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

Question 1. Give an example of a metal which
1. Is a liquid at room temperature
2. Can be easily cut with knife.
3. Is the best conductor of heat
4. Is a poor conductor of heat.
Answer:
1. Mercury (Hg) is a liquid at room temperature.
2. Sodium and potassium can be easily cut with a knife.
3. Silver is considered the best conductor of heat.
4. Lead is a poor conductor of heat.
In simple words: This question asks for specific metals based on their properties. Mercury is liquid, sodium/potassium are soft, silver conducts heat best, and lead conducts heat poorly.

Exam Tip: Remember these unique properties of metals as they are common short-answer questions. Mercury is the only metal liquid at room temperature, and sodium/potassium are exceptions to metal hardness.

Question 2. Explain the meanings of malleable and ductile.
Answer:
1. Malleable: A metal is called malleable if it can be beaten into thin sheets. For instance, silver and gold are excellent malleable metals.
2. Ductile: A metal is called ductile when it can be drawn into thin wires. Silver and gold are also prime examples of ductile metals.
In simple words: Malleable means you can hammer a metal into flat sheets without it breaking. Ductile means you can stretch a metal into long, thin wires.

Exam Tip: These are key physical properties of metals. Understanding them helps distinguish metals from non-metals. Gold and silver are highly malleable and ductile due to their atomic structure.

Question 3. Why is sodium kept immersed in kerosene oil?
Answer: Sodium is a highly reactive metal. It reacts vigorously with oxygen in the air at room temperature, and this reaction is highly exothermic, producing a lot of heat. To prevent this strong reaction, sodium is stored under kerosene. Sodium does not react with kerosene.
In simple words: Sodium is very active and quickly reacts with air, even catching fire. Keeping it in kerosene oil stops it from touching the air and reacting.

Exam Tip: Always remember that highly reactive metals like sodium and potassium must be stored away from air and moisture to prevent dangerous reactions.

Question 4. Write equations for the reactions of
1. Iron with steam
2. Calcium and potassium with water
Answer:
1. Iron with steam
\( 3Fe(s) + 4H_2O(g) \longrightarrow Fe_3O_4(s) + 4H_2(g) \)
2. Calcium and potassium with water
\( Ca(s) + 2H_2O(l) \longrightarrow Ca(OH)_2(aq) + H_2(g) \)
\( 2K(s) + 2H_2O(l) \longrightarrow 2KOH(aq) + H_2(g) \)
In simple words: These equations show how iron reacts with steam, and how calcium and potassium react with cold water to produce hydrogen gas.

Exam Tip: Pay attention to the states of matter (s, l, g, aq) in chemical equations. Also, remember that different metals react with water at different temperatures (cold water, hot water, or steam).

Question 5. 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.
1. Which is the most reactive metal?
2. What would you observe if B is added to a solution of copper (II) sulphate?
3. Arrange the metals A, B, C and D in the order of decreasing reactivity.
Answer:
1. Metal B is the most reactive.
2. If metal B is added to a solution of copper (II) sulphate, the blue color of the copper sulphate solution would disappear, and reddish-brown copper metal would be deposited on metal B.
3. The order of decreasing reactivity for the metals is B > A > C > D.
In simple words: Metal B is the most active. If you put metal B in copper sulphate, the blue color goes away and copper appears. The metals arranged from most active to least active are B, then A, then C, then D.

Exam Tip: In reactivity series questions, remember that a more reactive metal displaces a less reactive metal from its salt solution. This principle helps determine the relative reactivity of unknown metals.

Question 6. Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute \( H_2SO_4 \).
Answer: When a reactive metal reacts with dilute hydrochloric acid, hydrogen gas is produced. A reactive metal displaces the hydrogen from the acid, leading to the release of hydrogen gas.
\( Fe(s) + dil. H_2SO_4(aq) \longrightarrow FeSO_4(aq) + H_2(g) \)
In simple words: When a strong metal mixes with weak acid, hydrogen gas comes out. For example, iron reacting with sulfuric acid makes iron sulfate and hydrogen gas.

Exam Tip: Remember that hydrogen gas is typically produced when a metal reacts with an acid. You can test for hydrogen gas with a burning splinter, which will extinguish with a 'pop' sound.

Question 7. 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 than iron. Therefore, when zinc is added to iron (II) sulphate, it displaces the iron metal. The solution's color fades from green to colorless due to the formation of zinc sulphate. Additionally, greyish-black iron metal gets deposited.
\( Zn(s) + FeSO_4(aq) \longrightarrow ZnSO_4(aq) + Fe(s) \)
(pale green) (colorless)
In simple words: When zinc goes into iron sulfate, the green liquid turns clear, and dark iron bits show up. This happens because zinc is stronger than iron and pushes it out of the solution.

Exam Tip: Displacement reactions are common. Always compare the reactivity of the metals involved to predict the outcome and associated visual changes (like color change or precipitate formation).

Question 8.
(i) Write the electron dot structures for sodium, oxygen and magnesium.
(ii) Show the formation of \( Na_2O \) and \( MgO \) by the transfer of electrons.
(iii) What are the ions present in these compounds?
Answer:
(i) Electron dot structures:

(iii) The ions present in \( Na_2O \) are \( Na^+ \) and \( O^{2-} \). The ions present in \( MgO \) are \( Mg^{2+} \) and \( O^{2-} \).
In simple words: Part (i) shows the tiny dots (electrons) around sodium, oxygen, and magnesium atoms and what they look like after gaining or losing electrons to become ions. Part (ii) illustrates how atoms transfer electrons to form compounds like \( Na_2O \) and \( MgO \). Part (iii) identifies the charged particles, or ions, found in these compounds.

Exam Tip: Electron dot structures are crucial for understanding ionic and covalent bonding. Remember that metals tend to lose electrons to form positive ions (cations), while non-metals tend to gain electrons to form negative ions (anions).

Question 9. Name two metals which are found in nature in free state.
Answer: Gold, platinum, and silver are metals found in nature in their free, uncombined state.
In simple words: Gold, platinum, and silver are metals you can find as pure metal in the ground, not mixed up in rocks.

Exam Tip: Unreactive metals, those low in the reactivity series, are typically found in their free state because they do not readily combine with other elements.

Question 10. What chemical process is used for obtaining a metal from its oxide?
Answer: To obtain metals from their oxides, several chemical processes are used depending on the metal's reactivity. For metals of medium reactivity, carbon can be employed as a reducing agent, and this chemical process is termed reduction. Additionally, a displacement reaction can be used where a highly reactive metal acts as the reducing agent. However, for highly reactive metals, the method of electrolytic reduction is used.
Example: \( 3MnO_2(s) + 4Al(s) \longrightarrow 3Mn(l) + 2Al_2O_3(S) + heat \)
In simple words: To get a metal out of its oxide, we use a process called reduction. For less active metals, we can use carbon to pull out the oxygen. For very active metals, we use electricity.

Exam Tip: The choice of reduction method depends on the reactivity of the metal. Electrolytic reduction is energy-intensive but necessary for highly reactive metals like sodium and aluminium.

Question 12. Metallic oxides of zinc, magnesium and copper were heated with the following metals.

In which cases will you find displacement reactions take place?
Answer:

Displacement reactions will happen in the cases shown in the table: Magnesium displaces Zinc from zinc oxide, Zinc displaces Copper from copper oxide, and Magnesium displaces Copper from copper oxide.
In simple words: A metal will replace another metal from its oxide if it's more reactive. The table shows where this "swapping" of metals will occur.

Exam Tip: To predict displacement reactions, you must know the reactivity series. A metal higher in the series can displace a metal lower in the series from its compound.

Question 13. Which metals do not corrode easily?
Answer: Metals that are less reactive and are positioned at the bottom of the reactivity series, such as silver, gold, and platinum, do not readily react with atmospheric gases. As a result, they do not corrode easily.
In simple words: Metals like silver, gold, and platinum don't rust or tarnish easily because they aren't very reactive with air or water.

