Class 8 Science Chapter 4 | Metals And Non-Metals | Important Questions
Here are important questions from Class 4 Science Chapter 4 Metals and Non-Metals. You can find multiple choice questions from this chapter here.
1. What are materials? Give example
Materials are substances with which we make various objects. Examples are: plastic, iron, wood etc.
2. Sulphur is a material. True/False
True
3. Metals can be distinguished from non metals on the basis of their …………………..and ………………………properties.
Chemical and physical
4. Lustre and hardness are chemical properties of metals. True/False
False (lustre and hardness are physical properties of metals)
5. Define the physical properties of metals? Give examples.
The physical properties of metals are as follows:-
Malleability – The property of metals by which they can be beaten into thin sheets is called malleability. Example: aluminium foil and silver sheets used to decorate sweets
Ductility – The property of metals by which they can be beaten into wires is called ductility. Example: copper wires
Sonorous- Metals produce a ringing sound. The sound produced by a metal coin or an iron sheet when they are dropped is quite different from the sound produced when a piece of wood is dropped. The materials which produce a ringing sound when struck hard are called sonorous. Metals are sonorous while non-metals are not sonorous.
Hardness – Metals are generally hard and cannot be broken with our hands or cut with a knife. Some exceptions are there but generally speaking metals are hard substances. Copper and iron, for example, are very hard. That is why they are used for making glasses and plates as they do not break when they are dropped
Lustre – Metals have a shiny appearance. For example, gold and silver are used for making ornaments because of their lustrous property.
Conductivity – Metals are good conductors of heat and electricity. That is why they are used for making electric wires and pans used for heating.
6. Metals are malleable and non-metals are not malleable. Explain with an activity.
The property of metals by which they change their shape to form thin sheets is called malleability.
Take a small iron nail, a coal piece, a piece of thick aluminium wire and a pencil lid. Beat the materials using a hammer. We can see that the iron nail and aluminium wires changed their shape but the piece of coal and pencil lid broke when beaten. This activity shows that metals are malleable and non-metals are not malleable.
7. Metals are sonorous and non-metals are not sonorous. Explain with an activity.
Metals produce a ringing sound when they are struck. It is this property that makes metals sonorous.
Take two boxes similar in appearance, one made of wood and the other of metal and strike both with a spoon or some other object. When we strike the metal box a ringing sound is produced and when we strike the wooden box no ringing sound is formed. Hence, it is clear that metals produce a ringing sound when they are struck.
8. List 6 physical properties of metals?
Metals are hard, malleable, lustrous, good conductors of heat and electricity (conductivity), ductile and sonorous
9. What are metals?
The materials which are hard, malleable, lustrous, good conductors of heat and electricity (conductivity), ductile and sonorous are generally known as metals. Metals possess many chemical properties too. Of course, there are a few exceptions. For example, sodium and potassium are soft metals and can be cut using a knife. Mercury exists in liquid state at room temperature.
10. What are non-metals?
Generally speaking, the materials which are soft and dull in appearance are non-metals. They break down into powdery mass when struck with a hammer. They are not sonorous and are poor conductors of heat and electricity.
11. Sodium and potassium are non-metals. True/false
False (sodium and potassium are metals.)
12. What is chemical property?
Chemical property of a substance shows how it reacts with another substance.
13. Complete the equation and rewrite it in the chemical name
a) Iron + oxygen + water = ……………………….
b) Magnesium + oxygen = ……………………
Answer = Iron + oxygen + water = iron oxide
In chemical form,
Fe+o2+h2o=Fe2O3
b) Magnesium + oxygen = magnesium oxide
in chemical form,
Mg + o2 = MgO
14. What is the nature of iron oxide? Explain with an activity. (with rust or magnesium)
Take a spoonful of rust and dissolve it in a very small amount of water. Shake it very well. Now test that solution with red and blue litmus paper. We see that the red litmus paper turns blue and the blue litmus paper remains blue itself. So, we conclude that oxides of metals are basic in nature.
