Class 10 Science Chapter 3: Metals and Nonmetals (NCERT, SEBA, NBSE, TBSE etc.) focuses on the differences between metals and nonmetals. Understanding the distinctions between these two and how they behave in different contexts is crucial for students.
Get here the questions, answers, textbook solutions, PDF of Class 10 Science Chapter 3: Metals and Non-metals. In this chapter, you will learn the difference between metals and nonmetals, their use case, and how they are grouped based on their physical and chemical properties.
Intext I
1. Give an example of a metal which
(i) is a liquid at room temperature.
Answer: Mercury is a liquid at room temperature.
(ii) can be easily cut with a knife.
Answer: Sodium can be easily cut with a knife.
(iii) is the best conductor of heat.
Answer: Silver is the best conductor of heat.
(iv) is a poor conductor of heat.
Answer: Mercury and Lead are poor conductors of heat.
2. Explain the meanings of malleable and ductile.
Answer: Malleable refers to substances that can be beaten into thin sheets, such as most metals. Ductile refers to substances that can be drawn into thin wires, such as most metals.
Intext II
1. Why is sodium kept immersed in kerosene oil?
Answer: Sodium is highly reactive and can explosively react with oxygen, potentially catching fire. To prevent accidental damage, sodium is immersed in kerosene oil.
2. Write equations for the reactions of
(i) iron with steam
Answer: 3Fe (s) + 4H2O (g) → Fe3O4 (aq) + 4H2 (g)
(ii) calcium and potassium with water
Answer: Ca (s) + 2H2O (l) → Ca(OH)2 (aq) + H2 (g) + Heat
2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g) + Heat
3. Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows.
| Metal | Iron (II) sulphate | Copper (II) sulphate | Zinc sulphate | Silver nitrate |
| A | No Reaction | Displacement | ||
| B | Displacement | No Reaction | ||
| C | No Reaction | No Reaction | No Reaction | Displacement |
| D | No Reaction | No Reaction | No Reaction | Displacement |
Use the table above to answer the following questions about metals A, B, C and D.
(i) Which is the most reactive metal?
Answer: B is the most reactive metal.
(ii) What would you observe if B is added to a solution of copper (II) sulphate?
Answer: If B is added to a solution of copper (II) sulphate, you would observe displacement of copper by B.
(iii) Arrange the metals A, B, C and D in the order of decreasing reactivity.
Answer: The metals should be arranged in the following order of decreasing reactivity: B > A > C > D.
4. Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4.
Answer: Hydrogen gas is produced when dilute hydrochloric acid is added to a reactive metal. The chemical reaction when iron reacts with dilute H2SO4 is: Fe (s) + H2SO4 (aq) → FeSO4 (aq) + H2 (g)
5. What would you observe when zinc is added to a solution of iron (II) sulphate? Write the chemical reaction that takes place.
Answer: When zinc is added to a solution of iron (II) sulphate, you would observe displacement of iron by zinc. The chemical reaction that takes place is: Zn (s) + FeSO4 (aq) → ZnSO4 (aq) + Fe (s)
Intext III
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:
2. Why do ionic compounds have high melting points?
Answer: Ionic compounds have strong electrostatic forces of attraction between the ions, which requires a significant amount of energy to overcome. As a result, ionic compounds have high melting points.
Intext IV
1. Define the following terms.
(i) Mineral: A naturally occurring compound of elements.
(ii) Ore: A mineral from which metal can be extracted profitably.
(iii) Gangue: The impurities present in an ore, such as sand and rocks.
2. Name two metals that are found in nature in the free state.
Answer: Gold and silver are two metals that are found in nature in the free state.
3. What chemical process is used for obtaining a metal from its oxide?
Answer: The process of reduction is used to obtain a metal from its oxide.
Intext V
1. Metallic oxides of zinc, magnesium and copper were heated with the following metals.
| Metal | Zinc | Magnesium | Copper |
| Zinc oxide | |||
| Magnesium oxide | |||
| Copper oxide |
Answer:
| Metal | Zinc | Magnesium | Copper |
| Zinc oxide | No reaction | Displacement | No reaction |
| Magnesium oxide | No reaction | No reaction | No reaction |
| Copper oxide | Displacement | Displacement | No reaction |
2. Which metals do not corrode easily?
Answer: Silver and gold are metals that do not corrode easily due to their low reactivity.
3. What are alloys?
Answer: An alloy is a mixture of two or more metals, or a mixture of metals and non-metals. One example of an alloy is brass, which is a mixture of copper and zinc.
Exercise
1. Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal
(b) MgCl2solution and aluminium metal
(c) FeSO4solution and silver metal
(d) AgNO3solution and copper metal.
Answer: d) AgNO3solution and copper metal.
2. Which of the following methods is suitable for preventing an iron frying pan from rusting?
Answer: (c) Applying a coating of zinc
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:
Answer: (a) calcium
4. Food cans are coated with tin and not with zinc because:
Answer: (c) zinc is more reactive than tin.
