NCERT Class 8 Science Chapter 4 Solution
Brief Information: This post contains the solution for Chapter 4 Crop Production and Management of Class 8 of the CBSE and also Gujarat Board (GSEB) books by GCERT (based on new NCERT).
Q1. Which of the following can be beaten into thin sheets?
Question 1.
Which of the following can be beaten into thin sheets?
(a) Zinc
(b) Phosphorus
(c) Sulphur
(d) Oxygen
Ans.
(a) Zinc
Q.2 Which of the following statements is correct?
(a) All metals are ductile.
(b) All non-metals are ductile.
(c) Generally, metals are ductile.
(d) Some non-metals are ductile.
Ans.
(c) Generally, metals are ductile
Q.3. Fill in the blanks.
(a) Phosphorus is a very reactive non-metal.
(b) Metals are good conductors of heat and electricity.
(c) Iron is more reactive than copper.
(d) Metals react with acids to produce hydrogen gas.
Q.4. Mark ‘T’ if the statement is true and ‘F’ if it is false.
(a) Generally, non-metals react with acids. – F (False)
(b) Sodium is a very reactive metal. – T (True)
(c) Copper displaces zinc from zinc sulphate solution. – F (False)
(d) Coal can be drawn into wires. – F (False)
Q.5. Some properties are listed in the following Table. Distinguish between metals and non-metals on the basis of these properties.
Q.6. Give reasons for the following.
(a) Aluminium foils are used to wrap food items.
Ans. Aluminium is malleable metal. It can be transformed into foil. The aluminium does not react with the food and retains it heat. Therefore, Aluminium foils are used to wrap food items.
(b) Immersion rods for heating liquids are made up of metallic substances.
Ans. Metals are good conductor of heat and electricity. Heat transfers quickly through metal and helps in heating liquid quickly. Therefore, Immersion rods for heating liquids are made up of metallic substances.
(c) Copper cannot displace zinc from its salt solution.
Ans. Zinc is more reactive than copper (or copper is comparatively less reactive than zinc). Therefore, Copper cannot displace zinc from its salt solution.
(d) Sodium and potassium are stored in kerosene.
Ans. Sodium and Potassium when exposed to air react vigorously with oxygen and water in it. They do not react with kerosene. To avoid reaction Sodium and potassium are stored in kerosene.
Q.7. Can you store the lemon pickle in an aluminium utensil? Explain.
Ans. No an aluminiium utensil cannot be used to store lemon pickle. Lemon are made of citric acid. Aluminium readily reacts with acids in lemon. The reaction can leach aluminium in pickle and spoil it.
Q.8. Match the substances given in column A with their uses given in column B.
Ans.
(i) Gold – (d) Jewellery
(ii) Iron – (e) Machinery
(iii) Aluminium – (c) Wrapping food
(iv) Carbon – (f) Fuel
(v) Copper – (b) Electric wire
(vi) Mercury – (a) Thermometers
Q.9. What happens when
Write word equations of the reactions involved.
(a) Dilute sulphuric acid is poured on a copper plate?
Ans. Nothing will happen as copper does not react with dilute sulphuric acid .
(b) Iron nails are placed in a copper sulphate solution?
Ans. Iron is more reactive that copper. When Iron nails placed in a copper suphate solution a displacement reaction will takes place and ferrous sulphate will be formed.
Copper sulphate (CuSO4) + Iron → Iron sulphate (FeSO4) + Copper
Q.10. Saloni took a piece of burning charcoal and collected the gas evolved in a test tube
(a) How will she find the nature of the gas?
Ans. She can find the nature of the gas by using a wet litmus paper. After bringing the litmus paper in contact with the gas, if it turns the blue litmus paper into red, it is acidic. Similarly, if it turn the red litmus into blue, it is basic.
(b) Write down the word equations of all the reactions taking place in this process.
Ans. (i) Carbon + Oxygen → Carbon dioxide
(ii) Carbon dioxide + Lime water → Milky
Q.11. One day Reeta went to a jeweller’s shop with her mother. Her mother gave an old gold jewellery to the goldsmith to polish. Next day when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?
Ans.
The gold jewellery is dipped into an acidic solution called aqua regia (a mixture of hydrochloric acid and nitric acid) for polishing. On dipping the gold jewellery in the acid solution, the outer layer of gold dissolves and the inner shiny layer appears. This causes a slight loss in its weight.
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