Exam Tip: The noble metals (gold, platinum, silver) are valued for their resistance to corrosion, which is why they are used in jewelry and for other durable applications.

Question 14. What are alloys?
Answer: Alloys are homogeneous mixtures of two or more metals, or a metal and a non-metal.
Example:
Brass - \( Cu + Zn \) metal + metal
Bronze - \( Cu + Sn \) metal + metal
Steel - \( Fe + Ni + Cr + C \) metals + non-metal
In simple words: Alloys are special mixtures made by combining two or more metals, or a metal with a non-metal, to create a new material with better properties.

Exam Tip: Understanding alloys is important as they often have properties superior to their individual constituent elements, such as increased strength or corrosion resistance.

In-Text Activities Solved

Activity 3.1
Answer: Take samples of iron, copper, aluminium, and magnesium. The surface of these metals often appears dull. When rubbed with sandpaper, they reveal a shiny surface. This characteristic is called lustre.
In simple words: When you rub metals like iron or copper with sandpaper, they get shiny. This shine is called lustre.

Exam Tip: Lustre is a key physical property of metals. Always try to link observed properties to the definition when explaining activities.

Activity 3.2
Answer: Among small pieces of iron, copper, aluminium, magnesium, and sodium, only sodium and magnesium metal can be cut with a knife. All the other metals are hard.
In simple words: From a group of metals, only sodium and magnesium are soft enough to be cut with a knife; the rest are hard.

Exam Tip: Remember that hardness is a typical property of metals, but there are exceptions like sodium and potassium, which are soft.

Activity 3.3
Answer: Take iron, zinc, lead, and copper and hammer them. The metals will change their shape, becoming flattened into thin sheets. This ability of metals is known as malleability.
In simple words: If you hammer metals like iron, they flatten into thin sheets. This ability is called malleability.

Exam Tip: Malleability is a distinguishing physical property of metals. Be ready to give examples of malleable metals.

Activity 3.4
Answer: Metals like iron, copper, aluminium, and lead demonstrate the property called ductility. This means these metals can be drawn into wires.
In simple words: Metals such as iron and copper can be pulled into long, thin wires. This ability is called ductility.

Exam Tip: Ductility is another characteristic property of metals, essential for applications like electrical wiring. Gold is one of the most ductile metals.

Activity 3.5
Answer:
1. Take an aluminium or copper wire. Secure it on a clamp stand as shown in the figure. Attach a pin to the free end of the wire using wax.
2. Heat the wire with a burner at the other end. After some time, the pin drops.
3. This experiment shows that metals conduct heat.

In simple words: This experiment shows that metals are good at carrying heat. When one end of a metal wire is heated, the heat travels along the wire, melting the wax and making the pin drop.

Exam Tip: Heat conduction in metals is due to the presence of free electrons. This activity is a classic demonstration of this property.

Activity 3.6
Answer: This activity involves setting up a circuit with a battery, switch, and bulb to test the electrical conductivity of various materials. When a metal sample is placed between terminals A and B, the bulb glows, indicating that the metal is a good conductor of electricity.

Metals are good conductors of electricity.
In simple words: When you connect a metal sample into a simple electric circuit with a battery and bulb, the bulb lights up. This proves that metals can carry electricity well.

Exam Tip: Electrical conductivity in metals is also due to free electrons. This property is vital for electrical wiring and electronic components.

Activity 3.7
Answer: Samples of carbon (coal or graphite), sulphur and iodine.

In simple words: This table compares properties of non-metals like carbon, sulfur, and iodine. It shows how they differ from metals in terms of shine, hardness, and ability to conduct heat or electricity. Graphite is an exception for conductivity.

Exam Tip: Remember that non-metals generally lack lustre, malleability, ductility, and conductivity, with graphite (a form of carbon) being a notable exception for electrical conductivity.

Activity 3.8
Answer:
1. Take a magnesium ribbon, rub it, and then burn it. The resulting white ashes are dissolved in water. The solution obtained turns red litmus paper blue but does not change the color of blue litmus paper. This indicates that magnesium on burning forms magnesium oxide, which is basic in nature.
2. Take sulphur powder, burn it in a test tube, and collect the fumes produced in another test tube. Add some water to this test tube and shake it. The resulting solution turns blue litmus red but does not change the color of red litmus paper.
3. This shows that sulphur on heating produces sulphur dioxide, which is acidic in nature. The conclusion is that metal oxides are typically basic in nature, while non-metal oxides are typically acidic in nature.
In simple words: Burning magnesium makes a basic oxide that turns red litmus blue. Burning sulfur makes an acidic oxide that turns blue litmus red. So, metal oxides are usually basic, and non-metal oxides are usually acidic.

Exam Tip: Always remember the general rule: metal oxides are basic, and non-metal oxides are acidic. Litmus paper is a simple indicator to test for these properties.

Activity 3.9
Answer: Burn metals with the help of a pair of tongs to record the following observations:

Conclusion: Sodium reacts strongly with oxygen; it even catches fire if left open in the air. Magnesium and Calcium react less quickly with oxygen. Iron, Aluminium, and Zinc react slowly with oxygen. Copper did not burn but formed a black coating of \( CuO \).
In simple words: Different metals burn differently and some react with oxygen more than others. Sodium burns very strongly, while copper just forms a black layer. These observations help us understand how reactive each metal is.

Exam Tip: The color of the flame and the burnt metal, along with solubility, provide clues about the metal's reactivity and the nature of its oxide. Remember the exceptions for flame colors.

Activity 3.10
Answer: Place samples of small pieces of metals in beakers half-filled with cold water.
1. Metals that reacted with cold water: Na, K and Ca.
2. Metals that produced fire: Na and K.
3. Metals that started floating after some time: Ca and Mg.
4. Metals that reacted with hot water: Mg.
5. Metals that reacted with steam: Al, Zn and Fe.
6. Metals that did not react with steam: Pb, Cu, Ag and Au.
7. Reactivity of Metals: K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu > Hg > Ag > Au
In simple words: This activity shows how different metals react with water at different temperatures. Some metals react with cold water, some with hot water, and some only with steam. The results help us put metals in order of how reactive they are.

Exam Tip: The reactivity series is fundamental to understanding metal reactions. Metals higher in the series react more vigorously with water and acids.

Activity 3.11
Answer:

In simple words: This table shows how quickly different metals react with weak hydrochloric acid. Magnesium reacts very fast, aluminium and zinc are fast, iron is slow, and copper doesn't react at all. This helps us see how reactive each metal is.

Exam Tip: The rate of reaction with dilute acids is another way to compare metal reactivity. Hydrogen gas is released during these reactions.

Activity 3.12. Explain the common observation in various reactivity experiments.
Answer: Activity 3.12 likely involves observing the reactivity of different metals with various substances. In such experiments, a common observation is that the more reactive a metal is, the more vigorously it reacts. This can manifest as faster gas production, more intense heat generation, or a more pronounced color change in solutions. Conversely, less reactive metals will show little to no reaction under similar conditions. These observations allow for the establishment of a metal reactivity series.
In simple words: In experiments, you usually see that some metals react strongly and quickly, while others react slowly or not at all. This helps scientists put metals in order from most active to least active.

Exam Tip: When describing observations in reactivity experiments, always be specific about the signs of reaction (e.g., bubbles, heat, color change, precipitate formation).

Activity 3.13
Answer: Take samples of sodium chloride, potassium iodide, and barium chloride and record the following observations:

In simple words: This table compares some salts like salt, potassium iodide, and barium chloride. It shows they are solids, have specific flame colors when heated, dissolve in water but not in petrol, and can carry electricity.

Exam Tip: Ionic compounds (salts) are typically solid, water-soluble, and conductors of electricity in molten state or solution, but not in solid state.

Activity 3.14
Answer: The given setup of 3 test tubes A, B and C is shown below.

