RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

Rajasthan Board RBSE Class 8 Science Chapter 2 Metals and Non-Metals

RBSE Solutions for Class 8 Science

RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

RBSE Class 8 Science Metals and Non-Metals Intext Questions and Answers

Page No 15.

Question 1.
Try identifying substances on the basis of their lustre (shine) and tabulated data In table.
Answer:
Table – Identificatlon of substances on the basis of their Lustre
RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-1

RBSE Class 8 Science Metals and Non-Metals Text Book Questions and Answers

Choose the correct option for the following:

Question 1.
The metal which is found in liquid state at room temperatures …………
(a) Sodium
(b) Magnesium
(C) Mercury
(d) Aluminium
Answer:
(C) Mercury

Question 2.
The non metal which is conductor of electricity.
(a) Coal
(b) Graphite
(C) Sulphur
(d) Nitrogen
Answer:
(b) Graphite

Question 3.
Which is most reactive from the following metals …………
(a) Gold
(b) Sodium
(c) Magnesium
(d) Silver
Answer:
(b) Sodium

Question 4.
Metal from ………. on reacting with oxygen.
(a) Acidic Oxides
(b) Basic Oxides
(c) Neutral Oxides
(d) None
Answer:
(b) Basic Oxides

RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

Fill in the blanks:

  1. Pure gold is _________ carat.
  2. The reaction of metals with acid gives out _________ gas.
  3. Metals are _________ of heat and electricity.
  4. The oxides of non metals are generally _________ in properties.

Answer:

  1. 24
  2. Hydrogen (H2)
  3. conductors
  4. acidic

Match the column A and column B:
RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-2

Answer:

  1. (b)
  2. (a)
  3. (d)
  4. (c)

Short Answer Questions:

Question 1.
What is malleability?
Answer:
The property of metal due to which it can be drawn into thin sheets when beaten is called malleability. Due to this property hammering.

Question 2.
What are mixed metals ?
(OR)
What is meant by mixed metals? Give two examples also.
Answer:
The homogenous mixture of metals and non metals or two metals in a definite proportions is called alloy or mixed metals. e.g. brass, bronze, stainless steel, etc.

Question 3.
What is melting point of substance?
Answer:
The definite temperature at which any solid changes into liquid state at normal atmospheric pressure is called melting point of the substance. Generally metals have high melting point and non metals have low melting point.

RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

Question 4.
Why is graphite conductor of electricity?
Answer:
Due to the presence of free electrons in the structure of graphite, it is a good conductor of electricity being a non metal.

Question 5.
Why lemon juice is not kept in Iron containers ?
Answer:
iron is a metal which reacts with acids. Lemon juice is acidic in nature due to which it reacts with iron to form poisonous substance. It makes the food item poisonous which is very bad for health. Therefore it is not stored in iron container.

Long Answer Questions:

Question 1.
Why Sodium metal is kept in kerosene?
(OR)
Sodium metal is kept in kerosene oil. What reaction takes place when it comes in contact with oxygen and water? Also write its chemical equation.
Answer:
Sodium metal is very active in nature. It reacts very fast with oxygen and water and forms sodium oxide and hydrogen gas and catches fire. To break the contact of sodium with air, it is kept in kerosene oil.
Equation of reaction:
RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-3

Question 2.
Differentiate metals and non – metals on the basis of their physical properties.
Answer:
RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-4

Question 3.
Write any four uses of metals?
Answer:

  1. Metals are used for making utensils.
  2. Copper wires are used in electronic appliances, radio, electric wires and cables, refrigerators, etc.
  3. Aluminium and iron sheets are used for protecting from rain and sun in the houses.
  4. Gold, silver and tin is used for making jewelry and coins.

RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

Question 4.
Why copper wire is use for wiring at our houses ? Explain.
Answer:
Metals are good conductor of heat and electricity. Silver is the best conductor of electricity. Copper, aluminium, iron, etc. are also good conductor of electricity. Silver is an expensive metal, hence, it is not generally used. But copper is a good conductor and there is also less wastage of energy. Therefore, copper is used in electric wiring at our houses.

