Metals and nonmetals class 10 questions answers (Chapter 3)

This page contains Metals and nonmetals class 10 questions answers. Practice these questions for good grades in your exams. Other important links are provided at the bottom of the page.

Question 1 Give an example of a metal which

• is a liquid at room temperature.
• can be cut easily with a knife.
• is the best conductor of heat.
• is a poor conductor of heat.

Answer

• Metal that exists in the liquid state at room temperature – mercury
• Metal that can be easily cut with a knife- Sodium
• Metal that is the best conductor of heat- Silver
• Metal that is a poor conductor of heat – Mercury and Lead

Question 2 Why sodium is kept immersed in kerosene oil?

Answer Sodium is very reactive metal. It combines explosive with air as well as water. Hence, it catches fire if kept open. Therefore to prevent accidental fires and accident, sodium is stored immersed in kerosene oil.

Question 3 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 evolved when dilute hydrochloric acid is added to a reactive metal. When iron reacts with dilute H₂SO₄ then iron (ll) sulphate with the evolution of hydrogen gas is formed.

Fe(s) + H₂SO₄ (aq) —> FeSO₄(aq) + H₂(g)

Question 4 Why do ionic compounds have high melting points?

Answer Ionic compounds have strong electrostatic forces of attraction between the ions. Therefore, it requires a lot of energy to overcome these forces. That is why ionic compounds have high melting points.

 

Question 5 Which of following pairs give displacement reaction?

• NaCl solution and copper metal
• MgCl₂ solution and aluminium metal
• FeSO₄ solution and silver metal
• AgNO₃ solution and copper metal.

Answer AgNO₃ solution and copper metal.

Question 6 You are given a hammer, a battery, wires, and a switch.

(a) How could you use them to distinguish between samples of metals and non-metals?

(b) Assesses the usefulness of these tests in distinguishing between metals and non-metals.

Answer With the hammer, we can beat the sample and if it can be beaten into thin sheets (that is, it is malleable), then it is metal otherwise a non-metal. Similarly, we can use the battery, bulb, wires, and switch to set up a circuit with the sample. If the sample conducts electricity, then it is a metal otherwise a non-metal.

The above tests are useful in distinguishing between metal and non-metals in some cases but not all because there are exceptions also. These tests are based on physical properties and no chemical reactions are involved in these tests.

Question 7 What are amphoteric oxides? Give two examples of amphoteric oxides.

Answer Those oxides that behave as both acidic and basic oxides are called amphoteric oxides. Example: aluminum oxide (Al₂O₃) and zinc oxide (ZnO)

Question 8  Name two metals which will displace hydrogen from dilute acids, and two metals which not.

Answer Metals that are more reactive than hydrogen displace it from dilute acids. For example sodium and potassium. Metals that are less reactive than hydrogen do not displace it. For example copper and silver.

Question 9 Name a metal which is having low melting point and a non-metal having high melting point?

Answer Low melting point metal- Gallium

High melting point non-metal- diamond

Question 10 What is aqua regia? Which elements dissolve in it?

Answer Aqua regia is a mixture of HCl and HNO3 which is of ratio 3:1 in which chemical unreactive metal like gold and platinum dissolve in it.

Question 11 Give reasons:

1. Shining surface of metals is tarnished after some time.
2. The reaction of zinc with dilute nitric acid does not produce hydrogen gas.
3. Food cans are coated with tin rather than zinc.
4. Some alkali metals can be cut with a knife.

Answer 

1. Some metals like magnesium, aluminum, zinc etc., when exposed to air, form a protective layer of oxide on their surface. These layers prevent further corrosion of the metal.
2. Nitric acid is a strong oxidizing agent. It oxidized the produced hydrogen to water and itself reduced to NO, NO₂, N₂O.
3. Tin is less reactive metal than zinc. So it is not easily attacked by components of food items.
4. Due to high electropositive nature alkali of some metals are soft. They can be cut with the help of knife e.g. Li, Na, K.

Question 12 Define the following terms.

1. Mineral
2. Ore
3. Gangue

Answer

1. Mineral: The naturally occurring compounds or element in the earth’s crust are known as minerals.
2. Ore: Minerals from which the metal can be extracted profitably are known as ore
3. Gangue: The impurities (sand, silt, soil, gravel etc.) present in the ore are called gangue.

Question 13 What chemical process is used for obtaining a metal from its oxide?

Answer The chemical process for obtaining a metal from its oxide is a reduction. In this process, metal oxide are reduced by using suitable reducing agents such as carbon or by highly reactive metals to displace the metals from their oxides.

For example, zinc oxide is reduced to metallic zinc by heating with carbon.

ZnO(s) + C(s) —-> Zn(s) + CO(g)

Manganese dioxide is reduced to manganese by treating it with aluminum powder. In this case, aluminum displaces manganese from its oxide.

