Science Class- 10
Class 10 - Chapter 3: Metals and Non-Metals
Q1. Which of the following pairs will give displacement reactions?
Answer: (d) AgNO3 solution and copper metal.
Copper is more reactive than silver. Therefore, copper displaces silver from silver nitrate solution.
Chemical Equation:
Cu + 2AgNO3 → Cu(NO3)2 + 2Ag
Q2. Which of the following methods is suitable for preventing an iron frying pan from rusting?
Answer: (c) Applying a coating of zinc.
Grease and paint cannot be used on a frying pan because they burn during heating. Zinc coating prevents rusting by protecting iron from air and moisture.
Q3. An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be
Answer: (a) Calcium.
Calcium reacts with oxygen to form calcium oxide, an ionic compound with a high melting point. It reacts with water to form calcium hydroxide.
Q4. Food cans are coated with tin and not with zinc because
Answer: (c) Zinc is more reactive than tin.
Zinc may react with acids present in food and produce harmful substances. Tin is less reactive and safer for coating food cans.
Q5(a). How would you use a hammer, a battery, a bulb, wires and a switch to distinguish between metals and non-metals?
Hammer Test:
- Metals are malleable and do not break when hammered.
- Non-metals are brittle and break into pieces.
Electrical Conductivity Test:
- Connect the sample in an electric circuit using a battery, bulb, wires and a switch.
- If the bulb glows, the sample is a metal.
- If the bulb does not glow, the sample is a non-metal.
Q5(b). Assess the usefulness of these tests in distinguishing between metals and non-metals.
These tests are generally useful because metals are malleable and good conductors of electricity, whereas non-metals are brittle and poor conductors.
However, there are exceptions. For example, graphite is a non-metal but conducts electricity. Therefore, more than one test should be used.
Q6. What are amphoteric oxides? Give two examples of amphoteric oxides.
Amphoteric oxides are oxides that react with both acids and bases to form salt and water.
Examples:
- Aluminium oxide (Al2O3)
- Zinc oxide (ZnO)
Q7. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
| Metals that displace hydrogen | Metals that do not displace hydrogen |
|---|---|
| Zinc (Zn) | Copper (Cu) |
| Magnesium (Mg) | Silver (Ag) |
Q8. In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?
| Component | Material Used |
|---|---|
| Anode | Impure metal M |
| Cathode | Thin strip of pure metal M |
| Electrolyte | Solution of a salt of metal M |
Q9(a). What will be the action of the gas on:
(i) Dry litmus paper: No change.
(ii) Moist litmus paper: Blue litmus turns red.
Reason: The gas evolved is sulphur dioxide (SO2), which forms sulphurous acid in the presence of water.
Q9(b). Write a balanced chemical equation for the reaction taking place.
S + O2 → SO2
Q10. State two ways to prevent the rusting of iron.
- Painting the iron surface.
- Galvanisation (coating iron with zinc).
Q11. What type of oxides are formed when non-metals combine with oxygen?
Non-metals generally form acidic oxides when they react with oxygen.
Example: CO2, SO2.
Q12(a). Platinum, gold and silver are used to make jewellery.
These metals are lustrous, malleable, ductile and highly resistant to corrosion. Therefore, they are suitable for making jewellery.
Q12(b). Sodium, potassium and lithium are stored under oil.
These metals are highly reactive and react vigorously with oxygen and moisture in air. Storing them under oil prevents such reactions.
Q12(c). Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
Aluminium forms a thin protective layer of aluminium oxide on its surface which prevents further corrosion. It is also a good conductor of heat and lightweight.
Q12(d). Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
Metal oxides are easier to reduce to metals than carbonate and sulphide ores. Hence, these ores are first converted into oxides.
Q13. Tarnished copper vessels are cleaned with lemon or tamarind juice. Explain why.
Copper vessels develop a green coating of copper oxide or basic copper carbonate.
Lemon and tamarind contain acids which react with this coating and dissolve it, thereby cleaning the vessels.
Q14. Differentiate between metals and non-metals on the basis of their chemical properties.
| Metals | Non-metals |
|---|---|
| Form basic or amphoteric oxides. | Form acidic or neutral oxides. |
| React with dilute acids to liberate hydrogen gas. | Generally do not react with dilute acids. |
| Lose electrons and form positive ions. | Gain electrons and form negative ions. |
| Usually form ionic compounds. | Usually form covalent compounds. |
Q15. Can you identify the nature of the solution used by the goldsmith?
The goldsmith most likely used aqua regia.
Aqua regia is a mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio 3:1.
It dissolves a small amount of gold from the ornaments, reducing their weight while making them appear shiny.
Q16. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).
Copper is used because:
- It is a good conductor of heat.
- It does not react with hot water or steam.
- It is corrosion resistant.
Steel contains iron, which can react with steam and may corrode. Therefore, copper is preferred.