RBSE Class 8 Science Chapter 2 Metals and Non-Metals solutions is the best resource for students to revise all the important concepts of the chapter and score well in the exams. These textbook solutions will help the students to grasp a clear understanding of the different concepts and master it completely. We have covered all the questions and important topics of the RBSE Class 8 Science Solutions for Chapter 2 and made it easier for our learners.
Students can find chapter-wise explanations of important topics and questions of RBSE Class 8 Science that will help them to prepare for the RBSE Class 8 2020 exam in the most effective manner. Besides, it is advisable for students to implement a strategic learning process to score good marks in the examination. Here, we present you a collection of the Important Topics and Questions for all the chapters of RBSE Class 8 Science.
Meanwhile, here we have covered the important topics and questions with solutions for Chapter 2 from the RBSE Class 8 Science Syllabus. We hope by practising these questions, it will help the students to grasp a solid understanding of the chapter and revise it thoroughly before the exams. This will also enable the learners to build a strong foundation for the higher classes and also help them to get good grades in the exams.
Rajasthan Board Class 8 Science Chapter 2: BYJU’S Important Questions & Answers
RBSE Class 8 Science Chapter 2 Objective Questions: Textbook Important Questions and Solutions
Choose the correct options for the following:
Question 1: The metal which is found in liquid state at room temperatures —
Answer: c) Mercury
Question 2: The non metal which is a good conductor of electricity —
Answer: b) Graphite
Question 3: Which is most reactive from the following metals —
Answer: b) Sodium
Question 4: Metal form _______________ on reacting with oxygen.
- Acidic oxides
- Basic oxides
- Neutral oxides
Answer: a) Acidic oxides
Fill in the blanks:-
Question 5: Pure gold is ________________ carat.
Question 6: The reaction of metals with acid gives out _______________ gas.
Question 7: Metals are _____________ of heat and electricity.
Answer: good conductor
Question 8: The oxides of non metals are generally ___________ in properties.
Match Column A with Column B
|Column A||Column B|
|Q9. Gold||a. Medicinal use|
|Q10. Sulphur||b. Jewellery|
|Q11. Mercury||c. Pencil|
|Q12. Graphite||d. Thermometer|
|Column A||Column B|
|A9. Gold||a. Jewellery|
|A10. Sulphur||b. Medicinal use|
|A11. Mercury||c. Thermometer|
|A12. Graphite||d. Pencil|
RBSE Class 8 Science Chapter 2 Short Answer Type Questions: Textbook Important Questions and Solutions
Question 13: What is malleability?
Answer: When metals tend to spread or deform under pressure and are converted into sheets and wires either by hammering or rolling, this property is known as Malleability.
Question 14: What are mixed metals?
Answer: A combination of metals with one or more other elements are referred to as mixed metals, popularly known as an alloy. These mixed metals are designed for a specific purpose. Alloys are homogeneous solid mixtures of metals or a combination of metals and non-metals in small quantities.
For example, stainless steel is a mixture of chromium and nickel to prevent it from rusting. In brass, it is a combination of zinc and copper in varied proportions to achieve varying electrical and mechanical properties.
Question 15: What is the melting point of a substance?
Answer: The melting point of a substance is defined as the point of temperature at which a substance undergoes fusion from solid to liquid state. At melting point, the solid and liquid state tend to be in equilibrium. However, the melting point of a substance also depends on pressure. Metals have high melting points due to their hardness.
For example, metals like Iron (Fe) are hard in nature and have a high melting point of 1593° C. On the other hand, Gallium (Ga) has a very low melting point, which melts even when kept on the palm.
Question 16: Why is graphite a good conductor of electricity?
Answer: Graphite is a good conductor of electricity because of the presence of delocalised electrons. This means that each carbon atom forms only three covalent bonds with three other carbon atoms in the same structure, which gives it a hexagonal shape. Therefore, out of the four valence electrons in a carbon atom, only one of them is relatively free and such surfaces form weak bonds which are used in dry electric cells and is also considered a good lubricant.