The iron nails in test tube A rust. The iron nails in test tube B and C do not rust.
Reason: Nails in test tube A are exposed to both air and water. Nails in test tube B do not get exposed to air due to the layer of oil. Nails in test tube C do not get both air and water.
Conclusion: Both air and water are needed for iron nails to rust.
In simple words: This experiment uses three test tubes to show how rust forms on iron nails. Test tube A has both air and water, so the nail rusts. Test tube B has oil on top of water, stopping air contact, so no rust. Test tube C has a drying agent to remove moisture, so no rust there either. This proves that both air and water are necessary for iron to rust.

Exam Tip: This is a standard experiment to demonstrate the conditions for rusting. Clearly explain why each setup (A, B, C) behaves the way it does to score full marks.

Gujarat Board Class 10 Science 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 silver metal
(d) AgNO3 solution and copper metal
Answer: (d) AgNO3 solution and copper metal
(a) Copper cannot displace Na \( \longrightarrow \) No reaction
(b) Aluminium cannot displace Mg \( \longrightarrow \) No reaction
(c) Silver cannot displace Fe \( \longrightarrow \) No reaction
(d) Copper can displace Ag \( \longrightarrow \) Reaction takes place
In simple words: Copper is more reactive than silver, so it can push silver out of its salt solution. In all other options, the metal is less reactive than the metal in the solution, so no reaction happens.

Exam Tip: To answer displacement reaction questions, always refer to the reactivity series. A more reactive metal will displace a less reactive metal from its salt solution.

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 options
Answer: (c) Applying a coating of zinc
In simple words: Putting a layer of zinc on an iron pan is the best way to stop it from rusting. This is called galvanization.

Exam Tip: Galvanization (coating with zinc) offers better protection than grease or paint because zinc is more reactive than iron and provides sacrificial protection.

Question 3. An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. This element is likely to be –
(a) calcium
(b) carbon
(c) silicon
(d) iron
Answer: (a) Calcium.
In simple words: Calcium reacts with oxygen to form calcium oxide, which has a high melting point and dissolves in water. This fits the description given.

Exam Tip: Recall that metal oxides typically have high melting points and some, especially those of alkali and alkaline earth metals, are soluble in water (forming hydroxides).

Question 4. Food cans are coated with tin and not with zinc because –
(a) zinc is costlier than tin.
(b) zinc has 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.
In simple words: Food cans use tin as a coating instead of zinc because zinc reacts more easily with food than tin does.

Exam Tip: The reactivity of the coating metal is critical for food containers. A less reactive metal like tin is preferred to prevent undesirable reactions with food contents.

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) To distinguish between samples of metals and non-metals, one can use a hammer to beat the given material into sheets. If it breaks, it is a non-metal, but if it can be beaten into thin sheets, it is a metal. One can also use a battery, wires, a bulb, and a switch to construct a circuit. Use the given material to complete the circuit one by one. If the electric current flows and the bulb glows, it is a metal; if not, then it is a non-metal.

(b) Although these tests provide general ideas for distinguishing between metals and non-metals, they are not completely reliable because there are exceptions in both categories. For example, sodium metal is brittle, and graphite can demonstrate conductivity.
In simple words: (a) You can hit a material with a hammer: if it flattens, it's metal; if it breaks, it's non-metal. You can also test if it conducts electricity using a battery, bulb, and wires. (b) These tests are mostly helpful but not always perfect, as some metals can be brittle and some non-metals can conduct electricity.

Exam Tip: When differentiating between metals and non-metals, consider both physical properties (malleability, ductility, lustre, hardness) and electrical conductivity, but be aware of exceptions to these general rules.

Question 6. What are amphoteric oxides? Give two examples of amphoteric oxides.
Answer: Amphoteric oxides are oxides that show both acidic and basic behavior. They react with acids as well as bases to form salts and water.
Examples of amphoteric oxides are \( Al_2O_3 \) and \( ZnO \).
Example: \( Al_2O_3 + 6HCl \longrightarrow 2AlCl_3 + 3H_2O \)
\( Al_2O_3 + 2NaOH \longrightarrow 2NaAlO_2 + H_2O \)
In simple words: Amphoteric oxides are special oxides that can act as both an acid and a base. This means they can react with both acids and bases to make salt and water. Aluminium oxide and zinc oxide are good examples.

Exam Tip: Remember the two examples, \( Al_2O_3 \) and \( ZnO \), and be able to write balanced chemical equations demonstrating their dual acidic and basic nature.

Question 7. Name two metals which will displace hydrogen from dilute acids and two metals which will not.
Answer: Metals positioned above hydrogen in the activity series, such as zinc (Zn), aluminium (Al), and magnesium (Mg), can displace hydrogen from dilute acids because they are more reactive than \( H_2 \). Metals positioned below hydrogen in the activity series, such as copper (Cu), silver (Ag), and gold (Au), cannot displace hydrogen from dilute acids because they are less reactive than hydrogen.
In simple words: Metals that are more active than hydrogen (like zinc and aluminium) can push hydrogen out of weak acids. Metals that are less active than hydrogen (like copper and silver) cannot.

Exam Tip: The position of hydrogen in the reactivity series is a crucial reference point. Metals above hydrogen react with acids to produce hydrogen gas, while those below do not.

Question 8. In the electrolytic refining of M, what would you take as the anode, the cathode and the electrolyte?
Answer: In the electrolytic refining of metal M:
Anode \( \longrightarrow \) Impure metal M
Cathode \( \longrightarrow \) Pure sample of metal M
Electrolyte \( \longrightarrow \) Acidified, soluble salt of metal M
In simple words: To make a metal purer using electricity, you put the impure metal at the anode, a pure piece of the metal at the cathode, and a liquid solution of that metal's salt as the electrolyte.

Exam Tip: Remember that during electrolytic refining, the impure metal at the anode gradually dissolves, while the pure metal deposits on the cathode. Impurities settle as anode mud.

Question 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?
(b) Write the balanced chemical equation for the reaction taking place.
Answer:
(a) (i) There will be no effect of the gas on dry litmus paper.
(ii) Moist blue litmus paper turns red.

(b) (i) \( S + O_2 \longrightarrow SO_2 \)
(ii) \( SO_2 + H_2O \longrightarrow H_2SO_3 \) (sulphurous acid)
In simple words: (a) When sulphur gas is tested, it won't change dry litmus paper, but it will turn moist blue litmus paper red because it forms an acid with water. (b) This shows that sulphur burns in oxygen to make sulphur dioxide gas, which then mixes with water to form sulphurous acid.

Exam Tip: Non-metal oxides like sulphur dioxide are acidic. They turn moist blue litmus paper red because they react with water to form acids. Remember the balanced chemical equations.

Question 10. State two ways to prevent the rusting of iron.
Answer:
1. Rusting can be prevented by painting iron articles, which ensures the iron surface does not come into contact with the air and moisture needed for rusting.
2. By coating iron articles with a protective layer of zinc metal, a process known as galvanization, which successfully prevents the rusting of iron.
In simple words: You can stop iron from rusting by either painting it or by covering it with a layer of zinc, which is called galvanization. Both methods keep air and water away from the iron.

Exam Tip: Painting is a simple method, but galvanization offers better protection due to the sacrificial protection provided by zinc. Be prepared to explain both methods and their advantages.

Question 11. What type of oxides are formed when non-metals combine with oxygen?
Answer: When non-metals combine with oxygen, they generally form acidic oxides. For example, \( SO_2, CO_2, NO_2 \). In some cases, they can also form neutral oxides, such as \( H_2O \) and \( CO \).
In simple words: When non-metals join with oxygen, they usually make acidic oxides. Sometimes, they can also make neutral oxides.

Exam Tip: Remember the general rule that non-metal oxides are acidic, and be ready to provide examples for both acidic and neutral non-metal oxides.

