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

Metals and Non-Metals Textbook Questions Solved

 

Question 1.1. Which metal is found in liquid state at room temperatures:
(a) sodium
(b) magnesium
(c) mercury
(d) aluminium
Answer: (c) mercury
In simple words: Mercury is the only metal that is naturally a liquid at normal room temperature. All other common metals like sodium, magnesium, and aluminium are solids.

🎯 Exam Tip: Remember this unique property of mercury as it's a common distinguishing feature from other metals.

 

Question 1.2. The non-metal which is conductor of electricity
(a) coal
(b) graphite
(c) sulphur
(d) nitrogen
Answer: (b) graphite
In simple words: Graphite is special because it's a non-metal that can carry electricity, unlike most non-metals. It has free electrons that help in conduction.

🎯 Exam Tip: Always remember graphite as the exception to the rule that non-metals are poor conductors of electricity.

 

Question 1.3. Which is most reactive from the following metals:
(a) gold
(b) sodium
(c) magnesium
(d) silver
Answer: (b) sodium
In simple words: Sodium is very quick to react with other substances, especially air and water, making it much more reactive than gold, magnesium, or silver. This is why it is usually stored in kerosene.

🎯 Exam Tip: Familiarize yourself with the reactivity series of metals to easily identify the most and least reactive elements.

 

Question 1.4. Metals form on reacting with oxygen-
(a) acidic oxides
(b) basic oxides
(c) neutral oxides
(d) non-reactive oxides
Answer: (b) basic oxides
In simple words: When metals combine with oxygen, they usually create compounds called basic oxides, which can turn red litmus paper blue. This is a common chemical property of metals.

🎯 Exam Tip: Understand the difference in oxide nature (acidic, basic, neutral) for metals and non-metals as it's a key chemical property.

 

Question 2. Fill in the blanks:
Answer:
1. 24
2. hydrogen
3. good conductor
4. acidic
In simple words: These are the words that fit into the blank spaces in the original questions. Each word completes a sentence related to metals and non-metals.

🎯 Exam Tip: For fill-in-the-blanks, always choose the most accurate and specific term to complete the statement correctly.

 

Question 3. Match the column 1 with column 2

Answer:
In simple words: This table shows the correct pairings between substances in Column 1 and their common uses in Column 2. Gold is used for jewellery, sulphur has medicinal uses, mercury is in thermometers, and graphite is found in pencils.

🎯 Exam Tip: Pay close attention to specific uses and properties of different elements to match them correctly in such questions.

 

Question 2. What are mixed metals?
Answer: Mixed metals are also known as alloys. They are formed when a small amount of a metal or non-metal is combined with a main metal. This mixing is done to achieve desired properties. For example, chromium and nickel are added to iron to make stainless steel, which protects it from rusting. In brass, zinc and copper are mixed together in specific amounts to create an alloy with improved properties.
In simple words: Mixed metals, or alloys, are made by combining a main metal with other metals or non-metals to get new, better materials. This helps improve things like strength or rust resistance.

🎯 Exam Tip: When defining alloys, mention that they are mixtures of a metal with other elements (metals or non-metals) and emphasize the purpose of mixing, which is to enhance properties.

 

Question 3. What is melting point of a substance?
Answer: The melting point of a substance is the specific temperature at which it changes from a solid state to a liquid state. Solids typically have high melting points because their particles are tightly packed and hard to separate. For example, iron (Fe) melts at a very high temperature, \( 1593^\circ C \). However, some exceptions exist, like gallium, which melts easily even when just held in your hand, showing it has a very low melting point.
In simple words: Melting point is the temperature where a solid turns into a liquid. Hard solids usually need a lot of heat to melt, but some special ones melt very easily.

🎯 Exam Tip: Clearly state the definition and provide examples of substances with both high and low melting points to illustrate the concept fully.