5. You are given a hammer, a battery, a bulb, wires and a switch.
(a) How could you use the given materials to distinguish between samples of metals and non-metals?
Answer: To distinguish between samples of metals and non-metals, we can use the hammer to beat the sample and determine if it is malleable. If the sample is malleable, it is likely to be a metal. We can also use the battery, bulb, wires, and switch to set up a circuit with the sample. If the sample conducts electricity, it is likely to be a metal.
(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.
Answer: These tests are useful in distinguishing between metals and non-metals because they are based on physical properties and do not involve chemical reactions.
6. What are amphoteric oxides? Give two examples of amphoteric oxides.
Answer: Amphoteric oxides are oxides that behave as both acidic and basic oxides. Examples of amphoteric oxides include aluminium oxide (Al2O3) and zinc oxide (ZnO).
7. Name two metals that will displace hydrogen from dilute acids, and two metals that will not.
Answer: Iron and aluminium will displace hydrogen from dilute acids because they are more reactive than hydrogen. Mercury and copper will not displace hydrogen from dilute acids because they are less reactive than hydrogen.
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, the anode would be the impure metal M, the cathode would be a thin strip of pure metal M, and the electrolyte would be a solution of the salt of the metal M.
9. Pratyush 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?
Answer: (a) (i) There will be no action on dry litmus paper.
(ii) The colour of moist litmus paper will turn blue when exposed to a gas that is a non-metal oxide and red when exposed to a gas that is a basic oxide.
(b) Write a balanced chemical equation for the reaction taking place.
Answer: The balanced chemical equation for the reaction depends on the specific gas and the type of litmus paper that is being used. In general, the reaction of a gas with litmus paper will involve the transfer of protons or hydroxyl ions between the gas and the litmus paper.
10. State two ways to prevent the rusting of iron.
Answer: Two ways to prevent the rusting of iron are:
(a) Oiling, greasing, or painting the surface of the iron to create a barrier between the iron and the air, which will prevent moisture and oxygen from coming into contact with the iron and causing rust.
(b) Galvanization, which involves coating the iron with a layer of zinc metal, which is more reactive than iron and will protect the iron from coming into contact with oxygen and moisture.
11. What happens to potassium and sodium if they are kept in open? Why are they immersed in kerosene?
Answer: Potassium and sodium are highly reactive metals that will catch fire when left in the open, due to their strong affinity for oxygen. To protect these metals and prevent accidental fires, they are typically kept immersed in kerosene oil.
(a) ‘Sodium is a highly reactive metal and it cannot be obtained from its oxide by heating with carbon’. Give reason.
Answer: Sodium is a highly reactive metal that has a strong affinity for oxygen. As a result, it cannot be reduced by carbon or any other reducing agent. When sodium is heated with carbon, the carbon reacts with the oxygen present in the sodium oxide rather than reducing the oxide to metal.
(b) How can sodium be obtained from sodium chloride?
Answer: Sodium can be obtained from sodium chloride through a process called electrolytic reduction. In this process, the sodium chloride is melted and then electrolysed. During electrolysis, sodium is deposited at the cathode (- charged electrode) and chlorine is liberated at the anode (+ electrode). The balanced chemical equations for these reactions are:
At cathode: Na+ + e- → Na
At anode: 2Cl- → Cl2 + 2e-
12. A metal ‘E’ is stored under kerosene oil. When a small piece of it is left open in the air, it catches fire. When the product formed is dissolved in water, it turns red litmus blue.
(i) Name the metal E.
Answer: The metal is sodium.
(ii) Write the chemical equation for the reaction when it is exposed to air and when the product is dissolved in water.
Answer: When sodium is exposed to air, it reacts with oxygen to form sodium oxide. The balanced chemical equation for this reaction is:
4Na + O2 → 2Na2O
When the product is dissolved in water, it reacts to form sodium hydroxide. The balanced chemical equation for this reaction is:
Na2O + H2O → 2NaOH
(iii) Explain the process by which the metal is obtained from its molten chloride.
Answer: Sodium can be obtained from its molten chloride (sodium chloride) through a process called electrolysis. In this process, the sodium chloride is melted and then electrolysed. During electrolysis, sodium is deposited at the cathode (- charged electrode) and chlorine is liberated at the anode (+ electrode). The balanced chemical equations for these reactions are:
At cathode: Na+ + e- → Na
At anode: 2Cl- → Cl2 + 2e-
14. Most metal oxides are insoluble in water, but some of these dissolve in water. What are these oxides and their solution in water called?
Answer: These oxides are called basic oxides, and their solutions in water are called alkalis. Basic oxides are oxides that have a low affinity for protons and can accept protons from water molecules. When a basic oxide is dissolved in water, it forms an alkali solution, which is characterized by its ability to turn red litmus paper blue and to neutralize acids. Some examples of basic oxides include calcium oxide, magnesium oxide, and barium oxide.
