Rusting and Crystallization MCQs
Rusting and Crystallization – MCQs with Answers & Explanations
Class: 7 | Subject: Science | Section: Physical & Chemical Changes | Topic: Rusting and Crystallization MCQs
Based Strictly on NCERT Syllabus | CBSE Board Examination Pattern
Based Strictly on NCERT Syllabus | CBSE Board Examination Pattern
1. Rusting is a process that affects:
Answer: B. Iron
Rusting specifically refers to corrosion of iron forming iron oxide.
Rusting specifically refers to corrosion of iron forming iron oxide.
2. Rust is chemically known as:
Answer: B. Rust is hydrated iron(III) oxide.
3. Rusting requires:
Answer: C. Both oxygen and water are essential.
4. Rusting is a:
Answer: B. New substance (rust) forms.
5. Galvanization prevents rusting by coating iron with:
Answer: B. Zinc protects iron from air and moisture.
6. Painting iron objects prevents rusting because it:
Answer: B. Paint forms a protective barrier.
7. Oiling machine parts prevents rusting by:
Answer: C. Oil blocks moisture and oxygen.
8. Stainless steel does not rust because it contains:
Answer: B. Chromium forms protective layer.
9. Crystallization is a process of:
Answer: B. It purifies solids in crystal form.
10. Alum crystals are prepared by:
Answer: B. Saturated solution forms crystals on cooling.
11. Crystallization is a:
Answer: B. No new substance forms.
12. Pure crystals are formed from:
Answer: B. Saturated solutions deposit crystals.
13. Copper sulphate crystals are:
Answer: B. They form bright blue crystals.
14. Rusting can be slowed by:
Answer: C. Paint blocks air contact.
15. Which condition increases rusting?
Answer: B. Moisture accelerates rusting.
16. Crystallization helps in:
Answer: B. Impurities remain in solution.
17. Rusting is an example of:
Answer: A. It is corrosion of iron.
18. Which metal does not rust?
Answer: C. Aluminium forms protective oxide layer.
19. Crystals are usually:
Answer: C. They have definite shape and purity.
20. Best method to obtain large pure crystals:
Answer: B. Slow cooling allows proper crystal growth.