 

Question 4. Why is graphite a good conductor of electricity?
Answer: Graphite is an excellent conductor of electricity because of its unique structure. In graphite, each carbon atom links with three other carbon atoms on the same flat surface, forming hexagonal rings. One electron from each carbon atom is left free and can move around easily. These free electrons allow graphite to conduct electricity, making it useful in things like dry cells and electric arcs.
In simple words: Graphite conducts electricity well because its carbon atoms are arranged in layers, and each atom has one free electron that can move around to carry electric current.

🎯 Exam Tip: To explain graphite's conductivity, always mention its layered hexagonal structure and the presence of delocalized (free) electrons.

 

Question 5. Why lemon juice is not kept in iron containers?
Answer: Lemon juice is acidic because it contains citric acid. When this acidic juice is stored in iron containers, it reacts with the iron. This chemical reaction can produce harmful substances, making the food unsafe to eat and releasing hydrogen gas. This is why it's best to avoid keeping lemon juice in iron vessels.
In simple words: Lemon juice is acidic and reacts with iron containers, which can create harmful substances and release gas. So, it should not be stored in them.

🎯 Exam Tip: Emphasize the acidic nature of lemon juice and the reactivity of acids with metals as the core reason for not storing them in iron containers.

Metals and Non-Metals Long Answer Type Questions

 

Question 1. Why sodium metal is kept in kerosene?
Answer: Sodium metal is extremely reactive. It reacts quickly and violently with both oxygen in the air and water, often catching fire. To prevent this dangerous reaction and keep it safe, sodium is stored immersed in kerosene. Kerosene does not react with sodium, providing a protective layer that keeps it away from air and moisture.
In simple words: Sodium is very reactive and can burn in air or water. Keeping it in kerosene stops it from reacting with air and moisture, making it safe.

🎯 Exam Tip: Highlight sodium's high reactivity with air and water, and kerosene's inertness, as the main reasons for its storage method.

 

Question 2. Differentiate between metals and non-metals on the basis of their physical properties.
Answer: The physical properties of metals and non-metals show clear differences:

Physical properties of metals:
(a) State: Most metals are solid at normal room temperature, except for mercury (Hg), which is a liquid. This unique characteristic makes mercury useful in thermometers.
(b) Colour: Metals typically appear greyish in colour.
(c) Lustre: Metals are shiny and lustrous, meaning they can reflect light from their surface. Examples include gold, silver, copper, and aluminium.
(d) Hardness: Most metals are hard, but their hardness varies. Sodium and potassium, for instance, are soft and can be cut with a knife.
(e) Sonorous: Metals produce a ringing sound when struck with another hard object. This property, called sonority, is why metals are used to make bells and musical instruments.
(f) Density: Generally, metals have high density, meaning they are heavy and sink in water. However, some metals like sodium and potassium have lower densities and can float.
(g) Melting Point: Metals usually have high melting points due to their strong atomic bonds. For example, iron melts at \( 1593^\circ C \). Gallium is an exception, melting at a very low temperature, even in the palm of your hand.
(h) Heat conductivity: Metals are excellent conductors of heat. Silver (Ag) is the best, while lead (Pb) is the poorest conductor. This property is why cooking utensils are made of metals.
1. Malleability: Metals can be hammered into thin sheets without breaking. This property is known as malleability.
2. Ductility: Metals can be drawn or stretched into thin wires. This property is called ductility.
(k) Electricity conductivity: Metals allow electricity to flow through them easily. Silver is the best conductor of electricity. This ability to conduct heat and electricity, along with being hard, lustrous, sonorous, ductile, and malleable, defines metals.

