance was formed.
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4. Iron rusting → Chemical Change
*Explanation:* Rust is iron oxide (Fe₂O₃), formed when iron reacts with oxygen and water. This is a classic example of oxidation — a chemical reaction producing a new substance with different properties.
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5. Hydrochloric acid and sodium hydroxide reacting and forming salt and water → Chemical Change
*Explanation:* This is a neutralization reaction: HCl + NaOH → NaCl + H₂O. New substances (salt and water) are formed from the reactants — clear evidence of a chemical change.
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6. Digesting food into nutrients → Chemical Change
*Explanation:* Digestion involves breaking down complex molecules (like proteins, carbs, fats) into simpler ones (amino acids, glucose, fatty acids) through enzymatic reactions. These are chemical transformations.
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7. Melting ice into water → Physical Change
*Explanation:* Ice and liquid water are both H₂O — only the physical state changes (solid to liquid). No new substances are formed.
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8. Acid rain dripping onto limestone and making carbon dioxide gas → Chemical Change
*Explanation:* Limestone (calcium carbonate, CaCO₃) reacts with acid (e.g., H₂SO₄ or HNO₃) to produce CO₂ gas, water, and a salt. A new gas is released — this is a chemical reaction.
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9. Breaking a glass into pieces → Physical Change
*Explanation:* The glass is still made of the same material — only its shape and size have changed. No new substances are formed.
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10. Hydrogen peroxide decomposing into oxygen gas and water → Chemical Change
*Explanation:* Hydrogen peroxide (H₂O₂) breaks down into water (H₂O) and oxygen gas (O₂): 2H₂O₂ → 2H₂O + O₂. Since new substances are formed, this is a chemical change.
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✔ Final Answer Summary:
| # | Change Description | Type |
|---|----------------------------------------------------------|----------------|
| 1 | Heating water into steam | Physical |
| 2 | Milk going sour | Chemical |
| 3 | Dissolving sugar in water | Physical |
| 4 | Iron rusting | Chemical |
| 5 | HCl + NaOH → salt + water | Chemical |
| 6 | Digesting food into nutrients | Chemical |
| 7 | Melting ice into water | Physical |
| 8 | Acid rain on limestone → CO₂ | Chemical |
| 9 | Breaking a glass into pieces | Physical |
|10 | H₂O₂ → O₂ + H₂O | Chemical |
This distinction helps us understand whether matter’s identity is preserved (physical) or altered (chemical).
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1. Heating water into steam → Physical Change
*Explanation:* This is a change of state (liquid to gas). The water molecules (H₂O) remain chemically unchanged — no new substances are formed. Only the physical form and energy content change.
---
2. Milk going sour → Chemical Change
*Explanation:* Souring milk involves bacterial fermentation that converts lactose into lactic acid. This creates new chemical compounds and changes the taste, smell, and texture — indicating a chemical reaction has occurred.
---
3. Dissolving sugar in water → Physical Change
*Explanation:* Sugar molecules disperse among water molecules but do not react chemically. You can recover the sugar by evaporating the water, proving no new substance was formed.
---
4. Iron rusting → Chemical Change
*Explanation:* Rust is iron oxide (Fe₂O₃), formed when iron reacts with oxygen and water. This is a classic example of oxidation — a chemical reaction producing a new substance with different properties.
---
5. Hydrochloric acid and sodium hydroxide reacting and forming salt and water → Chemical Change
*Explanation:* This is a neutralization reaction: HCl + NaOH → NaCl + H₂O. New substances (salt and water) are formed from the reactants — clear evidence of a chemical change.
---
6. Digesting food into nutrients → Chemical Change
*Explanation:* Digestion involves breaking down complex molecules (like proteins, carbs, fats) into simpler ones (amino acids, glucose, fatty acids) through enzymatic reactions. These are chemical transformations.
---
7. Melting ice into water → Physical Change
*Explanation:* Ice and liquid water are both H₂O — only the physical state changes (solid to liquid). No new substances are formed.
---
8. Acid rain dripping onto limestone and making carbon dioxide gas → Chemical Change
*Explanation:* Limestone (calcium carbonate, CaCO₃) reacts with acid (e.g., H₂SO₄ or HNO₃) to produce CO₂ gas, water, and a salt. A new gas is released — this is a chemical reaction.
---
9. Breaking a glass into pieces → Physical Change
*Explanation:* The glass is still made of the same material — only its shape and size have changed. No new substances are formed.
---
10. Hydrogen peroxide decomposing into oxygen gas and water → Chemical Change
*Explanation:* Hydrogen peroxide (H₂O₂) breaks down into water (H₂O) and oxygen gas (O₂): 2H₂O₂ → 2H₂O + O₂. Since new substances are formed, this is a chemical change.
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✔ Final Answer Summary:
| # | Change Description | Type |
|---|----------------------------------------------------------|----------------|
| 1 | Heating water into steam | Physical |
| 2 | Milk going sour | Chemical |
| 3 | Dissolving sugar in water | Physical |
| 4 | Iron rusting | Chemical |
| 5 | HCl + NaOH → salt + water | Chemical |
| 6 | Digesting food into nutrients | Chemical |
| 7 | Melting ice into water | Physical |
| 8 | Acid rain on limestone → CO₂ | Chemical |
| 9 | Breaking a glass into pieces | Physical |
|10 | H₂O₂ → O₂ + H₂O | Chemical |
This distinction helps us understand whether matter’s identity is preserved (physical) or altered (chemical).
Parent Tip: Review the logic above to help your child master the concept of physical and chemical properties worksheet physical science a.
