Q1. Give examples of five elements that are metallic.
Ans. Copper, iron, gold, silver and aluminium.
Q2. Give examples of five elements that are non-metallic.
Ans. Sulphur, phosphorus, carbon, hydrogen, oxygen, chlorine and bromine.
Q3. How do metals and non-metals combine?
Ans. Metals and non-metals combine by transference of electrons from metals to non-metals.
Q4. What is an ionic bond ?
Ans: The electrostatic attraction between the cation and anion is called the ionic bond.
Q5. Hydrogen is not a metal, yet it is placed in the activity series of metals. why ?
Ans. Like metals, hydrogen can lose an electron to form positive ion (H+).
Q6. Why is H2 gas not evolved when a metal is treated with nitric acid.
Ans. Nitric acid is a strong oxidising agent. It oxidises the H2 produced to water and itself gets reduced to some oxide of nitrogen, i.e. nitrous oxide (N2O), nitric oxide (NO).
Q7. Name two metals other than silver and gold which are not attacked even by steam.
Ans. Lead and copper.
Q8. What are minerals ?
Ans. The elementary state or the compounds in form of which the metals occur in nature, associated with impurities of gangue, etc. are called minerals.
Q9. What is an ‘ore’ ?
Ans. The mineral from which metal can be extracted conveniently and economically is called an ore.
Q10. What do you understand by ‘thermite reaction’ ?
Ans. The reduction of metal oxide to metal using aluminium as the reducing agent is called thermite reaction or aluminothermy.
Q11. Why aluminium does not occur in native state ?
Ans. Aluminium, being a reactive metal, combines with oxygen readily to form alumina.
Q12. What is the composition of stainless steel ?
Ans. Iron (74%), chromium (18%) and nickel (8%).
Q13. Name the metals which are usually alloyed with gold to make it harder.
Ans. Copper and silver.
Q14. What is meant by 22 carat gold ?
Ans. An alloy consisting of 22 parts by weight of pure gold and 2 parts by weight of copper or silver is called 22 carat gold.
Q15. Why is pure gold not suitable for making ornaments ?
Ans. Because, pure gold is soft and ductile.
Q16. Name a metal which is used for galvanising iron ?
Q17. Why is an iron grill painted frequently ?
Ans. To protect it from rusting.
Q18. Name two metals which are highly resistant to corrosion.
Ans. Platinum and gold.
Q19. The corrosion of iron is called… .
Q20. The process of depositing a thin layer of zinc on iron articles is called …….. .
Q21. State conditions for rusting of iron.
Ans. Presence of moisture and air.
Q22. Metals generally occur in solid state. Name and write the symbol of a metal that exists in liquid state at room temperature.
Ans. Mercury (Hg).
Q23. Alloy are used in electrical heating devices rather than pure metals. Give one reason.
Ans. Alloys generally have lower melting points than the constituent metals. Therefore, in case short – circuiting occurs, the alloy melts, electrical connection is broken and fire are avoided.