Physical Properties of Non-Metals:
3. Lustre: Non-metals are generally dull and do not reflect light. Diamond and iodine are exceptions, as they are lustrous.
4. Hardness: Non-metals are usually soft. Diamond, which is the hardest known non-metal, is a notable exception.
5. Sonorous: Non-metals do not produce a ringing sound when struck; they are not sonorous.
6. Density: Non-metals generally have low density compared to metals.
7. Melting point: Non-metals typically have low melting points. Diamond and graphite, which are forms of carbon, are exceptions, having very high melting points.
8. Heat and electric conductivity: Non-metals are poor conductors of heat and electricity. Graphite is the only significant exception, being a good conductor.
9. Brittle: When hit with a hammer, non-metals usually break into powder or pieces; they are brittle.
In simple words: Metals are usually shiny, hard, can be shaped, make sounds, and conduct heat and electricity well. Non-metals are often dull, soft, break easily, don't make sounds, and are poor conductors, with a few special exceptions like graphite.

🎯 Exam Tip: Organize your answer with clear headings for metals and non-metals. For each property, provide contrasting examples and mention exceptions to score full marks.

 

Question 3. Write any four uses of metals.
Answer: Metals are widely used due to their unique properties:
1. Metals are used to make cooking utensils because they are good conductors of heat.
2. They are used in electric appliances, wires, and refrigerators, benefiting from their excellent electrical conductivity.
3. Metals such as iron and steel are essential for building structures like houses and bridges.
4. Precious metals like gold and silver are used in manufacturing jewellery and coins, and copper and aluminium are used for various other items.
In simple words: Metals are used for cooking pots, electrical wires, building homes, and making jewelry due to their heat conduction, electrical flow, strength, and beauty.

🎯 Exam Tip: When listing uses, briefly explain the property of the metal that makes it suitable for that particular application (e.g., good conductor of heat for cooking utensils).

 

Question 4. Why copper wire is use for wiring at our houses? Explain.
Answer: Copper wire is preferred for house wiring because copper is an excellent conductor of electricity. Electricity can flow through it very easily and efficiently. Copper ensures that electric current is carried uniformly and reliably throughout all the circuits in a house, which makes it a safe and effective choice for electrical wiring.
In simple words: Copper is used for house wiring because it carries electricity very well and evenly through all the connections.

🎯 Exam Tip: Emphasize copper's high electrical conductivity and uniform distribution of current as the key reasons for its use in household wiring.

 

Question 5. Write differences in metals and non metals on the basis of their chemical properties?
Answer: The chemical properties of metals and non-metals show distinct differences:

Chemical properties of metals:
Metals react with air, water, and acids to form various chemical substances.
(a) Reaction with air (Oxygen): Metals combine with oxygen in the air to form metal oxides.
\( \text{Metals} + \text{Oxygen} \rightarrow \text{Metal oxides} \)
For example, when a magnesium (Mg) ribbon burns, it turns into white ash (magnesium oxide). This ash, when dissolved in water, forms a basic solution.
(b) Reaction with water: Very reactive metals like sodium (Na) react vigorously with water, forming sodium hydroxide and hydrogen gas. Sodium is kept in kerosene because it reacts violently if exposed to water or air.
(c) Reaction with acid: Metals react with acids to produce hydrogen gas, which can be observed as bubbles.

Chemical properties of non-metals:
(a) Reaction with air (Oxygen): Non-metals also form oxides when they react with oxygen in the air. These non-metal oxides are typically acidic. For instance, burning sulphur powder produces sulphur dioxide \( (SO_2) \).
\( \text{Sulphur (S)} + \text{Oxygen (O}_2) \rightarrow \text{Sulphur dioxide (SO}_2) \)
When sulphur dioxide is dissolved in water, it forms sulphurous acid, which turns blue litmus paper red, proving its acidic nature.
(b) Reaction with water: Generally, non-metals do not react with water or steam. Phosphorus, being highly reactive, is kept in water to prevent its contact with air.
(c) Reaction with acids: Most non-metals do not react with dilute acids. However, some non-metals like sulphur can react with concentrated nitric acid to produce sulphur dioxide, nitrogen oxide, and water.
In simple words: Metals often react with air, water, and acids to form basic oxides and release hydrogen. Non-metals usually form acidic oxides with air, mostly don't react with water, and don't react with dilute acids.