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 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) Gold (Au), silver (Ag), and platinum (Pt) are highly lustrous, malleable, and ductile. They are also among the least reactive metals. These properties make them ideal for crafting jewelry.
(b) Sodium (Na), potassium (K), and lithium (Li) are highly reactive metals. They react intensely with oxygen present in the air at room temperature and can catch fire in the presence of moisture. They do not react with oil (kerosene), which is why they are stored under it.
(c) Aluminium is a highly reactive metal, but it forms a protective layer of aluminium oxide \( (Al_2O_3) \) on its surface. This layer shields it from corrosion and further reaction with food items, making it suitable for cooking utensils.
(d) Reducing metal oxides to metal is simpler and less costly than reducing carbonate and sulphide ores directly. Therefore, carbonate and sulphide ores are first changed into metal oxide and then reduced to form metals.
In simple words: (a) Platinum, gold, and silver are shiny, easy to shape, and don't react much, making them perfect for jewelry. (b) Sodium, potassium, and lithium are very active and catch fire easily, so they are kept in oil to stop them from touching air or water. (c) Aluminium is active, but it forms a protective layer that stops it from corroding, so it's good for cooking. (d) It's easier and cheaper to get metals from their oxides, so carbonate and sulfide ores are first changed into oxides before getting the pure metal.

Exam Tip: For 'reason' questions, clearly state the property or fact and then explain its consequence. Link properties like reactivity, malleability, and oxide formation to the specific uses or storage methods of the metals.

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 metal corrodes to form copper carbonate, which appears as a green tarnish on the vessels. When cleaned with lemon or tamarind juice, the acids present in these substances dissolve the copper carbonate, thereby effectively cleaning the vessel.
In simple words: Copper vessels turn green because they form copper carbonate. Lemon or tamarind juice contains acid, which dissolves this green layer, making the vessels clean again.

Exam Tip: This question relates to the basic nature of metal carbonates and their reaction with acids. The acid in the fruit juice neutralizes the basic copper carbonate.

Question 14. Differentiate between metal and non-metal on the basis of their chemical properties.
Answer: Here are the differences between metals and non-metals based on their chemical characteristics:
**Metal:**
- Metals give up electrons to make positive ions.
- Metals create basic oxides.
- Metals are able to remove hydrogen from acids.
- Not all metals join with hydrogen to create hydrides (only active metals such as Na, K, Ca do).
**Non-metal:**
- Non-metals take in electrons to form negative ions.
- Non-metals make acidic oxides. They cannot remove hydrogen from acids.
- All non-metals join with hydrogen to make hydrides.
In simple words: Metals tend to lose electrons, form basic oxides, and can displace hydrogen from acids, while non-metals gain electrons, form acidic oxides, and cannot displace hydrogen from acids.

Exam Tip: Remember to clearly state the chemical property and how metals and non-metals differ in that specific aspect.

Question 15. 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 goldsmith used a solution called aqua regia. This solution is a mix of one part strong nitric acid (\( HNO_3 \)) and three parts strong hydrochloric acid (\( HCl \)). It can easily dissolve gold, which explains why the bangles lost weight but looked shiny.
In simple words: The goldsmith used aqua regia, a strong acid mix, which dissolved some of the gold, making the jewelry lighter but shiny.

Exam Tip: Aqua regia is a potent mixture known for its ability to dissolve noble metals like gold, a key fact for this type of problem.

Question 16. Why are hot water tanks made of copper and not steel?
Answer: Copper helps make hot water tanks as it does not react with any type of water, even steam. It is also affordable, easily found, and conducts heat well, which makes it a better choice than steel, which can rust.
In simple words: Copper is good for water tanks because it doesn't rust, is common, and conducts heat well, unlike steel.

Exam Tip: Consider reactivity with water, availability, and thermal conductivity when choosing metals for water heating applications.

Gujarat Board Class 10 Science Metals and Non-metals Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1. Define metals.
Answer: Elements that give up electrons to become positive ions are called metals.
In simple words: Metals are elements that lose electrons to form positive ions.

Exam Tip: Focus on the electron loss and positive ion formation as the defining characteristic of metals.

Question 2. Name a metal which can be cut with knife.
Answer: Sodium is a metal that can be easily cut with a knife.
In simple words: Sodium can be cut with a knife.

Exam Tip: Sodium and potassium are notable exceptions to the general hardness of metals, making them important to remember.

Question 3. Name two metals which do not react with oxygen.
Answer: Gold and silver are two metals that do not react with oxygen.
In simple words: Gold and silver do not react with oxygen.

Exam Tip: These are noble metals, known for their low reactivity and resistance to corrosion.

Question 4. What type of oxides are formed when metals combine with oxygen?
Answer: When metals mix with oxygen, they create basic oxides.
In simple words: Metals form basic oxides when they react with oxygen.

Exam Tip: Remember that non-metals generally form acidic oxides, providing a good point of comparison.

Question 5. Name two metals which are best conductors of heat.
Answer: Silver and copper are two metals that conduct heat most effectively.
In simple words: Silver and copper are the best heat conductors.

Exam Tip: Silver is the best conductor of both heat and electricity, followed closely by copper for electrical conductivity.

Question 6. Name two metals which are poor conductors of heat.
Answer: Lead and mercury are two metals that do not conduct heat well.
In simple words: Lead and mercury are poor heat conductors.

Exam Tip: Lead and mercury are exceptions to the general rule that metals are good conductors of heat and electricity.

Question 7. Name a non-metal which is in liquid state and a metal which is found in liquid state.
Answer: Bromine is a non-metal that exists in a liquid state. Mercury is a metal that is also found in a liquid state.
In simple words: Bromine is a liquid non-metal, and mercury is a liquid metal.

Exam Tip: These are important examples as they are the only common elements that are liquid at room temperature in their respective categories.

Question 8. Non-metals are non-lustrous, except one. Name the non-metal that is lustrous.
Answer: Iodine is a non-metal that has a shiny appearance.
In simple words: Iodine is the only non-metal that looks shiny.

Exam Tip: Iodine's lustrous property is an important exception to the general characteristics of non-metals.

Question 9. What are such metals called, which are soft, can be cut with knife, low densities and low melting point?
Answer: Such metals, which are soft, can be sliced with a knife, and possess low densities and low melting points, are known as alkali metals. Examples include sodium and potassium.
In simple words: Metals that are soft, knife-cuttable, and have low density and melting points are called alkali metals, like sodium and potassium.

Exam Tip: Remember these characteristic properties of alkali metals, which explain their high reactivity.

Question 10. Name two metals with very low melting point.
Answer: Gallium and caesium are two metals that have very low melting points.
In simple words: Gallium and caesium melt at very low temperatures.

Exam Tip: These metals can even melt in your hand due to their exceptionally low melting points.

Question 11. Name two allotropes of carbon.
Answer: Diamond and graphite are two different forms of carbon.
In simple words: Diamond and graphite are two forms of carbon.

Exam Tip: Allotropes are different structural forms of the same element, showing varying physical properties but identical chemical behavior.

Question 12. Name two metal oxides which are soluble in water.
Answer: Sodium oxide and potassium oxide are two metal oxides that can dissolve in water.
In simple words: Sodium oxide and potassium oxide can dissolve in water.

Exam Tip: These are basic oxides that react with water to form strong alkalis.

Question 13. Name two metals which are stored by keeping them immersed in kerosene.
Answer: Sodium and potassium are two metals that are kept submerged in kerosene.
In simple words: Sodium and potassium are stored in kerosene.

Exam Tip: This storage method is crucial due to their high reactivity with air and moisture.

Question 14. Why is sodium/potassium kept immersed in kerosene oil?
Answer: Sodium and potassium are extremely reactive metals; they can catch fire if left exposed to air. Therefore, they are kept submerged in kerosene oil to prevent this reaction.
In simple words: Sodium and potassium are very reactive and burn in air, so they are stored in kerosene oil.

Exam Tip: This prevents them from reacting with atmospheric oxygen and moisture, which would lead to rapid oxidation and combustion.