Question 5.
Write differences in metals and non – metals on the basis of their chemical properties.
Answer:
RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-5

RBSE Class 8 Science Metals and Non-Metals Important Questions and Answers

Objective Questions:

Question 1.
From the following which can be beaten into sheet …………
(a) Zinc
(b) Phosphorus
(c) Sulphur
(d) Oxygen
Answer:
(a) Zinc

Question 2.
The reactive non metal that catches fire when kept open in air ………….
(a) Sodium
(b) Potassium
(c) Phosphorus
(d) Zinc
Answer:
(c) Phosphorus

RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

Question 3.
Which statement is correct in the following …………..
(a) All metals are ductile
(b) All non metals are ductile
(c) Generally metals are ductile
(d) Some non metals are ductile
Answer:
(c) Generally metals are ductile

Question 4.
Which of the following metal can be easily cut through knife ………….
(a) Sodium
(b) Mercury
(c) Copper
(d) Iron
Answer:
(a) Sodium

Question 5.
The best conductor of electricity among the following is ……………..
(a) Silver
(b) Lead
(c) Copper
(d) Aluminium
Answer:
(a) Silver

RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

Question 6.
Sodium metal is highly reactive. To prevent its contact from air, in which solution it is stored?
(a) in Water
(b) in Kerosene
(c) in Petrol
(d) In Glycerin
Answer:
(b) in Kerosene

Question 7.
The Non – metals form by the reaction of oxygen ……………
(a) Acidic oxide
(b) Basic oxide
(C) Neutral oxide
(d) None of these
Answer:
(a) Acidic oxide

Fill in the Blanks:

  1. Maximum …………. does not reacts with dilute acids.
  2. Maximum metals have …………. melting points.
  3. The oxide of magnesium is …………. in nature.
  4. Sodium metal is kept in ………….
  5. Metals react with acid to produce …………. gas.

Answer:

  1. non-metals
  2. high
  3. basic
  4. kerosene
  5. hydrogen

State whether the following statements are True or False –

  1. Coal can be drawn into wires.
  2. Non metals have less density.
  3. Sulfur is good conductor of electricity and graphite Is a bad conductor of electricity.
  4. Phosphorus reacts vigorously with water.

Answer:

  1. False
  2. True
  3. False
  4. False

Math the Column –

Question 1.
Match the following:

RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-6

Answer:

  1. (iv)
  2. (i)
  3. (ii)
  4. (iii)

Question 2.
Match the following:
RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-7

Answer:

  1. (b)
  2. (d)
  3. (C)
  4. (a)

Very Short Answer Questions:

Question 1.
What is the color of metals in general?
Answer:
The color of metals in general is grey.

RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

Question 2.
Metals are ductile. What is meant by this?
Answer:
Ductility in metals means they can he drawn into wires on stretching.

Question 3.
Give names of two metals that floats over water.
Answer:

  1. Sodium (Na)
  2. Potassium (K).

Question 4.
Name the metal which melts when kept on palm although metals have high melting point.
Answer:
The melting point of gallium (Ga) metal is very low, which melts when kept on palm.

Question 5.
Name one metal and one non metal which is liquid at room temperature.
Answer:
Metal → Mercury (Hg), Non – metal → Bromine (Br).

RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

Question 6.
Generally non metals arc not lustrous. Name two non metals which are lustrous.
Answer:

  1. Diamond
  2. Iodine.

Question 7.
What is the property of brittleness?
Answer:
Non metals on beating can be broken into small pieces. This is called brittleness.

Question 8.
Name two alloys used in our daily life?
Answer:

  1. Stainless Steel
  2. Brass

Question 9.
An element x on heating produces a white coloured powder. Give the chemical equation of this reaction.
Answer:
This element (x) is magnesium (Mg)
2Mg + O2 → 2MgO

Question 10.
What happen on rubbing a metal with sand paper?
Answer:
On rubbing with sand paper, the metals attains shine.

RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

Question 11.
Can you cut a piece of metal easily with knife Name such two metals which can be cut with knife like wax.
Answer:
No, maximum metals are hard solids that cannot be cut through knife. Metals that can he cut with knife like wax are

  1. Sodium (Na)
  2. Potassium (K).

Question 12.
Give the melting point of iron (Fe).
Answer:
The melting point of iron is 1593°C.

Question 13.
Can you tell why the utensils of copper and aluminium looks blackish at home?
Answer:
Copper and aluminium reacts with the oxygen of air and form copper oxide and aluminium oxide respectively. That is why the utensils of copper and aluminium looks blackish at home.

Short Answer Type Questions:

Question 1.
Observe the given table and complete it.
RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-8
(OR)
Write any two differences between metal and non-metal.
Answer:
RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-9

Question 2.
Generally metals sink in water. Why?
Answer:
Generally metals are heavy and are more heavier than water. Thus those substances that are heavy than water they will sink. e.g. iron, copper, etc. Some metals which are less denser than water floats over it e.g. sodium and potassium.

Question 3.
What is sonority?
Answer:
When the objects of metals are stricken with some hard material, they will produce a sound, for example – when the bell of the temple rang the sound is produced. Thus metal produced sound. On this basis only metals are called sonorous and this property is called sonority.

RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

Question 4.
What is meant by metal. Give examples.
Answer:
Metals – The materials that are hard, lustrous, with high density, good conductor of heat, malleable and are ductile, are known as metals, e.g. iron, copper, aluminium, etc.