Question 17: Why is lemon juice not kept in iron containers?
Answer: Lemon juice is acidic in nature. It contains citric acid which reacts when kept in iron containers. It forms poisonous substances and releases hydrogen in the process. For this reason, lemon juice should never be stored in an iron container.
RBSE Class 8 Science Chapter 2 Long Answer Type Questions: Textbook Important Questions and Solutions
Question 18: Why is sodium metal kept in kerosene?
Answer: Sodium is a highly reactive metal. It is kept in kerosene in order to prevent it from coming into contact with oxygen, carbon dioxide and moisture.
For example, if you take a piece of sodium (Na) on a filter paper and dip it in a beaker that’s filled with water. The sodium reacts with water and oxygen vigorously and produces sodium hydroxide (NaOH) and hydrogen (H2) gas which catches fire quickly. This may also cause a highly exothermic reaction.
To avoid direct reaction with air, sodium metal is kept in kerosene.
Question 19: Differentiate metals and non-metals on the basis of their physical properties.
Answer: Here we bring you the differences in the physical properties of metals and non-metals:
Physical properties of metals:
- Physical State: Most of the metals remain solid at room temperature except Mercury (Hg), which continues to be in liquid form even at room temperature.
- Colour: Metals are usually grey in colour.
- Lustre: Metals have special lustre which is referred to as a metallic shine. They tend to reflect light when a ray of light falls on them. Examples of lustrous metals include gold, silver, copper, aluminium, etc.
- Hardness: Most metals are generally hard. They cannot be cut or sliced easily. However, in comparison to other metals, sodium (Na) and potassium (K) can be easily cut like wood as they have a soft texture.
- Sonorous: When metals are struck with any hard or strong object, they tend to produce a special metallic sound, it is known as the sonorous nature of metals. Some of the examples of this property are used in bells, musical instruments, etc.
- Density: Most metals have high density. Heavy metals like steel spoon, iron nail, etc. have higher density because they are put in water, they tend to sink at the bottom of the container. On the other hand, metals such as sodium (Na) and potassium (K), which have low density tend to float on water.
- Melting point: The temperature at which any substance starts melting from solid to liquid state is known as melting point. Due to their hardness, metals usually have high melting points. For example, iron (Fe) has a high melting point of 1593° C. On the other hand, Gallium (Ga) has a very low melting point, which melts even when kept on the palm of a hand.
- Conduction of heat: Most metals are considered good conductors of heat. For example, when you heat a stainless steel spoon and a wooden block in a beaker filled with water, after sometime you’ll notice that the spoon becomes very hot whereas the wooden block does not. For this reason, kitchen utensils used for cooking are made up of iron, copper or aluminium so that they can heat up soon. Silver (Ab) is considered a good conductor of heat whereas lead (Pb) is not a good conductor of heat.
- Malleability: When metals spread on beating either by hammering or rolling and are converted into sheets and wires, this property is known as Malleability.
- Electrical conductivity: When metals allow electricity to pass through them, this property is known as electrical conductivity. Silver has the highest conductance of electricity.
- Ductility: When metals are drawn or stretched into thin wires, this property is known as ductility. All metals are generally ductile.
Hence, all those substances which are lustrous, hard, malleable, sonorous, ductile and good conductors of heat and electricity are known as metals.
Physical properties of non-metals:
- Physical State: Non-metals can either be in solid, liquid or gas state at room temperature. For example:
Solid – carbon (C), sulphur (S), iodine (I)
Liquid – bromine (Br)
Gas – oxygen (O2), nitrogen (N2), hydrogen (H2)
- Colour: Non-metals have different types of colours such as sulphur is yellow, chlorine gas is greenish yellow and phosphorus is pink in colour, etc.
- Lustre: Non-metals lack lustre as they do not reflect light. However, diamond and iodine are exceptions as they are lustrous in nature.