🎯 Exam Tip: For chemical differences, clearly state the type of reaction (e.g., with air, water, acid) for both metals and non-metals, providing balanced chemical equations or specific examples where possible.

Metals and Non-Metals Additional Questions Solved

I. Multiple Choice Questions

 

Question 1. The most abundant metal in the earth's crust is:
(a) Oxygen
(b) Calcium
(c) Aluminium
(d) Gold
Answer: (c) Aluminium
In simple words: Aluminium is the most common metal found in the Earth's outer layer, making up a large part of its rocks and soil.

🎯 Exam Tip: Remember that aluminium is the most abundant metal, while oxygen is the most abundant element overall in the Earth's crust.

 

Question 2. The gas that burns with pop sound is:
(a) Nitrogen
(b) Oxygen
(c) Hydrogen
(d) Carbon dioxide
Answer: (c) Hydrogen
In simple words: Hydrogen gas makes a small "pop" sound when it burns. This is a common test to identify its presence.

🎯 Exam Tip: The "pop" sound test is characteristic for identifying hydrogen gas, a key observation in many chemical reactions.

 

Question 3. Which metals burn in air at high temperature with the evolution of much heat?
(a) Cu
(b) Hg
(c) Pb
(d) Al
Answer: (d) Al
In simple words: Aluminium burns in air at high temperatures, giving off a lot of heat. This shows its high reactivity under certain conditions.

🎯 Exam Tip: Focus on the reactivity of metals; more reactive metals tend to burn more readily and with more heat in air.

 

Question 4. Bronze is an alloy of
(a) Copper and Zinc
(b) Copper and Tin
(c) Zinc and Iron
(d) Copper and Gold
Answer: (b) Copper and Tin
In simple words: Bronze is a mixed metal made mainly from copper and tin. This combination creates a stronger and more durable material.

🎯 Exam Tip: Memorize the common compositions of important alloys like brass (copper and zinc) and bronze (copper and tin).

 

Question 5. Iron is galvanised by coating it with
(a) Chromium
(b) Sodium
(c) Magnesium
(d) Zinc
Answer: (d) Zinc
In simple words: Galvanisation is a process where iron is covered with a layer of zinc. This zinc coating protects the iron from rusting by acting as a sacrificial layer.

🎯 Exam Tip: Understand that galvanisation is a method of preventing rust, and zinc is the specific metal used for coating iron in this process.

 

Question 6. Metals react with oxygen to form their oxides which are generally
(a) Neutral in nature
(b) Basic in nature
(c) Acidic in nature
(d) None of these
Answer: (b) Basic in nature
In simple words: When metals react with oxygen, they typically form basic oxides. These oxides can react with acids and sometimes dissolve in water to form basic solutions.

🎯 Exam Tip: Differentiate between the nature of metal oxides (basic) and non-metal oxides (acidic) as this is a fundamental chemical property.

 

Question 7. A mineral from which a metal can be extracted on the commercial scale, economically is called
(a) Metal
(b) Metalloid
(c) Corrosion
(d) Ore
Answer: (d) Ore
In simple words: An ore is a special kind of rock or mineral from which we can get a metal easily and cheaply. It's like a rich source for a metal.

🎯 Exam Tip: Clearly distinguish between a 'mineral' (naturally occurring solid) and an 'ore' (a mineral from which metal can be profitably extracted).

 

Question 9. After the reaction of non-metals with water-
(a) Hydrogen gas formed
(b) Carbon dioxide gas is formed
(c) Non-metal oxides are formed
(d) Non-metals are unable to react with water
Answer: (d) Non-metals are unable to react with water
In simple words: Non-metals generally do not react with water, meaning they do not combine with it or change its composition.

🎯 Exam Tip: Remember this key chemical difference: metals react with water (some vigorously), while non-metals typically do not.

 

Question 10. Non-metal forms:
(a) Anion
(b) Cation
(c) Anion and Cation
(d) Do not form ion
Answer: (a) Anion
In simple words: Non-metals usually gain electrons to become negatively charged ions called anions. They do this to achieve a stable electron configuration.

