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Olympiad (Class 7) Physical and chemical changes — practice questions — page 2

Explore 46 free Physical and chemical changes questions in Olympiad (Class 7) Science. Open each question or exercise to read its content, reference answers and available explanation.

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Physical and chemical changes questions and exercises with answers

Showing questions 31–46 of 46.

When iron rusts, the rust takes up more space than the iron. This can causeRead the answer and worked solution →A thin layer of rust on iron does not protect the metal below because rustRead the answer and worked solution →Coating iron with a zinc layer to stop rusting is calledRead the answer and worked solution →Zinc keeps protecting a galvanized scratch because zinc isRead the answer and worked solution →Galvanization is named after the Italian scientistRead the answer and worked solution →Which of these will protect an iron railing from rusting?Read the answer and worked solution →Silica gel packets are placed in boxes of machines shipped by sea. They help prevent rust byRead the answer and worked solution →A thin layer of grease on iron tools stored for long keeps them from rusting byRead the answer and worked solution →Stainless steel resists rusting because it forms a thin layer ofRead the answer and worked solution →Rusting is specifically the corrosion of which metal?Read the answer and worked solution →A chemical reaction changes the atoms of a substance byRead the answer and worked solution →Which of these is a physical change?Read the answer and worked solution →Baking soda is added to vinegar and bubbles of gas appear. This showsRead the answer and worked solution →Which pair correctly matches the change with its type?Read the answer and worked solution →Copper turns green after long exposure to damp air. This shows copper hasRead the answer and worked solution →A change in colour during a process most reliably suggestsRead the answer and worked solution →

Worked practice questions

When iron rusts, the rust takes up more space than the iron. This can cause

  1. structures to be damaged
  2. iron to become lighter
  3. water to freeze in it
  4. magnets to form in it
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Correct answer: A. structures to be damaged

The expanding oxide pushes with great force and damages iron structures.

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A thin layer of rust on iron does not protect the metal below because rust

  1. lets air and water in
  2. is harder than steel
  3. repels all moisture
  4. is a metal coating
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Correct answer: A. lets air and water in

Air and water pass through rust, so the iron beneath keeps corroding.

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Coating iron with a zinc layer to stop rusting is called

  1. sublimation
  2. galvanization
  3. evaporation
  4. fermentation
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Correct answer: B. galvanization

Galvanization is the process of applying a protective zinc coating to iron or steel.

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