Question 15. Why is it that sodium when react with water form sodium hydroxide whereas aluminium forms only aluminium oxide?
Answer: Sodium metal reacts with water, creating sodium oxide, which then dissolves in water to form sodium hydroxide. In contrast, aluminium oxide does not dissolve in water, so it only forms aluminium oxide, not aluminium hydroxide.
In simple words: Sodium makes sodium hydroxide because its oxide dissolves in water, but aluminium only makes aluminium oxide because its oxide does not dissolve.

Exam Tip: The solubility of the metal oxide in water determines whether the hydroxide or just the oxide is the final product.

Question 16. Magnesium when reacts with hot water starts floating. Explain.
Answer: When magnesium reacts with hot water, it creates magnesium oxide and releases hydrogen gas. This hydrogen gas causes the magnesium to float. Small bubbles of hydrogen gas attach to the magnesium surface, and as the gas rises, it also lifts the magnesium.
In simple words: Magnesium floats in hot water because the hydrogen gas produced sticks to its surface, making it buoyant.

Exam Tip: The buoyancy is caused by the hydrogen gas bubbles sticking to the metal surface, which reduces its effective density.

Question 17. What are ionic bonds?
Answer: Ionic bonds are connections created between a metal and a non-metal through the transfer of electrons.
Example: \( Na^+ + Cl^- \implies NaCl \)
In simple words: Ionic bonds form when a metal gives electrons to a non-metal, like in table salt.

Exam Tip: Emphasize the complete transfer of electrons, leading to the formation of oppositely charged ions that attract each other.

Question 18. Name two metals which are ductile and malleable.
Answer: Gold and silver are two metals that can be stretched into thin wires (ductile) and hammered into thin sheets (malleable).
In simple words: Gold and silver are metals that are both ductile and malleable.

Exam Tip: These properties allow metals to be shaped without breaking, making them useful for jewelry and coinage.

Question 19. Which ores are converted into metal oxides by calcination?
Answer: Carbonate ores are the types of ores that get changed into metal oxides through the process of calcination.
In simple words: Carbonate ores become metal oxides through calcination.

Exam Tip: Calcination specifically applies to carbonate ores and involves heating in the absence of air, releasing carbon dioxide.

Question 20. Name the ores of mercury.
Answer: The ores of mercury are called cinnabar, which has the chemical formula \( HgS \).
In simple words: Cinnabar is the ore from which mercury is obtained.

Exam Tip: Remember common ore names and their corresponding metals, especially for frequently tested examples like cinnabar.

Question 21. Name three common types of ores where metal exists in nature.
Answer: Oxide ores, carbonate ores, and sulphide ores are three common kinds of ores where metal naturally occurs.
In simple words: Metals are found naturally in oxide, carbonate, and sulphide ores.

Exam Tip: These classifications are based on the primary chemical form in which the metal is found in the Earth's crust.

Question 22. What is gangue?
Answer: Gangue refers to the unwanted impurities found in an ore, such as soil, sand, and other rocky material.
In simple words: Gangue is the useless dirt and rock mixed with valuable ore.

Exam Tip: Distinguish gangue from the valuable mineral within an ore; gangue is removed during the concentration process.

Question 23. What is concentration of ore?
Answer: Concentration of ore is the process where unwanted impurities are taken out from the ore.
In simple words: Concentration of ore means removing impurities from it.

Exam Tip: This is the initial step in metallurgy, aimed at increasing the proportion of the desired metal in the ore.

Question 24. What are two types of reducing agents used to reduce metal oxide to metal?
Answer: Carbon and very reactive metals, like sodium, calcium, and aluminium, are two kinds of reducing agents often used to turn metal oxides into pure metal.
In simple words: Carbon and very reactive metals like sodium are used to reduce metal oxides.

Exam Tip: The choice of reducing agent depends on the reactivity of the metal; more reactive metals require stronger reducing agents or electrolytic reduction.

Question 25. During electrolytic refining of a metal, what type of electrolyte should one take?
Answer: When performing electrolytic refining of impure metals, the electrolyte chosen should be a solution of the same impure metal.
In simple words: For refining, the electrolyte must be a solution of the impure metal itself.

Exam Tip: The electrolyte must contain ions of the metal being refined to allow for deposition onto the cathode.

Question 26. What is anode mud?
Answer: Anode mud refers to the impurities that gather at the bottom of the anode during the electrolytic refining process of metals.
In simple words: Anode mud is the collection of impurities that fall below the anode during metal refining.

Exam Tip: This mud often contains valuable noble metals like silver, gold, and platinum.

Question 27. What is rust?
Answer: Rust is the reddish-brown, flaky material that forms on iron when it is exposed to both air and moisture.
In simple words: Rust is the red-brown flaky layer that forms on iron when exposed to air and water.

Exam Tip: Remember that rust is specifically hydrated iron (III) oxide and requires both oxygen and water to form.

Question 28. Give one use of anhydrous calcium chloride.
Answer: Anhydrous calcium chloride is used as a drying agent because it absorbs moisture from the surrounding air.
In simple words: Anhydrous calcium chloride is used to dry things by absorbing moisture from the air.

Exam Tip: Its hygroscopic nature makes it effective in desiccators or as a desiccant in various applications.

Question 29. What makes silver turn black and copper turn green when kept exposed for few days?
Answer: When silver is left exposed to air, it becomes black because a layer of silver sulphide forms on its surface. Copper, when exposed for a few days, turns green due to the formation of a copper carbonate coating.
In simple words: Silver turns black from silver sulphide, and copper turns green from copper carbonate, both when exposed to air.

Exam Tip: These color changes are examples of corrosion, where metals react with substances in the atmosphere.

Question 30. What is amalgam?
Answer: An amalgam is an alloy formed when one of the metals in the mixture is mercury.
Example: \( Ag + Hg \implies \) silver amalgam.
In simple words: An amalgam is a metal mixture where one part is mercury.

Exam Tip: Amalgams are widely used in dentistry for tooth fillings due to their malleability and setting properties.

Question 31. What is solder?
Answer: Solder is an alloy that consists of a mixture of lead and tin.
In simple words: Solder is a metal mix of lead and tin.

Exam Tip: Solder is used for joining metals together, particularly in electronics, due to its low melting point.

Question 32. Name two alloys of copper.
Answer: Brass (a mix of copper and zinc) and bronze (a mix of copper and tin) are two alloys that contain copper.
In simple words: Brass and bronze are two alloys made with copper.

Exam Tip: Knowing the composition of common alloys is important for understanding their properties and uses.

Question 33. Name two alloys of iron.
Answer: Two alloys of iron are steel, which is iron combined with carbon, and stainless steel, which is iron mixed with chromium, nickel, and carbon.
In simple words: Steel and stainless steel are two alloys that contain iron.

Exam Tip: These alloys are engineered to improve specific properties of iron, such as strength (steel) and corrosion resistance (stainless steel).

Question 34. Name two heavy metals.
Answer: Lead and Chromium are two examples of heavy metals.
In simple words: Lead and chromium are two heavy metals.

Exam Tip: Heavy metals are generally defined by their high density and are often associated with environmental concerns.

Question 35. Name two sources of heavy metal pollution.
Answer: Two origins of heavy metal pollution include discarded mercury thermometers and lead-acid batteries or battery cells disposed of in the garbage.
In simple words: Old mercury thermometers and thrown-out lead batteries are sources of heavy metal pollution.

Exam Tip: Proper disposal of products containing heavy metals is crucial to prevent environmental contamination and health risks.

Question 36. Name the solution used to dissolve gold in it.
Answer: Aqua regia is the specific solution that is used to dissolve gold.
In simple words: Aqua regia is the liquid used to dissolve gold.

Exam Tip: Remember that gold is a noble metal and does not react with common acids; aqua regia is unique in its ability to dissolve it.

Question 37. What is aqua-regia?
Answer: Aqua-regia is a newly made mixture consisting of one part concentrated nitric acid and three parts concentrated hydrochloric acid. This strong mixture has the ability to dissolve all metals.
In simple words: Aqua regia is a fresh blend of one part strong nitric acid and three parts strong hydrochloric acid, which can dissolve any metal.