- Hardness: Non-metals are usually loose and soft in texture. Diamond is an exception as it is a form of carbon.
- Sonorous: Non-metals do not produce any sound when they strike against other objects.
- Density: Non-metals normally have very low density. For example, when you dip a piece of pencil or wooden stick in a glass beaker filled with water, you’ll notice that these items float on water. This is because they have lower density than water.
- Melting point: Non-metals are mostly known to have a very low melting point, except for graphite or diamond. Isotopes of carbon are said to have a very high melting point.
- Conductor of heat and electricity: Generally, non-metals are insulators, which implies that they are bad conductors of heat and electricity with graphite being an exception.
- Brittle: Non-metals cannot be drawn or stretched into sheets or wires by hammering due to its property of brittleness.
Question 20: Write any four uses of metals.
Answer: Here are four uses of metals:
- Metals are used for making cooking utensils.
- Metals such as iron or aluminium are used for building sheets and other materials.
- Metals are used in electric wires and appliances such as refrigerators, microwaves, etc.
- Metals are extensively used for making jewellery from gold, silver, etc.
Question 21: Why is copper wire used for wiring at our houses? Explain.
Answer: Copper is considered as a good conductor of electricity as electricity flows through it very easily. For this reason, copper is used in all circuits of electrical wiring at our houses.
Question 22: Write differences in metals and non-metals on the basis of their chemical properties.
Answer: Here we bring you the differences in the chemical properties of metals and non-metals:
Chemical properties of metals:
- Reaction of metals with air: Metals tend to form oxides on reacting with oxygen in the air. Metal + oxygen → Metal oxide. For example, when a thin ribbon of Magnesium is burned on a flame, it burns with light and white colour flames. Now, taking the ash if you mix with water in a test tube and test with litmus paper, it would turn into blue. Hence, the oxide formed from this reaction is acidic in nature, i.e., Magnesium (Mg) + Oxygen (O2) → Magnesium oxide (MgO). Similarly, aluminium and copper react with air to form oxides and tend to lose their lustre with regular use.
- Reaction of metals with water: Different types of metals react with water differently. For example, if sodium reacts with water, it forms sodium hydroxide or hydrogen gas. Sodium (Na) + Water (H2O) → Sodium hydroxide & Hydrogen gas (NaOH + H2). To avoid direct reaction with air and water, sodium metal is stored in kerosene. For example, take a piece of sodium (Na) on a filter paper and dip it in a beaker full of water. The sodium reacts with water and oxygen vigorously and produces sodium hydroxide (NaOH) and hydrogen (H2) gas which catches fire quickly.
- Reaction of metals with acid: Metals are said to react with acid and create hydrogen (H2) gas in the process.
Chemical properties of non-metals:
- Reaction of non-metals with air: Non-metals tend to react with air (oxygen) and form oxides which are acidic in nature. For example, take a small amount of powder sulphur in an inflammable spoon or metallic bottle and heat it. Once the sulphur starts burning, take it to a gas jar and cover it with a lid to avoid the gas from coming out. Slowly pour some water and cover it again. Thereafter, test it with a litmus paper, you’ll find the solution is acidic. Hence, the reaction of sulphur with oxygen forms sulphur dioxide gas which is acidic in nature, i.e., Sulphur (S) + Oxygen (O2) → Sulphur dioxide SO2.
- Reaction of non-metals with water: Non-metals normally do not react with either steam or water. As a result, Phosphorus is stored in water.
- Reaction of non-metals with acid: Most non-metals do not react with dilute acids. However, sulphur reacts with concentrated nitric acid (HNO3) and forms sulphur dioxide (SO2) and nitric acid (NO2) and water (H2O).
RBSE Class 8 Science Chapter 2 Additional Questions and Solutions
Multiple Choice Questions (MCQs)
Choose the correct options for the following:
Question 23: Which is the most abundant metal on earth?
