NCERT Exemplar for Class 8 Science Solutions Chapter 4 Materials: Metals and Non-Metals

Multiple Choice Questions

1. Which of the following is not a metal?

(a) Copper 

(c) Aluminium

(b) Sulphur 

(d) Iron
Ans: From the above options only sulphur is non-metal. So the correct option is (b).

2. The substance that will be flattened on beating with a hammer is

(a) Crystal of iodine 

(b) Lump of sulphur 

(c) Piece of coal

(d) Zinc granule

Ans: All the metals get flattened upon striking with a hammer. Non-metals break into small pieces. Thus, zinc granule will get flattened while hammered so the correct option is (d).

3. Boojho has learnt that non-metals on beating with a hammer are generally broken into pieces. Which of the following is a non-metal?

(a) Iron nail 

(b) Aluminium wire 

(c) Copper plate

(d) Piece of coal

Ans: The correct option is (d). When a piece of coal is stroked with a hammer, it breaks into pieces. So it’s a nonmetal.

4. Materials which can be drawn into wires are called ductiles. Which of the following is not a ductile material?

(a) Silver 

(b) Copper 

(c) Sulphur

(d) Aluminium

Ans: Sulphur is not ductile because it’s a non-metal therefore, the correct option is (c).

5. Metals are generally hard. Which of the following metals is an exception and can be cut with a knife?

(a) Iron 

(b) Sodium 

(c) Gold

(d) Magnesium

Ans: Sodium is soft metal so it can be cut with a knife; therefore, the correct option is (b).

6. Metals are generally solid. Which of the following metals is in the liquid state at room temperature?

(a) Mercury 

(b) Silver 

(c) Aluminium

(d) Sodium

Ans: Mercury is a liquid state metal. At room temperature mercury becomes liquid therefore, the correct option is (a).

7. Metals generally react with dilute acids to produce hydrogen gas. Which one of the following metals does not react with dilute hydrochloric acid?

(a) Magnesium 

(b) Aluminium 

(c) Iron

(d) Copper

Ans: Less reactive metals such as silver, copper, gold etc don’t react with dilute hydrochloric acid. So, these metals do not produce hydrogen gas therefore, the correct option is (d).

8. Which of the following reacts with cold water vigorously?

(a) Carbon 

(b) Sodium 

(c) Magnesium

(d) Sulphur

Ans: Reactivity of a chemical decides the intensity of reaction of a metal with water. Sodium being a very reactive metal reacts very violently; therefore, the correct option is (b).

9. The metal which produces hydrogen gas on reaction with dilute hydrochloric acid as well as sodium hydroxide solution is

(a) Copper 

(b) Iron 

(c) Aluminium

(d) Sodium

Ans: Sodium Hydroxide solution as well as Hydrochloric acid on reaction with Aluminium produces hydrogen gas therefore, the correct option is (c).

10. Which of the following non-metals reacts and catches fire on exposure to air?

(a) Phosphorus 

(b) Nitrogen 

(c) Sulphur

(d) Hydrogen

Ans: Phosphorus is a non-metal and when exposes to air, blasts, therefore, the correct option is (a).

11. Generally metallic oxides are basic and non-metallic oxides are acidic in nature. Solution of which of the following oxides in water will change the colour of blue litmus to red?

(a) Sulphur dioxide 

(b) Magnesium oxide 

(c) Iron oxide

(d) Copper oxide

Ans: Sulphur forms acidic oxide, i.e. Sulphur dioxide and turns blue litmus red therefore, the correct option is (a).

12. Which of the following property is not responsible for copper to be used as electrical conduction wires?

(a) Ductility 

(b) Colour 

(c) Good conductor of electricity

(d) It is solid

Ans: Copper’s colour doesn’t decide for its conductivity property, therefore, the correct option is (b).

VERY SHORT ANSWER QUESTIONS

13. Name two soft metals which can be cut with a knife.

Ans: Following metals are soft metals so can be cut easily with a knife-

(i) Potassium

(b) Sodium

14. Which non-metal is essential for our life and all living beings inhale it during breathing?

Ans: Oxygen is a non-metal is essential for our life and all living beings inhale it during breathing .

15. Name two major non-metals which are present in fertilisers and enhance the growth of plants.

Ans: The two major non-metals which are essential for fertilisers are:

(i) Phosphorus

(ii) Nitrogen

16. Which non-metal is used to disinfect water?

Ans: Chlorine is a non-metal and possesses a quality of killing water germs so it is used in water purifiers to disinfect water.

17. A purple coloured non-metal forms a brown solution in alcohol which is applied on wounds as an antiseptic. Name the non-metal.

Ans: Tincture of Iodine is a purple coloured solution formed with Iodine (a non-metal). It is used as an antiseptic to apply on wounds.