3MnO₂(s) + 4Al(s) —> 3Mn(l) + 2Al₂O₃ (s) + heat

Oxides of more reactive metals are reduced by electrolysis.

Question 14 Name two metals which will displace hydrogen from dilute acids, and two metals which not.

Answer Metals that are more reactive than hydrogen displace it from dilute acids. For example sodium and potassium. Metals that are less reactive than hydrogen do not displace it. For example copper and silver.

Question 15 Metallic oxides of Zinc, magnesium, and copper were heated with the following metals.

Metal                       Zinc                      Magnesium                  Copper

Zinc oxide                 –                              –

Magnesium oxide     –                              –                                       –

Copper oxide             –                              –

In which cases will you find displacement reaction taking place?

Answer

Metal                            Zinc oxide                     Magnesium oxide                     Copper oxide

Zinc                               No reaction                   No reaction                                Displacement

Magnesium                  Displacement                  No reaction                                Displacement

Copper                         No reaction                     No reaction                                 No reaction

Question 16 Give the reason as to why copper is used to make hot water tanks and not steel?

Answer Iron in steel is more reactive than copper. it reacts with steam and produces F3O4. This will make the tank weaker with time. On the other copper is less reactive which does not react with hot water. So, copper is used to make hot water tanks and not steel.

Question 17 Why ionic compounds are usually hard?

Answer They are solids and are somewhat hard because of the strong force of attraction between the positive and negative ions.

Question 18 Why non-metals do not displace hydrogen from dilute acids?

Answer Non-metals have less reactivity than hydrogen so they cannot displace hydrogen from dilute acids.

Question 19 Why ionic compounds are soluble in water?

Answer Ionic compounds are soluble in water because their oppositely charged ions break by the opposite pole of the water molecule?

Question 20 Why ionic compounds conduct electricity in the molten state?

Answer Ionic compounds conduct electricity in the molten state because the electrostatic forces of attraction between the oppositely charged ions are overcome due to heat.

Question 21  Justify the statement –‘all ores are minerals but all minerals are not ores’. Give one example which can be called both ore and minerals?

Answer Ore is the mineral from which a metal can be profitably or economically extracted. From each mineral, metal cannot be extracted profitably, so all minerals are not ores.

Examples: minerals- sodium chloride, magnesium chloride.

Question 22 What is thermite reaction?

Answer Thermite reaction involves a reaction between the aluminum metal and iron (III) oxide to form aluminum oxide and iron, releasing a large amount of heat.

$Fe_2O_3+2Al \rightarrow          2Fe     +     Al_2O_3     +    heat$

The thermite reaction is used in joining railway tracks, cracked machine parts that is why it is also called thermite welding.

Question 23 Can we take anode made up of pure metals and cathode made up of impure metals during electro-refining?

Answer No, an anode is made up of impure metal. On passing the current through the electrolyte, the pure metal from the dissolves into the electrolyte.

Question 24 Give reasons for the following:

1. Prior to the reduction of metal sulphides and metal, carbonates must be converted into metal oxides.
2. For extracting some metals, displacement reactions are used in place of carbon to obtain metals from their oxides.

Answer 

1. It is easier to obtain a metal from its oxide, as compared to its sulphides and carbonates.
2. The highly reactive metals i.e., sodium, calcium, aluminum etc. are used as reducing agents because they can displace metals of lower reactivity.

Question 25 What is meant by the concentration of ore? What is it necessary to concentrate an ore before processing?

Answer A process of removing unwanted impurities like sand, soil etc present in an ore (called gangue) is called concentration of ore. We need to concentrate the ore so that the earthly impurities do not interfere in the process of extraction.

Question 26 Metals like iron, silver, and copper get corroded on exposure to air. Write the chemical name of the substance deposited on their surface respectively with its color, in each case?

Answer Iron: iron oxide (brown)

Silver: silver sulphide (black)

Copper: basic copper carbonate (green)

Question 27 Why curd should not be kept in copper or brass vessels. What is done to protect it?

Answer Curd (acidic in nature) when kept in copper and brass container, corrodes and thus a layer of basic copper carbonate CuCO₃.Cu(OH)₂ is formed.

Question 28 Why aluminum vessels lose its shine readily?

Answer Moist air reacts with aluminum to form a strong but thin film of aluminum oxide on its surface which makes its metallic luster slightly dull. This process is called anodizing.

Question 29 Differentiate between roasting and calcination?

Roasting	Calcinations
In roasting, sulphide ore is strongly heated in the presence of air into metal oxide.	In calcinations, carbonate ore is strongly heated in absence of air into metal oxide.
For example, 2ZnS   +   3O2            2ZnO  +2SO2	For example, 2ZnCO3             ZnO  +  CO2

 Question 30 Define the term anode mud?

Answer The insoluble impurities which settle down at the bottom of the anode are known as anode mud.

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