Short Answer Questions
Question 1: Which reaction takes place during rust formation?
Answer: Iron reacts with oxygen and moisture to form iron oxide. Iron oxide is brown in colour and is commonly known as rust.
Fe + O2 + H2O → Fe2O3
Question 2: Copper coins develop greenish patches when kept unused for a long time. Why?
Answer: When copper is exposed to moist air for a long time, it acquires a greenish coating. The green coat is a mixture of copper hydroxide and copper carbonate.
2Cu + H2O + CO2 + O2 → Cu(OH)2 + CuCO3
Due to this, copper coins develop greenish patches when kept unused for a long time.
Question 3: How does a base react with metals and non-metals?
Answer: Reaction of base with metals and non-metals is as follows:
- Metals react with sodium hydroxide to produce hydrogen gas.
- Non-metals' reaction with sodium hydroxide is much complex.
Question 4: What happens when zinc granules are kept in copper sulphate solution?
Answer: When zinc granules are kept in copper sulphate solution, the blue colour of copper sulphate disappears and the solution becomes colourless. Zinc is more reactive than copper and hence displaces copper from copper sulphate solution and forms zinc sulphate.
CuSO4 + Zn → ZnSO4 + Cu
Question 5: What happens when copper turnings are kept in zinc sulphate solution? Give reason for your answer.
Answer: Copper is less reactive than zinc. Hence, copper cannot displace zinc from a compound. Hence, no reaction takes place when copper turnings are kept in zinc sulphate solution.
Question 6: How do metals react with acids?
Answer: Metals generally react with acids and produce hydrogen gas. Confirmation of hydrogen gas is done by bringing a burning matchstick or a burning candle near the gas. When the burning matchstick or candle burns with a pop sound it confirms the evolution of hydrogen gas. But copper does not react with dilute sulpuric acid.
Question 7: Write a brief note about physical state of metals.
Answer: Most of the non-metals are available as solid at room temperature. But mercury is present as liquid at room temperature.
Long Answer Type Questions
Question 1: Differentiate between metals and non-metals on the basis of malleability, ductility and conductivity.
|Metals are malleable, i.e. they can be beaten into thin sheets.
|Non-metals are not malleable.
|Metals are ductile, i.e. they can be drawn into thin wires.
|Non-metals are not ductile.
|Metals are good conductors of heat and electricity.
|Non-metals are bad conductors of heat and electricity. (exception: graphite)
Question 2: Differentiate between metals and non-metals on the basis of luster, sonority and physical state.
|Metals are sonorous, i.e. they produce a typical metallic sound when hit with something.
|Non-metals are not sonorous.
|Metals have metallic shine; called lustre.
|Non-metals are usually dull. (exceptions: diamond and graphite)
|Most of the non-metals are available as solid at room temperature; except mercury. Sodium and potassium are so soft that they can be cut with knife.
|Non-metals are available in all the three states of matter.
Question 3: How do metals and non-metals react with water?
Answer: Some metals react vigorously with water, while some others do not react at all with water.
Example: Sodium is a highly reactive metal and reacts vigorously with water. This is a highly exothermic reaction. During this reaction; sodium catches fire because of too much heat being evolved. Due to this, sodium is stored in kerosene to prevent accidental fire.
- Iron reacts slowly with water.
- Copper does not react with either cold or hot water, but reacts with steam.
- Silver and gold do not react with water at any temperature.
Usually, non-metals do not react with water, but some non-metals react vigorously with air. Such non-metals are stored in water to prevent their reaction with air. For example; phosphorus is stored in water to prevent its reaction with air.
Question 4: List some uses of metals.
Answer: Uses of metals:
- Metals are used for making machines and tools.
- Iron is used for making ships, bridges, railway lines, etc.
- Copper is used for making electric wires.
- Aluminium is used for making utensils.
- Gold and silver are used for making ornaments.
Question 5: List some uses of non-metals.
Answer: Uses of non-metals:
- Oxygen is used by all living beings for respiration.
- Carbon dioxide is used by plants for photosynthesis.
- Chlorine is used for water purification.
- Iodine solution is used as antiseptic and applied on wounds.
- Coal (carbon) is an important fuel.