“Materials Metals and Non-Metals” is Chapter 11 taken from the JKBOSE textbook of Science for students of Class 8th. In the previous post, I provided you with Questions and Answers for Chapter 10 Reaching the Age of Adolescence. This post is about the Materials Metals and Non Metals Class 8 Question Answers. Before we move on to solutions you must have your basics clear. So, let me begin by giving you a brief overview of what you have studied in this chapter.
Materials Metals and Non Metals Class 8 Question Answers
Overview of Chapter
- PHYSICAL PROPERTIES OF METALS AND NON-METALS.
- CHEMICAL PROPERTIES OF METALS AND NON-METALS.
- Reaction with Oxygen.
- Reaction with Water.
- Reactions with Acids.
- Reactions with Bases.
- Displacement Reactions.
- USE OF METALS AND NON-METALS.
PHYSICAL PROPERTIES OF METALS AND NON-METALS: The properties of metals and non-metals which are due to their physical state are termed as physical properties of metals and non-metals.
- Malleability: The property which allows the metals to be hammered into thin sheets is called malleability. Metals are malleable whereas non-metals are brittle.
- Ductility: The property which allows the metals to be drawn into wires is called ductility. Metals are ductile whereas non-metals are not ductile.
- Conductivity: Metals are good conductors of heat and electricity whereas non-metals are poor conductors of heat and electricity.
- Sonorousness: Sonorous means capable of producing a ringing sound. Metals are sonorous whereas non-metals are not sonorous.
- Lustre: Metals are lustrous (shiny) in nature while non-meals are not lustrous. They are dull in appearance.
- Hardness: Metals are generally hard while non-metals are generally soft.
- Strength: Metals are generally strong (i.e. they can hold large weights) whereas non-metals are not strong.
CHEMICAL PROPERTIES OF METALS AND NON-METALS: The properties of metals and non-metals describe the ability of substances to react and form new substances.
- Reaction with Oxygen: Metals react with oxygen to form metal oxides. These are basic. Non-metals react with oxygen to form non-metal oxides. These are acidic.
- Reaction with Water: Metals react with oxygen to form metal hydroxide and hydrogen gas. Non-metals generally do not react with water.
- Reaction with Acids: Metals react with acids to form salts and hydrogen gas. Non-metals generally do not react with acids.
- Reactions with Bases: Some metals react with bases to form salts and hydrogen gas. Some non-metals react with bases but no hydrogen gas is produced. The reaction of non-metals with bases is complex.
- Displacement Reactions: A more reactive metal displaces a less reactive metal from its salt solution.
USE OF METALS.
- Iron, copper and aluminium are used for making cooking utensils.
- Copper metal is used for making electric wires for household wiring, electric motors, dynamos and many other electrical appliances.
- Aluminium metal in form of alloys is used for making aeroplanes.
- Aluminium foils are used for packaging medicines, chocolates, food items and many other materials.
- Iron metal is used to make nails, pipes, industrial tools and machines, buildings and bridges, railway lines, cars, buses and trains etc.
- Silver metal is used in jewellery.
- Mercury is used in thermometers.
- Zinc metal is used for galvanising iron objects.
USES OF NON-METALS
- Oxygen is a non-metal which is used by plants and animals for breathing.
- Nitrogen is a non-metal which is used for making fertilisers to enhance the growth of plants.
- Chlorine is used in process of purification of water.
- Iodine solution (tincture) is applied on wounds as an antiseptic.
- Carbon is used as fuel.
- Sulphur and phosphorus are used in fireworks such as crackers, etc.
Materials Metals and Non Metals Class 8th Questions
- Which of the following can be beaten into thin sheets?
Ans. a) Zinc
- 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.
- Fill in the blanks:
(a) Phosphorus is a very reactive non-metal.
(b) Metals are good conductors of heat and electricity.
(c) Iron is less reactive than copper.
(d) Metals react with acids to produce hydrogen gas.
- Mark ‘T’ if the statement is true and ‘F’ if it is false.
(a) Generally, non-metals react with acids. (False)
(b) Sodium is a very reactive metal. (True)
(c) Copper displaces zinc from zinc sulphate solution. (False)
(d) Coal can be drawn into wires. (False).
- Some properties are listed in the following Table. Distinguish between metals and non-metals based on these properties.
|1. Appearance||Shiny or Lustrous||Dull or non-lustrous|
|2. Hardness||Generally hard except for sodium and potassium||Generally soft, except for diamond|
|5. Heat Conduction||Good conductor of heat||Poor conductor of heat|
|6. Conduction of Electricity||Good conductor of electricity||Poor conductor of electricity|
- Give reasons for the following:
(a) Aluminium foils are used to wrap food items.
Ans. Aluminium is malleable and can be drawn into thin sheets. It does not react with food items and also protects them from spoilage.
(b) Immersion rods for heating liquids are made up of metallic substances.
Ans. Metals are good conductors of heat and electricity and they get hot very soon on passage of electric current. So, immersion rods are made of metals.
(c) Copper cannot displace zinc from its salt solution.
Ans. Copper is less reactive than zinc and less reactive metal cannot displace a more reactive metal from its salt solution.
(d) Sodium and potassium are stored in kerosene.
Ans. Sodium and potassium are highly reactive. They react vigorously with air and water and so are stored in kerosene.
7. Can you store lemon pickles in an aluminium utensil? Explain.
Ans. No, lemon pickles cannot be stored in an aluminium utensil because lemon contains acid and metal reacts with an acid to form metal salt and hydrogen gas. The metal salt is toxic which spoils our food and makes it unfit for use.
- 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|
|(i) Gold||(a) Thermometers|
|(ii) Iron||(b) Electric wire|
|(iii) Aluminium||(c) Wrapping food|
|(iv) Carbon||(d) Jewellery|
|(v) Copper||(e) Machinery|
|(vi) Mercury||(f) Fuel|
|Column I||Column II|
|(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|
- What happens when
(a) Dilute sulphuric acid is poured on a copper plate?
(b) Iron nails are placed in copper sulphate solution?
Write word equations of the reactions involved.
Ans. a) Copper does not react with dilute sulphuric acid so no reaction takes place.
- b) When an iron nail is placed in copper sulphate solution a displacement reaction takes place. Iron is more reactive than copper and will displace copper from its salt solution.
- 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. Carbon dioxide gas is produced by the burning of charcoal. The nature of gas can be checked by testing the aqueous solution of gas by using litmus paper. The solution will turn blue litmus red which shows that the gas produced is acidic.
(b) Write down word equations of all the reactions taking place in this process.
- One day Reeta went to a jeweller’s shop with her mother. Her mother gave old gold jewellery to the goldsmith to polish. The 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 outer layer of gold jewellery gets washed because gold is washed or polished in an acidic solution. During the process of polishing some gold gets dissolved in acid and this causes a loss of gold from jewellery.
- Why phosphorus is stored in the water?
Ans. Phosphorus is a very reactive non-metal. It reacts with air and catches fire but it does not react with water. So, it is stored in water.
That’s all about Materials Metals and Non Metals Class 8 Question Answers. Hope it has helped you. Do share your views about this post in the comment section below.