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Chapter: 02. Physical And Chemical Changes

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SECTION A: OBJECTIVE TYPE QUESTIONS

1. Multiple Choice Questions (MCQs)

Choose the correct option for each of the following questions:
Which of the following is an endothermic change?
(a) Burning of fuel
(b) Dissolving glucose in water
(​c​) Rusting of iron
(d) Curdling of milk
When zinc granules react with dilute hydrochloric acid, which gas is evolved?
(a) Oxygen
(b) Carbon dioxide
(​c​) Hydrogen
(d) Nitrogen
Which of the following changes can be considered both desirable and undesirable depending on the context?
(a) Curdling of milk
(b) Cutting down of trees
(​c​) Occurrence of landslides
(d) Ageing of humans
When a magnet is brought near a strongly heated and cooled mixture of iron filings and sulphur powder, what happens?
(a) Only sulphur is attracted to the magnet
(b) Only iron filings are attracted to the magnet
(​c​) Both elements are attracted to the magnet
(d) Neither substance is attracted to the magnet
Which of the following is a periodic change?
(a) Swinging of a clock pendulum
(b) Coughing
(​c​) Eruption of a volcano
(d) Occurrence of thunder and lightning
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2. Fill in the Blanks

Fill in the blanks with the most appropriate word(s). Use ‘_ _ _ _ _ _ _ _ _ _ _ _ _ _’ for the blanks.
The process of change of gas directly into solid on cooling is called _ _ _ _ _ _ _ _ _ _ _ _ _ _.
In _ _ _ _ _ _ _ _ _ _ _ _ _ _ changes, heat energy is absorbed from the surroundings.
The reddish-brown coating formed on an iron nail kept in water is called _ _ _ _ _ _ _ _ _ _ _ _ _ _.
When we strongly heat sugar, it melts and eventually turns into a black residue called _ _ _ _ _ _ _ _ _ _ _ _ _ _.
Evaporation takes place slowly and only from the _ _ _ _ _ _ _ _ _ _ _ _ _ _ of the liquid.
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3. True or False Questions

State whether the following statements are True or False:
Photosynthesis is a physical change because plants absorb solar energy.
Boiling of water is a reversible change.
Spoilage of food is a desirable change because it occurs naturally.
During a chemical change, both the physical and chemical properties of the substance change.
Dissolving quicklime in water is an endothermic change because it makes the beaker cold.
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4. Complete the Series

Analyze the relationship in the first pair and complete the second pair:
Melting of ice : Reversible change :: Burning of paper : _ _ _ _ _ _ _ _ _ _ _ _ _ _
Sunset and sunrise : Periodic change :: Landslide : _ _ _ _ _ _ _ _ _ _ _ _ _ _
Melting of wax : Physical change :: Burning of a candle wick : _ _ _ _ _ _ _ _ _ _ _ _ _ _
Dissolving ammonium chloride in water : Endothermic change :: Dissolving quicklime in water : _ _ _ _ _ _ _ _ _ _ _ _ _ _
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SECTION B: DEFINITIONS & DIFFERENCES

5. Explanation of Terms

Explain the following terms in one or two sentences:
Sublimation
Chemical Change
Periodic Change
Evaporation
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6. Identify and/or Differentiate Concepts

Differentiate between Evaporation and Boiling based on the following parameters:
Speed of the process
Part of the liquid where it occurs
Effect on temperature (cooling)
Compare Physical Change and Chemical Change by completing the table below:
Parameter
Physical Change
Chemical Change
Formation of new substances
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Reversibility
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Change in chemical composition
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SECTION C: SHORT ANSWER & PRACTICAL/OBSERVATION QUESTIONS

7. Short Answer Questions

Answer the following questions briefly:
Why does an apple slice turn brown when kept in the open air for some time?
Give one example of a change that is human-made, irreversible, fast, and chemical.
Why is the growth of a seedling into a tree classified as a slow and irreversible change?
What is the test to confirm the evolution of hydrogen gas when zinc granules react with dilute hydrochloric acid?
Explain why putting a few drops of spirit on your palm makes it feel cold.
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8. Diagram-Based Question

The diagram shows an experimental setup where ammonium chloride is heated in a china dish covered by an inverted funnel.
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What scientific process is demonstrated in the diagram? Define this process.
Is the change taking place inside the funnel temporary and reversible, or permanent and irreversible? Why?
How can we recover the solid ammonium chloride after the heating is stopped?
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9. Environmental Awareness & Everyday Use

Rainfall is a natural change. Explain how rainfall can be a desirable change for a farmer at one time, but an undesirable change for the same farmer at another time.
Many useful metals like iron, copper, and aluminium are extracted using chemical methods. Why are these chemical extraction processes considered highly important for human society?
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SECTION D: LONG ANSWER QUESTIONS

10. Long Answer Questions

Answer the following questions in detail:
The Iron and Sulphur Experiment:
(a) What happens when iron filings and sulphur powder are mixed together without heating? Describe the observation when a magnet is brought near this mixture.
(b) What happens when this mixture is strongly heated in a china dish until it melts and turns dark grey? Describe the observation when a magnet is brought near the heated product.
(​c​) Classify both processes (simple mixing vs. heating) as physical or chemical changes and give reasons to justify your classification.
The Burning Candle:
Explain how the burning of a candle represents a simultaneous physical and chemical change. Describe the physical change part and the chemical change part clearly, explaining what happens to the wax in each.
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