RBSE Class 10 Science Solutions Chapter 3 Metals and Non-metals

RBSE Class 10 Science Solutions Chapter 3 Metals and Non-metals

RBSE Class 10 Science Chapter 3 Metals and Non-metals InText Questions and Answers

Page 40.

Question 1.
Give an example of a metal which
(i) is a. liquid at room temperature
(ii) can be easily cut with a knife
(iii) is the best conductor of heat
(iv) is a poor conductor of heat
Answer:

• Mercury is a metal which is liquid at room temperature.
• Sodium metal can be easily cut with a knife.
• Copper is the best conductor of heat.
• Lead is poor conductor of heat.

Question 2.
Explain the meanings of malleable and ductile.
Answer:
Malleable metals can be beaten into a thin sheets. This property is called malleability and such metals are called malleable. Gold and silver are more malleable metals.
Ductile:
The ability of metals to be drawn into thin wires, is called ductility and these metals are called ductile. Gold is the most ductile metal.

Page 46.

Question 1.
Why is sodium kept immersed in kerosene oil?
Answer:
Sodium reacts vigorously with oxygen and catch fire if kept in open. Hence, to protect it and to prevent accidental fires, they are kept immersed in kerosene oil.

Question 2.
Write equations for the reactions of
(i) Iron with steam
(ii) Calcium and potassium with water.
Answer:

Question 3.
Samples of four metals A, B, C and D were taken and added to the following solutions one by one. The results obtained have been tabulated as follows:

Use the Table above to answer the following questions about metals A, B, C and D.
(i) Which is the most reactive metal?
(ii) What would you observe if B is added to a solution of copper (II) sulphate?
(iii) Arrange the metals A, B, C and D in the order of decreasing reactivity.
Answer:
(i) Metal B is the most reactive metal, because it gives displacement reaction with Iron (II) Sulphate.

(ii) When metal B is added to a solution of copper (II) sulphate, displacement reaction takes place and as a result of it the blue colour of the solution of copper II sulphate fades away and copper displaced and get deposited on metal B.

(iii) Metal B is most reactive as it displaces iron from its solution.

• Metal A is less reactive because it displaces copper from its solution.
• Metal C is even less reactive because it can only displace silver from its solution.
• Metal D is the least reactive because it cannot displace any metal from its solution.
• Hence the decreasing order of the reactivity of metals will be as follows as: B > A > C > I

Question 4.
Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H₂SO₂
Answer:
When dilute hydrochloric acid (HCl) is added to a reactive metal, then Hydrogen (H₂) gas is liberated. When iron reacts with dilute H₂SO₄ the chemical reaction occurs is:

Question 5.
What would you observe when zinc is added to a solution of iron (II) sulphate? Write the chemical reaction that takes place.
Answer:
Zinc is more reactive in comparasion to iron therefore, zinc will replace iron from the solution of iron (II) sulphate, as a result of which the light green colour of iron sulphate solution becomes colourless.
The chemical reaction takes place is:

Page 49.

Question 1.
(i) Write the electron-dot structures for sodium, oxygen and magnesium.
(ii) Show the formation of Na₂O and MgO by the transfer of electrons.
(iii) What are the ions present in these compounds?
Answer:
(i) The representation of elements with valence electrons as dots around the elements is referred to as electron dot structure for elements.
Sodium (2, 8, 1) = , Oxygen (2, 6) :0 , Magnesium, (2, 8, 2) = Mg

(iii) Ions present in Na₂O:
Cation = Na⁺¹ (Sodium cation)
Anion O^–2 (Oxide anion)

Ions Present in MgO:
Cation = Mg²⁺ (Magnesium cation)
Anion = O^2- (Oxide anion)

Question 2.
Why do ionic compounds have high melting points?
Answer:
Ionic compounds have strong inter ionic attraction force which is called electrostatic force of attraction. Therefore, it requires a lot of energy to break these forces. That is why ionic compounds have high melting points.

Page 53.

Question 1.
Define the following terms:
(i) Mineral
(ii) Ore
(iii) Gangue.
Answer:
(i) Mineral: The elements or compounds, which found naturally in the Earth’s crust are called minerals.

