Materials: Metals and Non-metals
Materials: Metals and Non-metals - NCERT Guide Science Class 8
Q1: Which of the following can be beaten into sheets?
- Zinc
- Phosphorous
- Sulphur
- Oxygen
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Q2: Which of the following statements is correct?
- All metals are ductile.
- All non-metals are ductile.
- Generally metals are ductile.
- Some non-metals are ductile
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Q3: Which of the following statements is correct?
- Phosphorous are very __________ non-metal.
- Metals are ________ conductor of heat and _____________.
- Iron is _________ reactive than copper.
- Metals react with acids to produce _______________ gas.
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Ans:
(a) reactive (b) good, electricity (c) more (d) hydrogen
Q4: Mark ‘T’ if the statement is true and ‘F’ if it is false:
- Generally non-metals react with acids.
- Sodium is a very reactive metal.
- Copper displaces zinc from zinc sulphate solution.
- Carbon can be drawn into wires.
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Ans:
(a) F (b) T (c) F (d) F
Q5: Some properties are listed in the following table. Distinguish between metals and non-metals on the basis of their properties.
- Appearance
- Hardness
- Malleability
- Ductility
- Heat conduction
- Conduction of electricity
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Ans:
| Properties |
Metals |
Non-Metals |
- Appearance
- Hardness
- Malleability
- Ductility
- Heat conduction
- Conduction of electricity
|
- Lustrous
- Hard except sodium and potassium.
- Generally Malleable.
- Generally ductile
- Good conductors
- Good conductors
|
- Non-lustrous
- Generally soft except diamond
- Non-malleable
- Non-ductile.
- Poor conductors
- Poor conductors
|
Q6: Give reasons for the following:
- Aluminium foils are used to wrap food items.
- Immersion rods are made up of metallic substances.
- Copper can not displace zinc from its salt-solution.
- Sodium and Potassium are stored in Kerosene.
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Ans:
- Aluminium foils are used to wrap food items because aluminium being a soft malleable metal it can be beaten to in sheets to form thin wrapping sheets. Moreover it does not react with food items.
- Immersion rods are made of metallic substances metals are good conductors of heat and electricity. They get hot very soon when electric current is passed through them and thus warm the water.
- Copper can not displace zinc from its salt-solution because copper is less reactive than zinc. A less reactive metal can not displace more reactive metal from its solution.
- Sodium and Potassium are stored in Kerosene since they are very reactive. They quickly react in air and water.
Q7: Can you store acidic lemon pickles in an aluminium utensil? Explain.
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Ans:
No, we can not store acidic lemon pickles in aluminium utensils because aluminium is a metal. Metals readily react with acids to produce hydrogen gas. So, if the aluminium metal comes in contact with acidic lemon pickles, it will react to release hydrogen, which would spoil the food and render it unsuitable to consume.
Q8: In the following table some substances are given in column I. In column II some uses are given. Match the items in Column I with those in Column II.
| column I |
column II |
- Gold
- Iron
- Aluminium
- Carbon
- Copper
- Mercury
|
- Thermometers
- Electric wire
- Wrapping food
- Jewellary
- Machinery
- Fuel
|
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Ans:
1-d 2-e 3-c 4-f 5-b 6-a
Q9: What happens when:
- Dilute sulphuric acid is poured on a copper plate?
- Iron nails are placed in copper sulphate solution?
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Ans:
- When dilute sulphuric acid is poured on a copper plate it reacts with copper to form copper sulphate and hydrogen. As a result the copper gets eroded which takes place according to the following equation:
Sulphuric acid + Copper --> Copper sulphate + Hydrogen.
- When iron nails are placed in copper sulphate solution the iron being more reactive will replace copper from its solution to form ferrous sulphate (iron sulphate) and thesolution will turn light green.
Iron + Copper sulphate --> Iron sulphate + Copper.
Q10: Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
- How will she find the nature of the gas?
- Write down equations of all the reactions taking place in this process.
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Ans:
- To check the nature of the gas first she has to dissolve the gas in water. Then she has to test this gaseous solution with litmus paper. If red litmus turns blue, then it is basic in nature and if blue litmus turns red then it is acidic in nature.
- (a) Carbon dioxide + Water --> Carbolic acid
(b) Sulphur dioxide + Water --> Sulphurous acid.