15. How can metals be differentiated from non-metals based on any three chemical properties?
Answer: Three chemical properties that can be used to differentiate metals from non-metals are:
Metal: Metals are electropositive, meaning they have a positive charge and are attracted to the negative electrode during electrolysis.
Non-metal: Non-metals are electronegative, meaning they have a negative charge and are attracted to the positive electrode during electrolysis.
Metal: The oxides of metals are basic, meaning they have a low affinity for protons and can accept protons from water molecules.
Non-metal: The oxides of non-metals are acidic, meaning they have a high affinity for protons and can donate protons to water molecules.
Metal: Metals can displace hydrogen from dilute acids, meaning they are more reactive than hydrogen and can replace it in a chemical reaction.
Non-metal: Non-metals cannot replace hydrogen from dilute acids, meaning they are less reactive than hydrogen.
16. Give a reason for the following:
(a) Aluminum sheets do not corrode easily.
Answer: Aluminum sheets do not corrode easily because when aluminum reacts with air, it forms a thin layer of aluminum oxide on the surface. This oxide layer is very stable and prevents further reaction of aluminum with oxygen.
(b) Copper vessels are covered with a green coating in the rainy season.
Answer: Copper vessels turn green in the rainy season due to the formation of copper carbonate. Copper carbonate is formed by the reaction of copper with carbonic acid, which is present in acid rain.
17. What type of oxides are formed when non-metals combine with oxygen?
Answer: When non-metals combine with oxygen, they form either neutral or acidic oxides. Neutral oxides are those that do not have a significant acid or base character, while acidic oxides have a high affinity for protons and can donate protons to water molecules. Examples of acidic oxides include NO2 (nitrogen dioxide) and SO2 (sulfur dioxide), while examples of neutral oxides include NO (nitric oxide) and CO (carbon monoxide).
18. Give reasons for the following:
(a) Platinum, gold, and silver are used to make jewelry.
Answer: Platinum, gold, and silver are used to make jewelry because they are very lustrous and have a high value. They are also very unreactive and do not corrode easily, making them suitable for use in jewelry.
(b) Sodium, potassium, and lithium are stored under oil.
Answer: Sodium, potassium, and lithium are very reactive metals and react very vigorously with air as well as water. Therefore, they are kept immersed in oil in order to prevent their contact with air and moisture and to protect them from accidental fires.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
Answer: Despite being a highly reactive metal, aluminium is resistant to corrosion due to the formation of a stable oxide layer on its surface. It is also light in weight and a good conductor of heat, making it suitable for use in cooking utensils.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
Answer: Carbonate and sulphide ores are usually converted into oxides during the process of extraction because metals can be more easily extracted from their oxides rather than from their carbonates and sulphides.
19. You have probably seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
Answer: Copper vessels become tarnished due to the formation of a layer of copper carbonate on the surface. Copper carbonate is formed by the reaction of copper with moist carbon dioxide in the air. The citric acid present in lemon or tamarind juice is able to neutralize the basic copper carbonate and dissolve the layer, revealing the shiny copper surface underneath. This is why these sour substances are effective in cleaning tarnished copper vessels.
20. Differentiate between metal and non-metal on the basis of their chemical properties.
Answer: Metal and non-metal can be differentiated based on their chemical properties as follows:
- Metals are electropositive, while non-metals are electronegative.
- Oxides of metals are basic in nature, while oxides of non-metals are acidic.
- Metals can displace hydrogen from dilute acids, while non-metals cannot.
- Metals form chlorides that are electrovalent or ionic compounds, while non-metals form covalent chlorides.
- Metals react with water to form oxides and hydroxides, while non-metals do not react with water.
21. A man went door to door posing as a goldsmith. He promised to bring back the glitter 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 posing as a goldsmith used Aqua regia, a mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1, to bring back the shine of old and dull gold ornaments. This solution is capable of dissolving metals like gold and platinum, and the weight of the gold bangles was reduced drastically because the outer layer of the bangles was dissolved in the solution.
22. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).
Answer: Copper is used to make hot water tanks because it does not react with cold water, hot water, or steam. In contrast, iron reacts with steam, and if hot water tanks were made of steel (an alloy of iron), the iron would react vigorously with the steam formed from hot water. Therefore, copper is a better choice for hot water tanks than steel.
Tick (✓) the correct option
1. Silver articles become black on prolonged exposure to air. This is due to the formation of:
Answer: (c) Ag2s
2. The metals which are mixed with iron to make stainless steel are:
Answer: (b) nickel and chromium
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:
Answer: (a) calcium
4. An element A is soft and can be cut with a knife. This is very reactive to air and cannot be kept open in air. It reacts vigorously with water. Identify the element from the following:
Answer: (b) Na
5. Bronze is an alloy of:
Answer: (a) Cu and Zn
6. Galvanization is a method of protecting:
Answer: (c) steel and iron from rusting
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