(ii) Ore: At some places, minerals contain a very high percentage of a particular metal and the metal can be profitably extracted from it. These minerals are called ores. Example, Cinnabar [HgS] is an ore of mercury.

(iii) Gangue: The impurities (sand, soil, gravel, etc.) present in the ore are called Gangue.

Question 2.
Name two metals which are found in nature in the free state.
Answer:
Gold and Platinum metals are found in nature in the free state.

Question 3.
Which chemical process is used for obtaining a metal from its oxide?
Answer:
The chemical process used for obtaining a metal from its oxide is reduction. For this carbon and active metals like Al are used as reducing agents.

Page 55.

Question 1.
Metallic oxides of zinc, magnesium and copper were heated with the following metals:

In which cases will you find displacement reactions taking place?
Answer:
A metal with higher reactivity will displace metal of lower reactivity from their compound. Among zinc, magnesium and copper, magnesium is most reactive whereas copper is least reactive. Therefore, in the following situation, displacement reaction will be as:

Question 2.
Which metals do not corrode easily?
Answer:
The unreactive metals which does not react with air, water and acids do not corrode easily. Example: Gold and Platinum.

Question 3.
What are alloys?
Answer:
A homogeneous mixture of two or more metals or a metal and a non-metal is called alloy. Alloy is prepared by first melting the primary metal and then, dissolving the other elements in indefinite proportions. It is then cooled to room temperature. Example: Steel is an alloy of iron and carbon.

RBSE Class 10 Science Chapter 3 Metals and Non-metals Textbook Questions and Answers

Question 1.
Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal
(b) MgCl₂ solution and aluminium metal
(c) FeSO₄ solution and copper metal
(d) AgNO₃solution and copper metal.
Answer:
(d) AgNO₃solution and copper metal.

Question 2.
Which of the following methods is suitable for preventing an iron frying pan from rusting?
(a) Applying grease
(b) Applying paint
(c) Applying a coating of zinc
(d) All of the above.
Answer:
(c) Applying a coating of zinc.

Question 3.
An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be:
(a) calcium
(b) carbon
(c) silicon
(d) iron
Answer:
(a) calcium.

Question 4.
Food cans are coated with tin and not with zinc because:
(a) zinc is costlier than tin
(b) zinc has a higher melting point than tin
(c) zinc is more reactive than tin
(d) zinc is less reactive than tin
Answer:
(c) Zinc is more reactive than tin.

Question 5.
You are given a hammer, a battery, a bulb, wires and a switch.
(a) How could you use them to distinguish between samples of metals and non-metals?
(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.
Answer:
(a) (i) If the given sample is broken into pieces on beating with hammer then it is non-metal but if it is converted into thin sheet then it is metal because metals are malleable.

(ii) A circuit is prepared by connecting given apparatus (battery, bulb, wire and switch) and the given sample is inserted between two terminals, if bulb will glow when switch is on then the sample is metal because metals are good conductor of electricity. If the bulb will not glow then sample is non-metal.

(b) (i) Metals are malleable therefore, they can be beaten up into thin sheets and can be used in making different types of utensils, containers and other items whereas this cannot be done in non-metals.

(ii) Metals are good conductors of electricity therefore, it is used in making electric circuit wires, whereas not from non-metals.

Question 6.
What are amphoteric oxides? Give two examples of amphoteric oxides?
Answer:
Oxides that behave as both acidic and basic oxides means they react with acid and base both and forms salt and water are called amphoteric oxides.
Example: Aluminium oxide (Al₂O₃), Zinc oxide (ZnO).
Aluminium oxide reacts with acid and base in the following manner:

Question 7.
Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
Answer:
Metals that are more reactive than hydrogen and displace it from dilute acids are Magnesium and Zinc.
Metals that are less reactive than hydrogen and do not displace it from dilute acids are copper and silver.

Question 8.
In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?
Answer:
In the electrolytic refining of a metal M; anode, cathode and electrolyte taken as:
Anode → Impure metal Cathode → Thin strip of pure metal Electrolyte → Solution of salt of the metal
Example: CuSO₄solution is used in the purfication of copper.