🎯 Exam Tip: Understand the concept of ion formation: metals form cations by losing electrons, while non-metals form anions by gaining electrons.

 

Question 11. Metal which does not react even with steam:
(a) Potassium
(b) Iron
(c) Silver
(d) Magnesium
Answer: (c) Silver
In simple words: Silver is a less reactive metal and does not react with steam, unlike more reactive metals such as potassium or magnesium.

🎯 Exam Tip: The reactivity series helps predict how metals will react with water (cold, hot, or steam). Less reactive metals like silver show no reaction.

 

Question 12. Mercury is used in thermometer because:
(a) it does not wet the glass
(b) it is a liquid
(c) it expands on heating
(d) all of the options
Answer: (a) it does not wet the glass
In simple words: Mercury does not stick to the inside of the glass tube in a thermometer. This helps it move smoothly and give accurate temperature readings.

🎯 Exam Tip: For properties of thermometer liquids, remember that non-wetting of glass, uniform expansion, and a visible liquid state are all important.

 

Question 13. Substance conduct heat and electricity because of the property of:
(a) Ductivity
(b) Conductivity
(c) Malleability
(d) Sonority
Answer: (a) Ductivity
In simple words: Ductility is the ability of a material to be stretched into a thin wire without breaking. It describes the material's flexibility and strength.

🎯 Exam Tip: Be sure to clearly distinguish between ductility (can be drawn into wires) and conductivity (ability to pass heat or electricity).

 

Question 15. Which one of the following matter does not displace H2 gas from dilute HC1 or H2SO4?
(a) Mg
(b) Al
(c) Zn
(d) Cu
Answer: (d) Cu
In simple words: Copper cannot push hydrogen gas out of dilute acids like HCl or H2SO4 because copper is less reactive than hydrogen. This means it won't react with these acids to produce hydrogen gas.

🎯 Exam Tip: Metals below hydrogen in the reactivity series (like copper, silver, gold) do not react with dilute acids to produce hydrogen gas.

Metals and Non-Metals Very Short Answer Type Questions

 

Question 1. What is the nature of metal oxide?
Answer: Metal oxides are generally basic in nature. This means they can react with acids to form salt and water, and many of them will turn red litmus paper blue in solution. Some metal oxides, however, can also act as amphoteric, reacting with both acids and bases.
In simple words: Most metal oxides are basic, meaning they act like bases. They often react with acids and change red litmus to blue.

🎯 Exam Tip: Remember that metal oxides are typically basic, while non-metal oxides are typically acidic; note amphoteric oxides as exceptions.

 

Question 3. Define conductivity.
Answer: Conductivity is a property of materials that describes their ability to allow electricity or heat to pass through them. Metals are known for their high conductivity, which means they easily let electric current or heat flow. This property is due to the presence of free-moving electrons within their structure.
In simple words: Conductivity is how well something lets electricity or heat pass through it. Good conductors, like metals, allow current or heat to flow easily.

🎯 Exam Tip: When defining conductivity, specify that it applies to both heat and electricity, and mention the role of free electrons in metals.

 

Question 4. Why is aluminium used for making cooking coil?
Answer: Aluminium is used for making cooking coils because it is a lightweight metal that resists corrosion well. More importantly, it is a very good conductor of heat. Its efficient heat transfer properties ensure that food heats up quickly and evenly, making it an excellent material for cooking utensils.
In simple words: Aluminium is used for cooking coils because it's light, resists rust, and quickly spreads heat, making it good for cooking.

🎯 Exam Tip: Focus on aluminium's key properties: light weight, corrosion resistance, and especially good heat conductivity for its use in cooking.

 

Question 5. Which is more metallic, sodium or aluminium?
Answer: Sodium is more metallic than aluminium. Metallic character is related to a metal's tendency to lose electrons. Sodium is higher up in the activity series and has only one valence electron, which it readily loses. This makes it much more reactive and thus more metallic compared to aluminium, which has three valence electrons and a slightly different electron-losing tendency.
In simple words: Sodium is more metallic than aluminium because it loses electrons more easily. This makes it much more reactive.