Exam Tip: The precise 1:3 ratio of nitric acid to hydrochloric acid is essential for its unique dissolving properties.

Short Answer Type Questions

Question 1. Give electron dot structure of chlorine and oxygen.
Answer: Here are the electron dot structures for chlorine and oxygen:
(i) **Chlorine:** Atom `\( (\text{Valence electrons: 7}) \)`
Ion: `\( \text{Cl}^- (\text{Valence electrons: 8}) \)`
(ii) **Oxygen:** Atom `\( (\text{Valence electrons: 6}) \)`
Ion: `\( \text{O}^{2-} (\text{Valence electrons: 8}) \)`
These represent the electron configurations.
In simple words: For chlorine, the atom has 7 outer electrons and the ion has 8. For oxygen, the atom has 6 outer electrons and the ion has 8.

Exam Tip: Electron dot structures typically show valence electrons. Remember that atoms gain or lose electrons to achieve a stable octet (8 valence electrons) or duplet (2 for hydrogen/helium).

Question 2. Explain why the surface of some metals acquire dull appearance when exposed to air for long time?
Answer: Metals interact with various gases found in the air, creating new compounds. This causes their surfaces to lose their shine and appear dull when they are left exposed to air for an extended period. For instance, silver develops a black surface due to the formation of silver sulphide.
In simple words: Metals look dull after a while in air because they react with gases to form new compounds on their surface, like silver turning black due to silver sulphide.

Exam Tip: This process is known as corrosion or tarnishing, where a thin layer of oxide, sulphide, or carbonate forms on the metal surface.

Question 3. What are amphoteric oxides? Give two examples of amphoteric oxides.
Answer: Amphoteric oxides are oxides that can behave as both acids and bases. They will react with acids and bases alike to create salts. For example, aluminium oxide (\( Al_2O_3 \)) and zinc oxide (\( ZnO \)) are amphoteric oxides.
Example reactions:
\( Al_2O_3 + 6HCl \implies 2AlCl_3 + 3H_2O \)
\( Al_2O_3 + 2NaOH \implies 2NaAlO_2 + H_2O \)
In simple words: Amphoteric oxides act like both acids and bases, reacting with both to form salts; aluminium oxide and zinc oxide are examples.

Exam Tip: Remember that amphoteric oxides are exceptions to the general rule of metal oxides being basic and non-metal oxides being acidic.

Question 4. Define alloy. Give two advantages of making alloys.
Answer: An alloy is a uniform blend of two or more metals, or a metal with one or more non-metals. Two benefits of making alloys are to improve the characteristics of metals, for instance, making them tougher or more resistant to rust, and to change qualities like reducing the melting point, as is done for solder.
In simple words: Alloys are mixtures of metals (or metal and non-metal) made to improve properties like strength, rust resistance, or to lower melting points.

Exam Tip: Focus on alloys as a method to tailor the properties of metals for specific applications beyond what pure metals can offer.

Question 5. Why do ionic compounds conduct electricity?
Answer: Ionic compounds can conduct electricity when they are in a molten (melted) state or dissolved in water. This happens because they break apart into separate positive and negative ions, which are then free to move and carry the electric current.
In simple words: Ionic compounds conduct electricity when melted or dissolved because their ions become free to move.

Exam Tip: The key is the mobility of ions; in solid ionic compounds, ions are fixed and cannot conduct electricity.

Question 6. Why do covalent compounds have low melting point?
Answer: Covalent compounds are composed of covalent bonds. These bonds are not very strong, so they require less heat energy to break, resulting in a low melting point.
In simple words: Covalent compounds have low melting points because their bonds are not strong and need little heat to break.

Exam Tip: Compare this to ionic compounds, which have strong electrostatic attractions requiring much more energy to overcome.

Question 7. Why jewellery made of 24 carat gold is not preferred?
Answer: Jewellery made from 24-carat gold is not preferred because pure gold is extremely ductile and malleable. This means that ornaments made from it would not keep their shape for an extended period. Therefore, an alloy of gold and copper is commonly used to create jewellery that maintains its form and design.
In simple words: Pure 24-carat gold is too soft for jewelry, so it's mixed with copper to make it harder and help it keep its shape.

Exam Tip: The purity of gold affects its hardness; alloying with other metals like copper increases its durability for practical use.

Question 8. State five points of differences between ionic compound and covalent compound.
Answer: Here are five key differences between ionic and covalent compounds:
**Ionic Compound:**
- Ionic compounds have ionic bonds that consist of ions.
- Electrons are lost and gained.
- They can carry electricity (in molten or solution state).
- They possess a high melting point.
- They dissolve in water (often).
**Covalent Compound:**
- Covalent compounds are made of covalent bonds, involving atoms rather than ions.
- Electrons are shared between atoms.
- Covalent compounds generally do not conduct electricity.
- They have a low melting point.
- They do not dissolve in water (often).
In simple words: Ionic compounds involve electron transfer, form ions, conduct electricity when melted, and have high melting points, while covalent compounds involve electron sharing, form molecules, don't conduct electricity, and have low melting points.

Exam Tip: Focus on the fundamental difference in bonding (transfer vs. sharing of electrons) as it explains most of their contrasting physical and chemical properties.

Question 9. What is thermite reaction? Give its one use.
Answer: A thermite reaction is a process where a more reactive metal acts as a reducing agent, converting a metal oxide into its pure metal. This reaction generates a large amount of heat, making it highly exothermic. The metal formed in these reactions is in a molten state and is used for joining railway tracks or repairing cracked machine parts.
Example:
\( Fe_2O_3(s) + 2Al(s) \implies 2Fe(l) + Al_2O_3(s) + \text{heat} \) (molten state)
In simple words: A thermite reaction is a very hot chemical process where a reactive metal removes oxygen from a metal oxide, producing molten metal used for welding railway tracks.

Exam Tip: The key features of a thermite reaction are its strong exothermic nature and the production of metal in a molten state, which is vital for its welding applications.

Question 10. How can you obtain pure metal from ores of metals of high reactivity?
Answer: To get pure metal from ores of highly reactive metals, several steps are followed:
1. **Concentration of ore:** This involves removing impurities from the ore.
2. **Electrolysis of molten ore:** The concentrated ore is then melted and subjected to electrolysis. During this process, the pure metal is collected at the cathode of the electrolytic cell.
Examples of such metals include sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca).
In simple words: Highly reactive metals are purified from their ores by first concentrating the ore to remove impurities, then melting it and using electricity (electrolysis) to extract the pure metal at the cathode.

Exam Tip: Electrolytic reduction is necessary for highly reactive metals because they have very stable oxides that cannot be reduced by common reducing agents like carbon.

Question 11. Metals when react with nitric acid does not release hydrogen gas. Explain.
Answer: Nitric acid is a potent oxidizing agent. When metals typically react with other acids, they release hydrogen gas. However, with nitric acid, the hydrogen produced gets oxidized further, forming water instead. There are two notable exceptions: magnesium (Mg) and manganese (Mn) can release hydrogen gas when reacting with dilute nitric acid.
In simple words: Nitric acid is a strong oxidizer, so it turns the hydrogen gas released by metals into water, rather than allowing it to escape as gas, except for magnesium and manganese.

Exam Tip: The oxidizing nature of nitric acid is the primary reason for the absence of hydrogen gas; remember the exceptions (Mg and Mn) as they are frequently asked.

Question 12. Show the following reactions with balanced equations:
(a) Calcium + Water
(b) Aluminium + Water
Answer:
(a) The reaction of calcium with water produces calcium hydroxide and hydrogen gas.
\( Ca + 2H_2O \implies Ca(OH)_2 + H_2(g) \)
(b) Aluminium reacting with water creates aluminium oxide and hydrogen gas.
\( 2Al(s) + 3H_2O(g) \implies Al_2O_3(s) + 3H_2(g) \)
In simple words: Calcium and water make calcium hydroxide and hydrogen gas. Aluminium and water produce aluminium oxide and hydrogen gas.