Question 9.
Fratyush took sulphur powder on a spatula and heated it. He collected the gas
evolved by inverting a test tube over it, as shown in figure below:

(a) What will be the action of gas on:
(i) dry litmus paper?
(ii) moist litmus paper?
(b) Write a balanced chemical equation for the reaction taking place.
Answer:
When sulphur powder is heated in air then sulphur dioxide gas is formed.
(a) (i) There will be no action of gas evolved (SO₂) on dry litmus paper.

(ii) Since the gas is sulphur dioxide (SO₂), it turns moist blue litmus paper to red because sulphur dioxide is acidic oxide means reacts with moisture to form sulphurous acid.

(b) Balanced chemical equation for the reaction taking place.

Question 10.
State two ways to prevent the rusting of iron.
Answer:
Two ways to prevent the rusting of iron are as follows:

• By applying oil, grease or paint on the surface of iron.
• Galvanisation: Surface of iron is coated with the layer of zinc metal.

Question 11.
What type of oxides are formed when non-metals combine with oxygen?
Answer:
Non – metals combine with oxygen and forms two types of oxides: Acidic and Neutral.
For Example:
N₂O₃ or N₂O₃ is an acidic oxide whereas CO is a neutral oxide.

Question 12.
Give reasons:
(a) Platinum, gold and silver are used to make jewellery.
(b) Sodium, potassium and lithium are stored under oil.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
Answer:
(a) Platinum, gold and silver are in the lower side of reactivity series means reactivity of these is very less. So they do not react easily with oxygen and moisture present in atmosphere and also with acids. These metals do not corrode easily so lusture is maintained. These metals are malleable and ductile. Due to these reasons platinum, gold and silver are used to make jewellery.

(b) Sodium, potassium, and lithium are very reactive metals and react vigorously with air as well as moisture present in atmosphere and forms oxide and hydroxide. So if these are kept open, they catch fire. Therefore, they are stored under kerosene oil in order to prevent their contact with air and moisture. Hence these are safe and accidental fire is controlled.

(c) Aluminium is a highly reactive metal so at ordinary temperature it reacts with oxygen present in air to form a thin layer of aluminium oxide. This layer prevent the aluminium from further oxidation, and corrosion. Aluminium is good conductor of heat so it is also used to make utensils for cooking.

(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction because metals can be easily extracted from their oxides rather than from their carbonate and sulphide.

Question 13.
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
Answer:
Copper reacts with moist carbon dioxide in air to form basic copper carbonate and due to whi.ch copper vessel becomes tarnished. The acid present in the lemon or tamarind reacts with basic copper carbonate and dissolves the layer. That is why, tarnished copper vessels are cleaned with lemon or tamarind juice.

Question 14.
Differentiate between metal and non-metal on the basis of their chemical properties.
Answer:
These are the differences between metal and non-metals on the basis of their chemical properties.
1. Metals are electropositive so they lose electrons easily and form cations while non-metals are electronegative so they gain electrons and form anions.

2. Metals forms basic oxides by oxidation in air white non-metals forms acidic and neutral oxides.

3. Metal oxides forms Alkali by the reaction with water and salt with acids while non-metal oxides forms acid by the reaction with water and salt with Alkali.

4. Metals forms oxide and H₂ by the reaction with water also while non-metals do not so.

5. Metals forms salt and H₂ by the reaction with dilute hydrogen acids while non-metals do not react with dilute hydrogen acids.

Question 15.
A man went door to door posing as a goldsmith. He promised to bring back the gliter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?
Answer:
The man must have dipped the gold bangles in the solution of aqua regia, a 3 : 1 mixture of concentrated HCl and concentrated HNO₃. Gold is soluble in aqua regia. After dipping the gold bangles in aqua regia the outer layer of gold gets dissolved and the inner shiny layer appears. That is why the weight of gold bangles reduced.

Question 16.
Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).
Answer:
The reactivity of copper metal is very low so it does not react with hot water and steam. Opposite to this iron present in steel reacts with steam so steel corrodes. So, copper is used to make hot water tanks and not steel.