CBSE Class 10 Chemistry Metals And Non Metals Worksheet Set 19

This printable CBSE Class 10 Science worksheet for Chapter 3, Metals and Non-metals, has 21 very short answer questions with answers. It covers ionic compounds, the reactivity series, occurrence of metals and corrosion.

Very Short Answer Questions

Question 1. Write the chemical equation for the reaction when a piece of zinc is placed in a solution of copper(II) sulphate.
Answer:
Zn + CuSO₄ → ZnSO₄ + Cu
In simple words: Zinc displaces copper.

Teacher's Note:
1. The blue colour fades.
2. Zinc is more reactive than copper.

Question 2. If P, Q, R, S, T represent metals in the decreasing order of their reactivity, which one is most likely to occur in the free state in nature?
Answer:
Metal T, because it is the least reactive.
In simple words: The least reactive metal is found free.

Teacher's Note:
1. The first in the list is the most reactive.
2. Gold is an example of such a metal.

Question 3. Why does copper not evolve hydrogen on reacting with dilute sulphuric acid?
Answer:
Copper is less reactive than hydrogen and lies below it in the reactivity series.
In simple words: Copper cannot displace hydrogen from acids.

Teacher's Note:
1. Metals above hydrogen can.
2. Silver and gold behave like copper.

Question 4. What are electrovalent compounds?
Answer:
Compounds formed by the transfer of electrons from a metal to a non-metal are called ionic or electrovalent compounds.
In simple words: They are made of oppositely charged ions.

Teacher's Note:
1. NaCl and MgCl₂ are examples.
2. The bond is called an ionic bond.

Question 5. Show the ion formation in (i) sodium and (ii) chlorine.
Answer:
(i) Na (2, 8, 1) → Na⁺ (2, 8) + e⁻
(ii) Cl (2, 8, 7) + e⁻ → Cl⁻ (2, 8, 8)
In simple words: Sodium loses one electron and chlorine gains one.

Teacher's Note:
1. Count the electrons in each shell before and after.
2. Both ions get the noble gas configuration.

Question 6. What can you say about the solubility of electrovalent compounds?
Answer:
They are generally soluble in water and insoluble in solvents such as kerosene and petrol.
In simple words: Ionic compounds dissolve in water.

Teacher's Note:
1. Water is a polar solvent.
2. Kerosene and petrol are non-polar.

Question 7. Why are ionic compounds hard crystalline solids?
Answer:
There is a strong force of attraction between the positive and negative ions, which holds them in a rigid crystal.
In simple words: Strong attraction between ions gives hardness.

Teacher's Note:
1. They are also brittle.
2. They have high melting points.

Question 8. Which metals are found in the free state in nature?
Answer:
The least reactive metals, at the bottom of the activity series, such as gold, silver and platinum.
In simple words: Unreactive metals are found free.

Teacher's Note:
1. Copper is sometimes also found free.
2. Free state is also called native state.

Question 9. Which metals are never found in the free state in nature?
Answer:
The most reactive metals at the top of the activity series: K, Na, Ca, Mg and Al.
In simple words: Very reactive metals always occur as compounds.

Teacher's Note:
1. They are extracted by electrolysis.
2. Sodium occurs as NaCl.

Question 10. How are metals classified on the basis of reactivity?
Answer:
They are grouped into three categories: (i) metals of low reactivity, (ii) metals of medium reactivity and (iii) metals of high reactivity.
In simple words: Low, medium and high reactivity.

Teacher's Note:
1. Each group has its own method of extraction.
2. Examples: Cu, Zn and Na.

Question 11. Which metals are found as oxides, sulphides etc. in the earth's crust?
Answer:
Metals of medium reactivity, such as zinc, iron and lead, found mainly as oxides, sulphides or carbonates.
In simple words: Medium reactive metals occur as compounds.

Teacher's Note:
1. They are extracted by reduction with carbon.
2. Ores are converted to oxides first.

Question 12. Write the equation when manganese dioxide is heated with aluminium powder.
Answer:
3MnO₂ + 4Al → 3Mn + 2Al₂O₃ + heat
In simple words: Aluminium reduces manganese dioxide.

Teacher's Note:
1. It is a displacement reaction.
2. It is used to obtain manganese.

Question 13. In the refining of silver, the recovery of silver from silver nitrate solution involves displacement by copper metal. Give the reason.
Answer:
Copper is more reactive than silver, so it displaces silver from silver nitrate solution.
In simple words: A more reactive metal displaces a less reactive metal.

Teacher's Note:
1. Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag.
2. The solution turns blue.

Question 14. What chemical process is used for obtaining a metal from its oxide?
Answer:
Reduction.
In simple words: Metal oxides are reduced to metals.

Teacher's Note:
1. Carbon, aluminium or electricity can be used.
2. Reduction is removal of oxygen.

Question 15. Which metals do not corrode easily?
Answer:
Gold, silver and platinum (the least reactive metals).
In simple words: They do not react with air and water.

Teacher's Note:
1. They are used in jewellery.
2. Copper corrodes slowly.

Question 16. Name one metal which corrodes when kept in the atmosphere.
Answer:
Iron (it rusts).
In simple words: Iron rusts in moist air.

Teacher's Note:
1. Silver tarnishes and copper turns green.
2. Rust is brown.

Question 17. Silver becomes blackish (tarnished) after some time. Why?
Answer:
A black layer of silver sulphide is formed on the surface by the action of sulphur compounds present in air.
In simple words: Silver reacts with sulphur gas in air.

Teacher's Note:
1. The layer can be cleaned with a polish.
2. Silver chloride also darkens in air.

Question 18. Why does a greenish layer appear on a copper vessel left in humid air for a few days?
Answer:
Copper reacts with moist carbon dioxide and oxygen of air to form a green coating of basic copper carbonate.
In simple words: Moist air makes copper turn green.

Teacher's Note:
1. The coating is CuCO₃.Cu(OH)₂.
2. Lemon juice removes it.

Question 19. A vessel made of a metal M acquires a blackish tinge on exposure to air after a few days. Name the metal M and the black substance.
Answer:
M is silver and the black substance is silver sulphide, Ag₂S.
In simple words: Silver forms a sulphide.

Teacher's Note:
1. Copper would turn green.
2. Gold does not tarnish.

Question 20. Give one example of a metal having a low melting point and a non-metal having a high melting point.
Answer:
Low melting point metal: gallium (or caesium). High melting point non-metal: diamond (carbon).
In simple words: Metals are not always high melting.

Teacher's Note:
1. Gallium melts in the palm.
2. Diamond melts above 3500 °C.

Question 21. Give one example of a metal which is a poor conductor of electricity and a non-metal which is a good conductor.
Answer:
Poor conductor metal: lead (or mercury). Good conductor non-metal: graphite.
In simple words: Lead conducts poorly; graphite conducts well.

Teacher's Note:
1. Graphite has free electrons.
2. Most non-metals are insulators.