CBSE Science Class 7
Physical and Chemical Changes
Physical and Chemical Changess - Chapter Wise CBSE Solved Question and Answer Based On NCERT
Very Short Q&A:
Q1: What is rust?
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Ans:
When iron oxide is hydrated, it is known as Rust(Fe2O3. XH2O)
Q2: What type of change in rust?
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Q3: What type of change is photosynthesis?
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Q4: What is a chemical change?
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Ans:
A change, in which a new substance with different properties is formed, is known as a chemical change.
Q5: A change, in which a new substance with different properties is formed, is known as a _________________.
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Q6: ___________is a property by virtue of which a metal can be beaten into thin sheets without breaking.
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Q7: Write the chemical formula of blue vitriol.
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Ans:
Crystals of copper sulphate pent hydrate (CuSO4.5H2O) are blue in colour. So, it is commonly known as blue vitriol.
Q8: State the two important conditions for rusting.
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Ans:
Presence of water and presence of oxygen
Q9: What is freezing point of water?
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Ans:
The freezing point is 0 °C at which water freezes.
Q10: What is freezing of water?
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Ans:
Freezing is the process in which water turns to ice when cold enough (below 0 °C temperature).
Q11: What is melting?
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Ans:
Melting is the process of turning a solid to a liquid.
Q12: Name the process by which water molecules continuously change to vapour.
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Q13: At what temperature water evaporates?
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Q14: What is the boiling point of water?
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Q15: In physical change a new substance is formed. True/False.
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Q16: Extraction of metal is a chemical process or physical process?
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Q17: A medicine is the end product of the chain of ________________________.
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Q18: Sound may be produced during a chemical reaction yes or no?
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Q19: During a chemical reaction
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Q20: Heat, light or any other radiation like UV rays may be given off or absorbed during a physical change True/False.
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Q21: Iron pipes coated with zinc do not get rusted easily. True/False.
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Q22: Condensation of steam is chemical process or physical change?
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Q23: Cutting of log of wood into pieces is a chemical process or physical change?
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Q24: Name the two methods by which rusting of iron can be prevented.
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Ans:
By painting or greasing and by galvanizing with chromium or zinc
Q25: Setting of curd is a _______________ process.
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Q26: Give an example of chemical change in which heat, light, sound and unpleasant gases are produced.
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Ans:
Explosion of a firework
Q27: Digestion is a __________________ change.
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Q28: Spoiling of food is a ____________________ change.
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Q29: Which of the two is permanent change chemical change or physical change?
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Q30: Define galvanisation.
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Ans:
The process of depositing a layer of zinc on iron is called galvanisation.
Q31: Name the metals involved in making stainless steel.
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Ans:
Chromium, nickel and manganese.
Q32: What kind of change involved in burning of coal?
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Q33: Formation of manure from leave is a physical change. True/False
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Q34: Write down the equation representing the process of rusting.
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Ans:
Iron(Fe) + oxygen (O2)->water (H2O) + rust (iron oxide Fe2O3)