🎯 Exam Tip: Remember that metallic character generally increases as you go down a group and decreases across a period in the periodic table, correlating with reactivity.

 

Question 6. What is the cause of rusting of iron?
Answer: Rusting of iron is caused by a process called oxide formation, specifically the formation of hydrated iron(III) oxide. This happens when iron reacts with oxygen in the presence of moisture (water). Both oxygen and water are necessary for iron to rust, and it's a slow chemical change that degrades the metal.
In simple words: Iron rusts when it reacts with oxygen and water, forming a reddish-brown iron oxide. Both air and moisture are needed for rust to form.

🎯 Exam Tip: State both oxygen and moisture as essential conditions for rusting and name the product as hydrated iron oxide.

Metals and Non-Metals Short Answer Type Questions

 

Question 1. What is galvanisation?
Answer: Galvanisation is a protective process used to prevent iron objects from rusting. It involves depositing a thin layer of zinc metal onto the surface of the iron. This zinc coating acts as a barrier, shielding the iron from contact with oxygen and moisture, and also provides electrochemical protection, making the iron less likely to corrode.
In simple words: Galvanisation is covering iron objects with a thin layer of zinc to stop them from rusting.

🎯 Exam Tip: When defining galvanisation, always mention the coating material (zinc) and its primary purpose (preventing rust/corrosion).

 

Question 2. Why does copper does not displace iron from iron sulphate solution?
Answer: Copper does not displace iron from an iron sulphate solution because copper is less reactive than iron. In the metal reactivity series, iron is placed above copper. A less reactive metal cannot displace a more reactive metal from its salt solution. Therefore, copper cannot replace iron in iron sulphate. This principle is fundamental to understanding single displacement reactions in chemistry.
In simple words: Copper cannot remove iron from iron sulphate because copper is not as reactive as iron. Only a more reactive metal can displace a less reactive one.

🎯 Exam Tip: To explain displacement reactions, always refer to the reactivity series of metals. A metal higher in the series can displace one lower in the series from its salt solution.

 

Question 4. Why do we store phosphorus in water?
Answer: Phosphorus is a highly reactive non-metal. It readily catches fire when exposed to air because it reacts vigorously with atmospheric oxygen. To prevent this spontaneous combustion, phosphorus is stored immersed in water. Water does not react with phosphorus, providing a safe medium that keeps the phosphorus isolated from oxygen and prevents it from catching fire.
In simple words: Phosphorus is kept in water because it reacts quickly and catches fire when it touches air. Water keeps it safe from oxygen.

🎯 Exam Tip: Highlight the high reactivity of phosphorus with air (oxygen) and its non-reactivity with water as the key reasons for its storage method.

 

Question 5. Write the equation of
1. copper with moist air
2. sodium with water
3. copper sulphate with zinc
4. magnesium with oxygen
Answer:
1. \( 2Cu + H_2O + CO_2 + O_2 \rightarrow Cu(OH)_2 + CuCO_3 \)
When copper reacts with moist air over time, it forms a green layer of basic copper carbonate.
2. \( 2Na + 2H_2O \rightarrow 2NaOH + H_2 \)
Sodium reacts vigorously with water to produce sodium hydroxide and hydrogen gas.
3. \( CuSO_4 + Zn \rightarrow Cu + ZnSO_4 \)
Zinc is more reactive than copper, so it displaces copper from copper sulphate solution, forming zinc sulphate and copper.
4. \( 2Mg + O_2 \rightarrow 2MgO \)
Magnesium burns in oxygen to form magnesium oxide, which is a white powder.
In simple words: These are the chemical recipes for different reactions. Copper forms a green layer in moist air. Sodium reacts with water to make hydrogen. Zinc takes copper's place in copper sulphate. Magnesium burns in oxygen to make magnesium oxide.

