VSAQ for Chapter 5 Changes Around Us: Physical and Chemical Class 7 Science NCERT
Important Questions1
Q1: Is cooking food a desirable change?
Answer
Yes, it is a beneficial change.
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2
Q2: What is added to steel to make it stainless?
Answer
Stainless steel is made by mixing iron with carbon and metals like chromium, nickel, and manganese.
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3
Q3: Can physical changes be reversed?
Answer
Yes, like freezing water.
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4
Q4: What is a chemical change?
Answer
A change, in which a new substance with different properties is formed, is known as a chemical change.
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5
Q5: A change, in which a new substance with different properties is formed, is known as a _________________
Answer
Chemical change
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6
Q6: What is the fire triangle?
Answer
The three requirements for combustion: fuel, oxygen, and heat.
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7
Q7: What is erosion?
Answer
The movement of rocks, soil, or sediments by wind or water.
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8
Q8: State the two important conditions for rusting.
Answer
Presence of water and presence of oxygen
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9
Q9: What is weathering?
Answer
The breakdown of rocks into smaller pieces through physical or chemical processes.
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10
Q10: What is the ignition temperature?
Answer
The minimum temperature at which a substance catches fire.
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11
Q11: What is melting?
Answer
Melting is the process of turning a solid to a liquid.
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12
Q12: Name the process by which water molecules continuously change to vapour.
Answer
Evaporation
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13
Q13: What is an irreversible change?
Answer
A change that cannot be undone, like burning wood.
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14
Q14: What is bioluminescence?
Answer
Light produced by living organisms, like fireflies, through a chemical change.
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15
Q15: A medicine is the end product of the chain of ____________
Answer
Chemical reaction
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16
Q16: Condensation of steam is a chemical process or physical change?
Answer
Physical change
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17
Q17: Cutting of log of wood into pieces is a chemical process or physical change?
Answer
Physical change
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18
Q18: Name the two methods by which rusting of iron can be prevented.
Answer
By painting or greasing and by galvanizing with Zinc
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