18. Zinc sulphate forms a colourless solution in water. Will you observe any colour on adding copper turning in it?

Ans: Copper is less reactive. So, when it is added to zinc sulphate solution it doesn’t displace zinc from the salt solution. Hence, displacement reaction doesn’t take place.

19. Why are bells made of metals?

Ans: Metals produce ringing sound which is known as a sonorous property. Thus used to make bells.

20. Which liquid metal is used for making thermometers?

Ans: Mercury is the metal which is used to make thermometers.

21. Which of the following metals can displace the other two metals from their salt solutions?
Zinc, iron, copper

Ans: Following is the reactivity order of the given metals-

Zinc > Iron > Copper

As zinc metal has the most reactive property, it can displace other two metals from, their salt easily.

SHORT ANSWER QUESTIONS

22. Paheli bought a statue made of copper. To her surprise it acquired a dull green coating after a couple of months. Explain the reason.

Ans: Copper upon reaction with moist air forms Copper Hydroxide and Copper Carbonate and acquires dull green color which is also known as corrosion of copper. The below reaction, will help us in understanding this process-

$2 \mathrm{Cu}+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2}+\mathrm{O}_{2} \rightarrow \mathrm{Cu}(\mathrm{OH})_{2}+\mathrm{CuCO}_{3}$

23. In Fig 4.1 you find that the bulb glows when an iron nail is placed between two ends of wire. Complete the following sentences on the bases of this fact. Fig 4.1

(a) Is a metal.

(b) Metals are good of electricity.

Ans: (a) Iron

(b) Conductors

24. If in Fig. 4.1 iron nail is replaced by a wooden stick, will the bulb glow or not? Justify your answer.

Ans: No, the bulb will not glow as the wooden stick is an insulator and doesn’t help electricity to flow in it.

25. Paheli prepared a blue coloured solution of copper sulphate in beaker A and placed an iron nail in it. Boojho prepared a yellowish green solution of ferrous sulphate in beaker B and placed a copper wire in it. What changes will they observe in the two beakers after an hour?

Ans: Iron is more reactive than Copper and thus it displaces Copper from its salt solution. In beaker A, copper’s reddish brown layer will deposit on the iron nail and copper sulphate’s blue colour solution will become yellowish green because this process forms Iron Sulphate. In beaker B, There’s no change because the less reactive property of copper doesn’t be able to displace iron from ferrous sulphate solution.

26. A doctor prescribed a tablet to a patient suffering from iron deficiency. The tablet does not look like iron. Explain.

Ans: The medicine give to the patient is in slat form, whether iron remains in metallic form, thus the tablet doesn’t look like iron.

27. Match the substances in Column A with their applications given in Column B.

Ans: The correct options are:
(a) (iii)
(b) (iv)
(c) (i)
(d) (v)
(e) (ii)

LONG ANSWER QUESTIONS

28. Some of the following statements are incorrect. Find the incorrect statements and correct them.

(a) The property of metals by virtue of which they can be drawn into wires is called ductility.

(b) Metals are good conductor of electricity but poor conductor of heat.

(c) Articles made of metals produce ringing sound when struck hard.

(d) Oxides of non-metals and metals are acidic in nature.

(e) A less reactive metal replaces a more reactive metal from its salt solution in water.

Ans: 

The statement (a) is true.

The statement (b) is false since, being a good conductor let the electricity and heat pass through it.

The given statement (c) is true. Metals are sonorous.

The given statement (d) is false as oxides are metals which are basic in nature and oxides or non-metals are acidic in nature.

The given statement (e) is false. More reactive metals displace less reactive metals from its salt solution.

29. Iron is more reactive than copper. Can you write an activity to show this?

Ans: Iron is more reactive than copper as it is required in copper sulphate solution, Iron nail, test tube.

Method- In the test tube, pour copper sulphate solution. Drop the iron nails in it and wait for the reaction to take place.

Observation- Solution turns blue. The nail which is in the contact with the solution turns reddish-brown.

Conclusion- The above process can be understood by the following equation-

$\mathrm{Fe}+\mathrm{CuSO}_{4} \rightarrow\mathrm{FeSO}_{4}+\mathrm{Cu}$

This kind of reaction is an example of displacement reaction. Here, iron displaces copper and adds up to the salt solution which is only possible if the replacing metal is more reactive than the shifting metal. Thus, it is verified that iron is more reactive than copper.

30. Fill in the blanks to complete the following paragraph. 

The name of the product formed in the reaction of sulphur and ______ is sulphur dioxide gas. When sulphur dioxide is dissolved in _______, sulphurous acid is formed. The sulphurous acid turns ______ litmus paper to ______. Generally oxides of ________ are acidic in nature.

After completing the paragraph write two questions which you can raise on the basis of this information.

Ans: The name of the product formed in the reaction of sulphur and oxygen is sulphur dioxide gas. When sulphur dioxide is dissolved in water, sulphurous acid is formed. The sulphurous acid turns blue litmus paper to red. Generally oxides of non-metals are acidic in nature.

