Gide Questions-see activity cards1.What have you observed from the burning candle when it isuncovered and covered?2. What helped the candle continue burning? Explain your answer3. What changes took place in the candle?4. What happened to the sliced apple exposed to the air andsoaked in water?5. What changes took place in both of the halves of the slicedapple?6. What physical change(s) occurred?7. What chemical change(s) occurred?8. What condition contributed to these changes?9. Have you observed rusting of iron window grills, why do youthink this change occur?10. To what elements are iron window grills exposed to?11. What do you think are the reasons of rusting?
Answer (1)
Burning candle 1. uncovered: The candle burns brightly, producing a flame, heat, and smoke. Covered: The flame will eventually extinguish because it runs out of oxygen.2. Oxygen: Oxygen is essential for combustion (burning). The candle needs oxygen to react and produce the flame. When covered, the oxygen supply is cut off.3. Changes: The candle wax melts, then burns, turning into soot and gases. The wick also burns away.Sliced Apple4. Exposed to Air: The apple will brown due to oxidation. The exposed flesh reacts with oxygen in the air. Soaked in Water: The apple will soften and may become discolored. Water can cause the apple to break down.5. Changes: Both halves will undergo changes, but the exposed half will brown more quickly due to oxidation. The soaked half will soften and may become discolored.Physical and Chemical Changes6. Physical Changes: Melting of wax, softening of the apple, changes in shape and size. These changes are reversible (you can re-solidify wax, but not easily reverse the apple’s changes).7. Chemical Changes: Burning of the candle (wax turning into soot and gases), browning of the apple (oxidation). These changes are irreversible.8. Conditions: The presence of oxygen is crucial for both burning and oxidation.Rusting9. Rusting: Iron window grills rust because they are exposed to oxygen and moisture (water).10. Elements: Iron grills are exposed to oxygen, water (rain, humidity), and sometimes even salt (from the air or road spray).11. Reasons: Rusting is a chemical reaction called oxidation. Iron reacts with oxygen and water to form iron oxide (rust).Key ConceptsPhysical Change: A change in the form or appearance of a substance, but not its chemical composition.Chemical Change: A change that results in the formation of new substances with different properties.Oxidation: A chemical reaction where a substance combines with oxygen.