Question 5.
What are non metals? Give examples.
Answer:
The materials that are soft, non lustrous, having low density, bad conductor of heat and electricity, non malleable and non ductile and are brittle are called non-metals, e.g. coal powder, sulphur. phosphorus. oxygen.

Question 6.
In which form do metals and non – metals found on the earth’s crust?
Answer:
On the crust of earth some metals like gold and platinum and some non – metals like sulphur and hydrogen etc. are found in free or natural state. Elements are found in free state while most of metals and non metals are found in combined state in the form of oxides, carbonates, suiphide and suiphates etc. on earths crust, for example some metals and non metals like aluminium, iron, manganese, oxygen. phosphorus are found in combined state.

Question 7.
The jewellery used by women and the utensils used in the household does not get rusted. Why?
Answer:
Jewellery used by women and the utensils used in the household does not get rusted because while making them jewellery and utensils some other metals or non metals are mixed with the main metal in a fixed ratio. Two or more than two metals or a metal and a non – metal can be mixed in a fixed ratio to obtain a desirable property. Thus they are made rust free.

Question 8.
How do non metals react with water? Why is phosphorus kept In water?
Answer:
Generally, non metals do not react with water. That is why, some non metals which are active in air are kept in water. Example: Phosphorus is a very active non metal, hence it is kept in water.

RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

Question 9.
What is meant by noble metals? Explain what is carat?
Answer:
Those metals which are not affected by water, oxygen, acid and base are called noble metals. Example : Gold, Silver, etc. The purity of gold is measured in carat. 24 carat gold is the purest gold. Pure gold is soft. Thus while making jewellery it is mixed with some amount of other metal and converts into, 22 carat or 20 carat gold. By this the hardness of gold increases.

Question 10.
Write the uses of non – metals.
Answer:
Uses of Non – metals –

  1. Sulphur is used for making acid, medicines and explosives
  2. Red phosphorous is used for making match sticks, crackers and pesticides.
  3. Graphite is used for making electrode.
  4. Graphite is also used in pencils.

Question 11.
Write some uses of metals.
Answer:
Uses of Metals –

  1. Mercury is used in thermometers.
  2. Sodium metal produces sodium chloride (table salt), sodium carbonate (washing soda) and sodium bicarbonate (eating soda) etc. which are used in daily use.
  3. Metals are used for making utensils.
  4. Electronic devices use copper wires.

RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

Question 12.
Sonu asked his mother not keep the lemon syrup in a brass-pot. Explain which pot should be used in place of brass pot? And why?
Answer:
The nature of lemon syrup is acidic. Acidic substances are not kept in iron or brass utensils because acid reacts with iron or brass and forms poisonous substance. It makes the food item poisonous which is harmful for health.

Essay Type Questions

Question 1.
Explain with an activity that the oxides of non-metals are acidic In nature?
Answer:
Generally oxides of non-metals are acidic in nature. It can be explained on the basis of following activity – Take a small amount of powdered sulphur in a dillagrating spoon and heat it. If you do not have diflagrating spoon then you can use any metallic cap of bottle. Now cover metallic cap of bottle with metallic wire.

As SOOfl as sulphur starts burning introduce the spoon into a gas zar or glass tumbler. Cover the tumbler with a lid to ensure that the gas produced does not escap. Remove the spoon after some time. Now add a small quantity of water into the tumbler and quickly replace the lid, shake the tumbler well.

Check the solution with red and blue litmus papers. You will observe that the blue litmus turns red. It confirms that the nature of solution is acidic. So we can say that oxides of hon metals is acidic in nature. The powdered sulphur reacts with air and produce sulphur dioxide gas, which is a non metallic acidic oxide.
Sulphur (S) + Oxygen (O2) → Sulphur dioxide (SO2)

Question 2.
Metals reacts with oxygen of air to form which type of oxides? Explain with the help of an activity diagramatically.
Answer:
All the metals reacts with oxygen of air and form basic oxides, which can be explained with the help of following activity. Take a thin ribbon of magnesium and burn it with the help of candle. We will observe that magnesium ribbon burns with dizzling white light and form a white coloured ash. Now take this ash in test tube and add some water and shake well this solution. Now perform litmus test of this solution. We will see that red litmus turns blue. It proves that the solution of metallic oxide is alkaline in nature.
RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-10

Question 3.
Compare the electrical conductivity of silver, copper, zinc and aluminium with the help of an activity and write them in this decreasing conductivity order.
Answer:
Activity –
1. Arrange the electric circuit according to the given figure.