Exam Tip: Ensure all equations are correctly balanced for both mass and charge, and state symbols (s, l, g, aq) are included where appropriate.

Question 13. Name the property of metal used in the following cases:
(a) Aluminium foil
(b) Metal jewellery.
(c) Cable wires
(d) Bells
Answer: Here are the metal properties utilized in each case:
(a) **Aluminium foil:** Malleability, which allows it to be flattened into thin sheets.
(b) **Metal jewellery:** Lustre (shininess), malleability (ability to be shaped), and ductility (ability to be drawn into wires).
(c) **Cable wires:** Good conductivity of electricity and ductility, enabling them to carry current and be drawn into long wires.
(d) **Bells:** Sonority, meaning they produce a ringing sound when struck.
In simple words: Aluminium foil uses malleability. Jewellery uses shine, malleability, and ductility. Cable wires use electrical conductivity and ductility. Bells use sonority for sound.

Exam Tip: Be ready to link specific physical properties of metals (like malleability, ductility, conductivity, sonority, lustre) to their practical applications.

Question 14. Why are metals good conductors of electricity?
Answer: Metals are excellent conductors of electricity because they possess free electrons. These electrons can move easily throughout the metal structure, allowing electric current to flow. Furthermore, metals provide very little resistance to this electron flow.
In simple words: Metals conduct electricity well because they have free-moving electrons that can carry electric current easily through them.

Exam Tip: The concept of a "sea of delocalized electrons" is key to understanding metallic bonding and conductivity.

Question 15. Why is aluminium extracted from alumina (Al2O3) by electrolytic reduction and not by reducing with carbon?
Answer: The bond connecting aluminium and oxygen is considerably stronger, making it difficult for carbon to remove oxygen from it. Consequently, carbon cannot serve as an effective reducing agent in this process. To extract aluminium from alumina (\( Al_2O_3 \)), electrolytic reduction is performed. This method uses electricity to separate aluminium and oxygen, with pure aluminium being collected at the cathode.
In simple words: Aluminium is extracted from alumina using electricity because the bond between aluminium and oxygen is too strong for carbon to break.

Exam Tip: This illustrates that for highly reactive metals (like aluminium), electrolytic reduction is necessary due to the stability of their oxides.

Question 16. Ionic salts do not conduct electricity in solid state but conducts electricity in molten state.
Answer: Ionic salts do not conduct electricity when in a solid state because their ions are held tightly in a fixed lattice and cannot move freely. However, when these ionic compounds are melted or dissolved in water, the ions become mobile and are then able to move, thereby conducting electricity.
In simple words: Solid ionic salts don't conduct electricity because their ions are stuck, but when melted or dissolved, the ions can move freely and conduct.

Exam Tip: The ability to conduct electricity in ionic compounds depends entirely on the mobility of their ions, which is achieved through melting or dissolution.

Question 17. The use of iron metal is causing lot of economical loss. Justify this statement.
Answer: Iron metal often leads to significant economic losses. When used in large-scale commercial applications such as building construction, railways, or bridges, iron is susceptible to rusting. Rusting weakens the metal, which can cause structures to break down and fail. Although iron is strong, inexpensive, and readily available, its tendency to rust results in considerable financial loss and damage.
In simple words: Iron causes financial loss because it rusts, weakening structures in buildings and railways, even though it's cheap and strong.

Exam Tip: Emphasize the economic impact of rusting, linking it directly to the structural integrity and maintenance costs of iron-based constructions.

Question 18. Give three points of difference between metals and non-metals based on physical properties.
Answer: Here are three key physical differences between metals and non-metals:
**Metals:**
- Most metals exist in a solid state, with the exception of mercury.
- Metals generally have a high melting point.
- Metals are typically ductile (can be drawn into wires) and malleable (can be hammered into sheets).
**Non-metals:**
- Non-metals can be found in solid, liquid, or gaseous states.
- Non-metals usually have a low melting point.
- Non-metals are generally non-ductile and non-malleable; they tend to be brittle.
In simple words: Metals are usually solid, shiny, and can be shaped, while non-metals can be solid, liquid, or gas, are not shiny, and are brittle.

Exam Tip: When differentiating, pick clear, distinct physical properties like state at room temperature, luster, malleability/ductility, and melting points.

Question 19. Give reasons:
1. Aluminium oxide is amphoteric oxide.
2. Non-metals do not conduct electricity.
3. Metals displace hydrogen gas from acids.
Answer: Here are the reasons for the given statements:
1. **Aluminium oxide is amphoteric:** It exhibits characteristics of both acidic and basic oxides, meaning it reacts with both acids and bases to create salt and water.
2. **Non-metals do not conduct electricity:** Non-metals lack free ions, which are necessary for the flow of electric current. As a result, they are unable to conduct electricity.
3. **Metals displace hydrogen gas from acids:** When metals react with acids, they donate electrons to the hydrogen ions present in the acid. These hydrogen ions then become hydrogen atoms, which subsequently combine to form hydrogen gas.
In simple words: Aluminium oxide acts as both acid and base. Non-metals don't conduct electricity due to lack of free ions. Metals displace hydrogen from acids by giving electrons to hydrogen ions.

Exam Tip: For "give reasons" questions, provide a clear, concise scientific explanation that directly answers why the statement is true.

Long Answer Type Questions

Question 1. Show that for rusting of iron both air and moisture are required.
Answer: To demonstrate that both air and moisture are necessary for iron to rust, an experiment can be set up using three test tubes (A, B, and C).
**Test tube A:** Contains two iron nails, water, and is sealed with a cork, exposing the nails to both air and water.
**Test tube B:** Contains two iron nails, boiled distilled water (to remove dissolved air), and 1 mL of oil on top to prevent air contact. It is also sealed with a cork.
**Test tube C:** Contains two iron nails and anhydrous calcium chloride (a drying agent) to absorb all moisture, and is sealed with a cork.
**Observation:** It is noticed that only the nails in test tube A undergo rusting. This confirms that the nails were directly exposed to both air and water. In test tube B, the oil layer stops the nails from contacting air, so no rust forms. In test tube C, the anhydrous calcium chloride prevents contact with both air and water, thus preventing rusting.
In simple words: An experiment with three test tubes shows that iron needs both air and water to rust. One test tube with both rusts, one with no air doesn't, and one with no water also doesn't.

Exam Tip: Clearly describe the setup of each test tube, the specific conditions (presence/absence of air and water), and the expected outcome for full marks.

Question 2. (a) Arrange the given metals in activity series: Fe, Au, Zn, Al, Cu. (b) State two points of difference between calcination and roasting with an example of each.
Answer:
(a) The arrangement of metals from most reactive to least reactive is known as the activity series of metals. For the given metals, the order of decreasing reactivity is:
\( Al > Zn > Fe > Cu > Au \)
(b) Here are two key differences between calcination and roasting, along with an example for each:

Exam Tip: For the activity series, remember the mnemonic 'Please Stop Calling Me A Zebra Instead Try Learning How Copper Saves Gold' (Potassium, Sodium, Calcium, Magnesium, Aluminium, Zinc, Iron, Lead, Hydrogen, Copper, Silver, Gold). For calcination and roasting, differentiate by the type of ore and the presence/absence of oxygen.