The following questions can be asked-

(i) What is the nature if oxides?

(ii) Which gas is formed when sulphur reacts with oxygen?

31. Find out the names of three metals and three non-metals from the box given as Fig 4.2.

Ans: The names of three metals and three non-metals from the box given are:

Metals: Copper, Metal Iron

Non-metals: Sulphur, Oxygen, Carbon.

32. Complete the crossword given in Fig. 4.3 with the help of the clues.

Across

1. Which is generally hard, ductile, malleable, and sonorous?

2. A metal is called so it can be drawn into wires.

3. Metal bells are used because of this property.

Down

4. A metal generally used for making jewellery.

5. A metal which is liquid at room temperature.

6. A metal which reacts with acid as well as base to form hydrogen gas.

7. Substances used to enhance the growth of plants.

8. Property by virtue of which metals can be beaten into thin sheets.

Ans:

Across-

1- Metal 

2- Ductile 

3- Sonorus

Down-

4- Gold 

5- Mercury 

6- Aluminium

7- Fertiliser 

8- Malleable 

Uses of Metals

Along with its strength and endurance, metals are used to make equipment, machinery, airplanes, vehicles, and nails, among other things. Due to their shiny characteristics, metals such as gold and silver are used to make jewelry. Copper and aluminum are utilized to manufacture wires because of their ductile properties and ability to carry electricity. The metal mercury is used in thermometers. In the electroplating and steel industries, metals such as nickel and chromium are employed. Batteries are made from metals such as lead. Aluminum, for example, is utilized as a packing material because it can be folded into sheets.

Uses of Non-Metals

Among the essential non-metallic elements, oxygen is necessary for our survival, as is carbon for plants. Fertilizers commonly use non-metals such as nitrogen and phosphorus. Rockets are propelled by non-metal materials such as liquid hydrogen. In pencils, non-metal graphite is necessary.

Physical Properties of Metals

Metals can be pounded into thin sheets due to a feature they possess. The word for this attribute is malleability. This enables a material to change shape and form thin sheets, such as silver or aluminum foil. Metals also have a characteristic called ductility that allows them to be pulled into wires. It is because of this feature that metals such as copper may be pulled into wires. Metals are excellent heat conductors and are consequently used to make cooking utensils, irons, and heaters, among other things. Metals like copper and aluminum are used to make electric lines and cables because they are good conductors of energy. When hammered firmly, the metals have the unique feature of producing a ringing sound. This is referred to as resonant. When you strike a metal surface, you hear a sound because of this feature. Gold and silver, for example, have a gleaming or brilliant aspect.

Physical Properties of NonMetals

When non-metals are brittle and disintegrate into powder when hammered, they are non-malleable. Sulfur, for example, develops into a powdery substance. Except for carbon, non-metals are not ductile because they cannot be pulled into wires. Carbon fibers are commonly employed in sports and musical instruments. Except for graphite, which is the only non-metal that conducts heat and electricity, non-metals are poor conductors of heat and electricity. The non-metals are not sonorous, and when hit, they make no sound. When a wooden box is struck, it does not generate a ringing sound. Non-metals are non-lustrous, which means they have a soft, dull appearance, similar to charcoal.

Chemical Properties of Metal

Metal oxides are formed when metals react with oxygen to generate basic metal oxides. A red litmus paper dipped in a rust solution (which is essentially a metal, iron) becomes blue, suggesting the creation of a primary metal oxide. Some metals react quickly with water, such as sodium, which is why it is preserved in kerosene, whereas others, such as iron, react slowly. Metals react with water to generate metal hydroxides and hydrogen gas in general. Metal salts and hydrogen gas are formed when metals react with acids. When a burning matchstick is placed at the opening of a test tube containing magnesium ribbon and weak hydrochloric acid, a pop sound is produced owing to the combustion of hydrogen gas produced during the reaction.

Metal salts and hydrogen gas are formed when metals such as aluminum and zinc combine with bases such as sodium hydroxide to generate metal salts and hydrogen gas, which burns with a pop sound. Metals in aqueous solutions tend to displace more reactive metals from less reactive metals in their compounds. We can observe that the blue color of copper sulfate and aqueous zinc solution fades, and a red deposit forms at the bottom. This is because zinc is more reactive than copper, so it replaces it and creates zinc sulfate, releasing the red copper.

Chemical Properties of NonMetals

Non-metals usually react with oxygen to form non-metallic oxides, which are acidic. Sulfur interacts with oxygen to form sulfur dioxide gas, as can be seen. When this is dissolved in water, sulfurous acid is formed, which causes blue litmus paper to become red, showing that it is acidic. Non-metals do not usually react with water, although they can be pretty reactive in air. When exposed to oxygen in the air, phosphorus in water becomes highly reactive. In terms of appearance, non-metals react with any of the acids.