2. The metal to be tested is attached between the terminal A and B of the circuit.

3. If the bulb glows then the metal is good conduct or and if the bulb does not glow then the metal is insulator of electricity. Generally we see that metals are good conductor whereas non metals are bad conductor of electricity. Metals in decreasing order of their conductivity

  1. Silver
  2. Copper
  3. Aluminium
  4. Zinc.

RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-11

Question 4.
Does metals a good conductor of heat? Explain it with the help of an activity diagrammatically.
Answer:
Generally metals are good conductors of heat. It can be explained with the help of following activity – lake a beaker made up of glass. Filled this bankcard with water approximate half of it. Put a steel spoon and a Woodcraft log into it. Now heat the beaker. After some time touch steel spoon and wooden log.
RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-12
We will observe that steel spoon becomes hot while wooden log not. Hence we can say thai metal (steel spoon) is good conductor of heat. Due to this reason all the utensils which arc used in making food, are made up of iron, copper and aluminium, etc. Silver (Ag) is the best conductor of heat while lead (Pb) is the least one.

Question 5.
The table given below has list of some properties. On the basis of these properties, differentiate between metals and non metals.
RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-13
Answer:
RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-14

Question 6.
Explain the main physical properties of metals.
Answer:
Metals can have following physical properties –
1. Physical State – At room temperature maximum metals are solid in state. Mercury (Hg) is the only metal which is liquid at room temperature.

2. Colour – Generally metals are of grey colour

3. Lustre – Metals have a fine lustre, it is known as metallic lusture. Silver, gold, aluminium, copper etc. are specific very shiny metals.

4. Hardness – Because generally metals are hard they cannot be cut easily. All the metals have different hardness. Some metals like sodium, potassium can he cut easily by knife like a wax. Which shows that sodium and potassium metals are soft in nature.

5. Sonority -When metals struck with any other solid materials then a specific metallic sound is produced. It is known as sonority. This property of metal is used in making bells and other musical instruments.

6. Denslty – Generally metals have high density.

7. Melting Point – The temperature at which any solid substance is converted into liquid state, is known as melting point of that substance. Metals have high melting points due to their hardness. e.g. the melting point of iron is 1593°C while Gallium (Ga) metal is an exception. It melts when put on palm because it has very low melting point. Generally it is liquid at room temperature.

8. Thermal Conductivity – Metals are good conductors of heat. Because of this the cooking utensils at home are made up of iron, copper and aluminium. Silver (Ag) is the best conductor and lead (Pb) is the least conductor of heat.

9. Malleability – The property of metals by which they can be beaten into thin sheets is called malleability. Due to this property we can made a thin sheet of metals.

10. Electrical Conductivity – Metals can conduct electricity hence they are good conductor of electricity. Silver (Ag) is the best conductor of electricity.

11. Ductility – The property of metals by which they are stretched into a wire, is known as ductility.

RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

Question 7.
Explain the physical properties of non -metals.
Answer:
Physical propertics of non-metals are as under –
1. Physical State – At room temperature non- metals can be found in solid, liquid and gaseous state : like Solid – Carbon (C), Sulphur (S), Iodine (I) Liquid – Bromine (Br) Gas – Oxygen (O2), Nitrogen (N2), Hydrogen (H2).

2. Colour – Non – metals are of vanous colour – Sulphur (yellow), chlorine gas (greenish yellow), Phosphorous (red + white), etc.

3. Lustre – Non – metals are non lustrous. They do not reflect light. Diamond and Iodine are its exception. They are shiny.

4. Hardness – Non – metals are not hard. They arc soft. Sodium can be cut through knife, Diamond cannot be cut through knife. It is an allotrope of carbon.

5. Sonority – Non – metals are non-sonorous. They do not produce sound when struck with hard substances.

6. Density – Non – metals have very low density.

7. Melting Point – Non-metals have very low density. But graphite and diamond are the allotropes of carbon exception. They have very high melting points.

8. Thennal and Electrical Conductivity – Generally non-metals are insulators they cannot conduct electricity but graphite is an exception which can conduct electricity so graphite is good conductor.

9. Brittleness – Non – metals are brittle in nature. When non-metals are beaten with the help of hammer, they are converted into powder. This property is known as brittleness.

RBSE Solutions for Class 8 Science Chapter 2 Metals and Non-Metals

Question 8.
Explain the reaction of sodium (Na) metal with water diagrammatically.
(OR)
What is formed when metal react with water? Write the reaction of sodium with water.
Answer:
Maximum metals reacts with water and form metallic oxide and hydrogen gas. Reaction of sodium with metal – Take a very small sodium piece and dry this piece on tiller paper. Now drop this piece into a beaker filled with water. We observe that it melts to from a silvery white globule which sand about the surface of the water with a hissing sound.

We will also observe a yellow flame over the globule and hear intermittent ‘pops’. It is because the heat evolved during the reaction melts the metal and the hydrogen gas produced catches fire. So we can say that sodium reacts with water and produce sodium hydroxide and hydrogen gas.

RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-15

RBSE Solutions for Class 8 Science Chapter 1 Metals and Non-Metals img-18

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