Question 3. (a) Explain why copper is used to make taps, hot water tanks and not any other metal? (b) What will happen if iron nails are kept in a solution containing copper sulphate? (c) Write the chemical equations for the following and balance it.
(i) Ca + H2O →
(ii) Al + HCl →
(iii) Fe + H2O →
Answer:
(a) Copper is favored for making taps and hot water tanks over other metals for several reasons. It does not react with any type of water, even steam. Additionally, it is inexpensive and widely available, making it a practical choice for these applications.
(b) If iron nails are placed in a copper sulphate solution, the solution's blue color will gradually fade. This occurs because iron displaces copper from the solution, leading to the deposition of reddish-brown copper metal near the surface of the iron nails.
(c) Here are the balanced chemical equations for the given reactions:
(i) **Calcium + Water:** Calcium reacts with water to produce calcium hydroxide and hydrogen gas.
\( Ca + 2H_2O \implies Ca(OH)_2 + H_2(g) \)
(ii) **Aluminium + Hydrochloric Acid:** Aluminium reacts with hydrochloric acid to form aluminium chloride and hydrogen gas.
\( 2Al + 6HCl \implies 2AlCl_3 + 3H_2(g) \)
(iii) **Iron + Steam:** Iron reacts with steam to yield iron oxide and hydrogen gas.
\( 3Fe + 4H_2O \implies Fe_3O_4 + 4H_2(g) \)
In simple words: (a) Copper is chosen for taps and tanks because it resists water, is cheap, and conducts heat well. (b) Iron nails in copper sulphate will make the solution fade from blue as iron replaces copper. (c) Reactions are shown with calcium and water, aluminium and hydrochloric acid, and iron and steam.

Exam Tip: For explanations, connect the properties (e.g., reactivity, availability) to the application. For displacement reactions, remember the activity series. For equations, ensure reactants and products are correct and the equation is balanced.

Question 4. What is meant by 'refining of metals'? Describe the electrolytic refining of copper with a neat labelled diagram.
Answer: Extracting unwanted substances from a metal and making it clean is known as refining of metals. The electrolytic refining of copper involves setting up the apparatus as shown in the accompanying picture. The anode is made of impure copper metal, while the cathode is a pure copper strip. The electrolyte used is acidified copper sulphate solution. When an electric current moves through the setup, impurities gather below the anode, forming what is called anode mud. Meanwhile, the pure metal accumulates at the cathode.
In simple words: Refining metals means making them pure by removing unwanted stuff. For copper, we use electricity to clean it. Impure copper goes to the anode, pure copper to the cathode, and impurities collect as "anode mud."

Exam Tip: Clearly define each part of the electrolytic cell (anode, cathode, electrolyte) and explain their roles to score full marks. A simple diagram, even mental, helps organize the explanation.

Question 5. How can you prove that zinc is more reactive than copper?
Answer: To prove that zinc is more reactive than copper, use pieces of zinc and copper, along with two test tubes holding copper sulphate and zinc sulphate solution. Place the zinc piece into the copper sulphate solution, and the copper metal into the zinc sulphate solution. What you will see: The test tube containing zinc in copper sulphate will display a reaction, visible as the blue color of the copper sulphate gradually disappears. The other test tube will remain unchanged. This demonstrates that zinc is more reactive than copper, meaning it can push copper out of its salt solution.
In simple words: To show zinc is more reactive, put zinc in copper sulphate and copper in zinc sulphate. The zinc will make the blue copper solution fade and deposit copper, proving it's more reactive.

Exam Tip: When proving reactivity, always choose a metal and a salt solution where a displacement reaction is expected if the metal is more reactive. Observe color changes and solid deposits.

Practical Based Questions (Solved)

Question 1. Three metals looks similar in the lab and they are zinc, magnesium and aluminium. A student wants to confirm the identity of each metal. How can he use the reactivity test to do so?
Answer: A student could use three test tubes, each filled with zinc sulphate, and then place a small piece of each unknown metal into them. The test tube showing no reaction likely contains the zinc metal itself. Next, to find the aluminium metal, the student should take two more test tubes and put aluminium sulphate into both. Then, add magnesium to one tube and aluminium to the other. The tube that shows no reaction indicates where the aluminium metal was added. The remaining metal must be magnesium.
In simple words: To tell zinc, magnesium, and aluminum apart, put each in zinc sulphate. The one that doesn't react is zinc. Then, take the other two and put them in aluminum sulphate. The one that doesn't react is aluminum, and the last one is magnesium.

Exam Tip: Use a step-by-step approach, testing reactivity against a known solution to identify the least reactive metal first, then moving to more reactive ones.

Question 2. The lab attendant made three solutions of zinc sulphate, magnesium sulphate and aluminium sulphate. He forgot to label the reagent bottles. Explain how you can label these bottles by using the metal reactivity studies.
Answer: Start with three test tubes, adding a small amount of each solution from the unlabelled bottles into separate tubes. Next, put a tiny piece of magnesium into each tube. The test tube where no change happens indicates that the solution is magnesium sulphate. For the remaining two solutions, transfer them into two new test tubes and then introduce a small piece of aluminium metal to each. The tube that shows no reaction contains aluminium sulphate, and the remaining solution is zinc sulphate.
In simple words: To label the solutions, first put magnesium into each unknown solution. The one that doesn't react is magnesium sulphate. Then, take the other two solutions, put aluminum into them. The one that doesn't react is aluminum sulphate, and the last one is zinc sulphate.

Exam Tip: Always start with a metal or solution that is less reactive to observe clear displacement reactions, making identification easier.

Question 3. A student kept a spatula in the test tube containing copper sulphate. Record his observation next day.
Answer: The student would notice a change in the solution's color, from blue to light green. Also, a reddish-brown coating of copper metal would appear on the iron spatula. This happens because iron is more reactive than copper, so it displaces copper from the copper sulphate solution.
In simple words: The blue copper solution will turn light green, and a reddish layer of copper will form on the spatula because iron pushes copper out of its solution.

Exam Tip: Remember that displacement reactions are common in reactivity series experiments, often resulting in color changes in the solution and deposits on the more reactive metal.

Question 4. Name any three metal salts which are white in colour.
Answer: Some metal salts that appear white are magnesium sulphate, aluminium sulphate, and zinc sulphate.
In simple words: Magnesium sulphate, aluminum sulphate, and zinc sulphate are examples of white metal salts.

Exam Tip: Many common metal salts are white or colorless. For this type of question, recalling basic metal compounds from experiments is helpful.

Question 5. How will you identify the copper sulphate, iron sulphate and barium sulphate salts in the lab?
Answer: Iron sulphate usually has a green color (when it's ferrous sulphate) and a brown color if it is ferric sulphate. Copper sulphate has a blue color, while barium sulphate is a white-colored salt. By observing these distinct colors, one can easily identify each salt in the laboratory.
In simple words: You can tell these salts apart by their colors: iron sulphate is green or brown, copper sulphate is blue, and barium sulphate is white.

Exam Tip: Learning the characteristic colors of common metal salts is an easy way to identify them in the lab without complex tests.

Question 6. State the safety precautions for handling metals like sodium or potassium in the lab.
Answer: Very reactive metals such as sodium and potassium require extremely cautious handling. Avoid touching them with bare hands. Never pour water carelessly on them, as this could cause a fire and explosion. Should any contact with sodium or potassium result in burning, immediately flush the affected skin area with plenty of water until the irritation goes away, and then seek medical help.
In simple words: Handle sodium and potassium very carefully; don't touch with bare hands or put water on them, as it can cause fire. If skin contact happens, wash immediately with water and get help.

Exam Tip: Always prioritize safety in the lab. For highly reactive substances, wear protective gear and understand emergency procedures before beginning any experiment.

Question 7. Give three safety measures one should take while performing the reactivity series experiment in the lab.
Answer: When performing reactivity series experiments in the lab, it's important to follow these safety measures:
1. Prevent metals or any chemicals from touching your skin.
2. Do not breathe in any fumes or gases released during the experiment.
3. Avoid tasting any chemicals or materials, and always use clean apparatus that is free from contamination.
4. Wear safety goggles, hand gloves, and a lab coat before handling any chemicals.
In simple words: In reactivity experiments, make sure chemicals don't touch your skin, avoid breathing fumes, never taste anything, use clean tools, and always wear safety goggles, gloves, and a lab coat.

Exam Tip: Following general lab safety rules and specific precautions for the chemicals being used is crucial to prevent accidents during experiments.