Day 3: Physical vs. Chemical Changes | Middle Stage Science | Apex Institute of Maths and Sciences

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Day 3: Physical vs. Chemical Changes | Middle Stage Science | Apex Institute of Maths and Sciences

Day 3: Physical vs. Chemical Changes ⚗️

Middle Stage Science | Apex Institute of Maths and Sciences

🎯 1. Concept: Identifying the Change

Matter is constantly changing. Scientists classify these changes into two main types based on whether a new substance is formed.

  • Physical Change: Only the physical properties (like shape, size, or state) change. No new substance is created. These are often reversible. (Example: Ice melting into water).
  • Chemical Change: Atoms are rearranged to form new substances with different properties. These are usually irreversible. (Example: Paper burning into ash).

💡 2. Signs of a Chemical Reaction

How do we know a chemical change has happened? Look for these clues:

  • Gas Production: Seeing bubbles or smelling a new odor.
  • Temperature Change: The substance gets hot or cold without outside help.
  • Color Change: A permanent change in color (like rust forming on a nail).
  • Precipitate: A solid forming when two liquids are mixed.

🌍 3. Science in Our Daily Life

Cooking an Egg: When you fry an egg, the heat causes the proteins to change forever. You cannot turn a fried egg back into a raw one. This is a Chemical Change.

Dissolving Sugar: When you stir sugar into water, it “disappears,” but it is still sugar. You can get it back by evaporating the water. This is a Physical Change.

📝 4. Home Observation Task

Task: Observe a rusted iron object and a piece of crumpled paper. Identify which one underwent a chemical change and which one a physical change. List the “clues” that helped you decide.

✅ 5. Day 3 Research Assessment

Analyze each scenario using the concepts provided above.

Easy
1. Which change results in a completely new substance being formed?
Solution: A chemical change rearranges atoms to create something new (Part 1).
Easy
2. Breaking a glass bottle is an example of a:
Solution: Only the shape and size changed; it is still glass (Part 1).
Easy
3. Most physical changes are ________.
Solution: Physical changes, like melting ice, can usually be undone (Part 1).
Easy
4. Which of these is a sign of a chemical reaction?
Solution: Seeing bubbles indicates gas is being produced (Part 2).
Medium
5. Why is boiling water considered a physical change?
Solution: Steam is still water (H2O); only the state changed (Part 1).
Medium
6. Rusting of an iron nail is a chemical change because:
Solution: Permanent color change (rust) is a clue for a chemical reaction (Part 2).
Medium
7. When you stir salt into water, you are creating a:
Solution: Dissolving is reversible and no new substance is made (Part 3).
Medium
8. If two liquids mix and a solid (precipitate) forms, what happened?
Solution: Formation of a precipitate is a chemical clue (Part 2).
Hard
9. Assertion: Digestion of food is a chemical change.
Reason: Enzymes break down food into new substances that the body can use.
Solution: Digestion creates new nutrients that cannot be turned back into food.
Hard
10. Why is a candle burning both a physical and a chemical change?
Solution: Melting is a change of state (Physical), but burning creates light and ash (Chemical).
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