15. The green material found on copper when exposed to air for long is a mixture of……………………and…………………..
Copper hydroxide and copper carbonate
16. write the chemical name for copper hydroxide and copper carbonate
Copper hydroxide – Cu(OH2)
Copper carbonate – CuCO3
17. How is greenish deposit on copper formed? Write the chemical reaction?
The greenish deposit on copper is formed when copper is exposed to air for long. The green deposit is a mixture of copper carbonate (CuCO3) and copper hydroxide {Cu(OH2)}.
Chemical reaction,
2Cu+H2O+CO2+O2 = Cu(OH)2 +CuCO3
18. What is the nature of magnesium ash when dissolved in water? Explain with an activity
Take a small piece of magnesium ribbon and burn it. After burning collect the ash and add it to water. Shake the solution well. Now test the solution with both red and blue litmus paper. It is found that the blue litmus paper remains blue and the red litmus paper turns into blue. Magnesium is a metal and it is clear by this that oxides of metals are basic in nature.
19. With the help of an experiment show that oxides of nonmetals are acidic in nature. Write the chemical name for this.
Sulphur is a nonmetal so we are conducting the activity with sulphur.
Take a small amount of powdered sulphur in a deflagrating spoon. Heat it, when it starts to burn, put the spoon of sulphur in a glass tumbler and close it with a lid. Don’t let the smoke go outside. After some time remove the spoon from the jar and add some water to the jar. Shake it very well. Now check the solution with blue and red litmus paper. The blue litmus paper changes its colour into red and the red litmus paper remains red itself. So, it is evident that oxides of nonmetals are acidic in nature.
Chemical name,
S+O2 = SO2
SO2 + H2O = H2So3
20. What is the name of the new substance formed as a result of the reaction of sulphur and oxygen?
Sulphur dioxide gas
21. What is the new product formed when sulphur dioxide is mixed with water? Write the chemical name of the substance formed and the chemical reaction happened.
The new product formed when sulphur dioxide is mixed with water is sulphurous acid. The chemical name for sulphurous acid is (H2SO3)
The chemical reaction happened is,
Sulphur dioxide + water =sulphurous acid
(SO2) + (H2O) = (H2SO3)
22. Generally, oxides of nonmetals are acidic in nature. True/False
True
23. Sulphur metals is very reactive with oxygen and water. True/False
False (Sodium metal is very reactive with water and oxygen)
24. Why is sodium stored in kerosene?
Sodium metal is very reactive. It reacts vigorously with oxygen and water. A lot of heat is generated during the reaction. It is, therefore, stored in kerosene.
25. Sodium reacts vigorously with water. Explain with the help of an activity?
Take a 250 mL beaker/glass tumbler. Fill half of it with water. Cut a small piece of sodium metal. Dry it using filter paper and wrap it in a small piece of cotton. Put the sodium piece wrapped in cotton into the beaker. Observe carefully. When the reaction stops touch the beaker. We notice that the beaker is hot. This is because sodium catches fire when put into water. Test the solution with red and blue litmus papers. The red litmus paper turns blue this means that the solution is basic in nature.
26. Iron reacts slowly with water. True/false
True
27. Which metal reacts with cold water?
Magnesium
28. Name the metal which catches fire when put into water?
Sodium
29. Which nonmetal reacts with air and thus stored in water?
Phosphorus
30.Why phosphorus is stored in water?
Phosphorus is a very reactive non-metal. It catches fire if exposed to air. To prevent the contact of phosphorus with atmospheric oxygen, it is stored in water.