🎯 Exam Tip: Ensure that all chemical equations are balanced and correctly represent the reactants and products for each reaction.

Metals and Non-Metals Long Answer Type Questions

 

Question 1. Explain the uses of non metals.
Answer: Non-metals have many crucial uses across various fields:
1. Hydrogen and carbon are fundamental components of all living cells. Life as we know it would not be possible without these elements. Carbon, in the form of coal, is also a vital source for generating heat and energy.
4. Silicon is widely used in microchips and all types of electronic devices because of its semiconductor properties, which are essential for modern technology.
5. Phosphorus is an important ingredient in the match industry and is also used in agricultural fertilizers to support plant growth.
6. Sulphur has diverse applications, including in the manufacture of firecrackers, gunpowder, and sulphuric acid, a key industrial chemical.
7. Chlorine is an effective agent for disinfecting drinking water, helping to kill harmful bacteria and make water safe for consumption.
8. Iodine, when dissolved in alcohol to form tincture iodine, acts as an antiseptic and is used to treat wounds and cuts.
9. Helium is a lightweight, non-flammable gas primarily used to fill balloons for scientific, meteorological, and recreational purposes.
10. Argon is used in electric lights and advertisement signboards to create bright illumination. Similarly, neon is used in advertisement signboards and for creating distinctive lighting effects.
In simple words: Non-metals like carbon and hydrogen are basic for life. Silicon is in electronics, phosphorus in matches and fertilizers. Sulphur makes firecrackers, chlorine cleans water, iodine disinfects wounds, helium fills balloons, and argon/neon light up signs.

🎯 Exam Tip: When listing uses of non-metals, try to link each use to a specific property of the non-metal (e.g., chlorine for disinfection due to its oxidizing property).

 

Question 2. Show the reaction of sodium with water experimentally.
Answer: To observe the reaction of sodium with water, perform the following experiment:
First, take a beaker and fill it halfway with water. Next, carefully cut a small piece of sodium, roughly the size of a wheat grain. Gently press this sodium piece in a filter paper to remove any excess kerosene, then wrap it loosely in cotton. Carefully drop this cotton-wrapped sodium piece into the beaker of water. You will see a very strong and violent reaction, often with a flame. Wait until the reaction completely stops. After the reaction, touch the beaker to feel if it has become hot. Then, test the solution in the beaker using red and blue litmus paper. You will notice that the solution turns blue, indicating it is basic due to the formation of sodium hydroxide. This experiment shows that sodium reacts very violently with cold water, producing heat and a basic solution.
In simple words: When a small piece of sodium, wrapped in cotton, is put into water, it reacts strongly, gets hot, and forms a basic solution. This shows how reactive sodium is with water.

🎯 Exam Tip: For experiment descriptions, clearly list the materials, detailed steps, and the observable results. Mentioning safety precautions (like the small size of sodium and wrapping it) is also good practice.

 

Question 4. How do you observe conduction of electricity in metals?
Answer: To observe the conduction of electricity in metals, you can set up a simple circuit. Arrange the circuit with a battery, a switch, a bulb, and two free ends labeled A and B. Before testing, check if your circuit is working by touching ends A and B together; the bulb should glow. After this, attach different materials (like metallic wires, fibers, or threads) one at a time between ends A and B. Observe whether the bulb glows for each material. The observation will show that the bulb glows when metallic wires are attached, but not for non-metallic materials. This demonstrates that almost all metals are good conductors of electricity. The circuit allows us to visually confirm which materials permit the flow of electric current.
In simple words: To see if metals conduct electricity, make a simple circuit with a bulb. Connect different materials to the open ends. If the bulb lights up, that material, like a metal wire, conducts electricity.

🎯 Exam Tip: When describing an experiment for conductivity, always mention the components of the circuit (battery, switch, bulb) and the clear observation (bulb glowing/not glowing) to demonstrate conduction.

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