31. Generally nonmetals do not react with water. True/False
True
32. With the help of an activity check whether metals and nonmetals react with acids?
Take four test tubes and label them as a, b, c, d, e. In the test tube A put some zinc granules, in the test tube N put some iron in the test tube C put some charcoal in the test tube D put some sulphur and in the test tube E put some copper. Close the mouth of the test tube with a cork fixed with a funnel. Add 5ml of dilute hydrochloric acid to each of the test tubes. Observe the reaction. In the test tubes A and B gases are formed and in the test tubes C and D no gas is formed. As we know zinc and iron are metals and charcoal and sulphur are nonmetals. Now bring a burning match stick to near the mouth of each test tube. We can notice that the gases formed in test tube A and B start burning redly with a pop sound, but nothing happens to test tube C and D. We notice that there is no reaction taking place in the test tube E even though copper is a metal. Copper does not react with dilute hydrochloric acid even on heating but it reacts with sulphuric acid. Now we conclude that when acids react with metals a gas is produced and it is hydrogen gas. Generally, nonmetals do not react with acids.
33. Do metals react with bases? Explain with an activity.
Prepare a fresh solution of sodium hydroxide in a test tube by dissolving 3-4 pellets of it in 5 ml of water. Drop a piece of aluminium foil into it. Bring a burning match stick near the mouth of the test tube. Observe carefully. A pop sound is formed this means that metals react with sodium hydroxide to produce hydrogen gas.
34. Reactions of non-metals with bases are…………………….
complex
35. Is there a difference in the way metals and non metals react with acids?
Yes, when metals react with acid, they give hydrogen gas which makes a pop sound when a burning matchstick is brought near the mouth of the test tube, and when nonmetals react with acid no gas is formed.
36. What could the pop sound in some cases be due to when a burning match stick is brought near the mouth of the test tube?
Metals react with acid by releasing hydrogen gas which starts burning when a match stick is brought near the mouth of the test tube. Here, the pop sound indicates the hydrogen gas.
37. The chemical name for sodium hydroxide is ……………..
NaOH
38. What is displacement reaction?
Displacement reaction is the reaction in which the more reactive metal will replace the less reactive metal from their compounds in aqueous solutions.
39. How does the displacement reaction between zinc and copper occur?
Displacement reaction is reaction in which the more reactive metal will replace the less reactive metal. When zinc is added to copper sulphate, we get zinc sulphate and copper. Here zinc is more reactive than copper. Since zinc is more reactive than copper, zinc will replace copper from its compound. The chemical reaction for this is
Copper sulphate (blue) + zinc = zinc sulphate (colourless) + copper (red)
(CuSo4) + (Zn) = (ZnSo4) + (Cu)
40. With the help of an activity explain displacement reaction between iron nail and copper sulphate solution?
Take a beaker and pour 50 ml of copper sulphate solution. Now put some iron nails in the solution. Leave it undisturbed for a while. Now observe that the colour of copper sulphate solution change to green and the colour of the iron will change to brown. This is because the more reactive metal iron will replace the less reactive copper to form iron sulphate.
The chemical formula,
CuSo4 + Fe = FeSo4 + Cu
41. Why there is no reaction taking place when copper and iron is added to zinc sulphate?
Displacement reaction is reaction in which the more reactive metal will replace the less reactive metal from their compounds. Zinc is more reactive than copper and iron so copper/iron cannot replace zinc in its compound zinc sulphate.
42. Copper cannot replace zinc. What is the rule here by displacement reaction?
The rule here is that zinc is more reactive than copper. A more reactive metal can replace a less reactive metal, but a less reactive one cannot replace a more reactive metal.
43. Write the sequence of metals from reactive to less reactive among zinc, iron and copper?
Zinc is more reactive than copper and iron is more reactive than copper so the sequence is
Zinc (Zn) > Iron (Fe) > Copper (Cu)
44. Which non-metal is essential for our life which all living beings inhale during breathing
Oxygen(O2)
45. Non-metals used in fertilisers to enhance the growth of plants
Phosphorus (P), Nitrogen(N)
46. Non-metal used in water purification process
Chlorine (CI)
47. Non-metal used in the purple coloured solution which is applied on wounds as an antiseptic
Iodine (I2)
48. Non-metal used in crackers
Phosphorus (P)