Answer: a) Aluminium
Question 24: Brass is an alloy of —
- Copper and Tin
- Copper and Zinc
- Iron and Zinc
- Silver and Copper
Answer: b) Copper and Zinc
Question 25: Which metal burns in air at a high temperature producing a lot of heat?
Answer: c) Aluminium
Question 26: Non-metals except graphite are __________________ of heat and energy.
Answer: a) Insulators
Question 27: Alloys are _______________________ solid mixtures of metals or of metals and non-metals.
Answer: b) Homogeneous
Question 28: What gas does a metal form while reacting with an acid?
- Carbon dioxide
Answer: c) Hydrogen
Question 29: _________________ have a special metallic lustre.
- None of the above
Answer: b) Metals
Question 30: Which of the following metals has a low melting point of 29.76° C even when kept on the palm of a hand?
Answer: d) Gallium
Question 31: ______________________ are brittle in nature and cannot be stretched into wires or sheets either by beating or hammering.
- All of the above
Answer: c) Non-metals
Question 32: Sodium metal is highly _________________.
Answer: d) Reactive
Question 33: Bronze is an alloy of —
- Copper and Tin
- Copper and Zinc
- Iron and Zinc
- Silver and Copper
Answer: a) Copper and Tin
Question 34: __________________ is used in pesticides, matchsticks, etc.
- Red phosphorous
Answer: c) Red phosphorous
Question 35: __________________ wire is used in electric wires, refrigerators, etc.
Answer: c) Copper
Question 36: What are those elements called which neither fit with metals nor with non-metals?
- None of the above
Answer: b) Metalloids
Question 37: Which of the following metals does not react with steam?
Answer: d) Silver
Question 38: Identify the metal which is the most ductile?
Answer: b) Gold
Question 39: Metals react with acid and give _________________ gas.
- Carbon dioxide
Answer: b) Hydrogen
Very Short Answer Questions
Question 40: What is an inert metal?
Answer: A metal which does not react with water, air or acid is known as an inert metal. Due to this reason, gold or silver never lose their lustre easily.
Question 41: How is the purity of gold measured?
Answer: Purity of gold is measured in Karat. 24K gold is considered the purest form of gold. Anything less than 24K gold has a mix of other metals in it.
Question 42: Why are metals considered as good conductors of electricity?
Answer: Metals are considered as good conductors of electricity because they have free electrons in them.
Question 43: Explain why aluminium is extensively used for cooking purposes?
Answer: Aluminium is often used for cooking purposes as it is a very lightweight metal, which is a good conductor of heat and is resistant to corrosion.
Question 44: Can you define the possible cause for rusting of iron?
Answer: Iron tends to rust because it is caused by oxide formation.
Short Answer Questions
Question 45: What is an alloy?
Answer: An alloy is a homogeneous solid mixture of metals and non-metals or a combination of different metals. A parent metal is mixed with a stranger metal to obtain desired properties in the parent metal. For example, stainless steel, bronze, brass, etc.
Question 46: Why don’t metals which are made into utensils rust?
Answer: Some metals like utensils which are made of stainless steel don’t rust because they are composed of both metals and non-metals in small quantities. Stainless steel is a mix of Chromium and Nickel. Brass is a mixture of Copper and Zinc in fixed quantities so that they do not rust easily.
Question 47: What do you mean by galvanization?
Answer: Galvanization is the process in which a thin layer of zinc is deposited on the surface of iron substances to prevent them from rusting. For example, galvanized construction steel is extensively used in steel furniture, building frameworks of balconies and staircases, etc.
Question 48: Explain the reason why phosphorus is stored in water.
Answer: Phosphorus is considered to be a highly reactive non-metal. When exposed to air, it catches fire easily. Hence, to prevent the contact of phosphorus with oxygen, it is stored in water.
Question 49: Why do silver jewellery loose shimmer and turn black after using for some days when it does not react with air?
Answer: Silver does not react with air but it tends to react with the sulphur particles present in oxygen. This creates a black layer of silver sulphide and the silver jewellery turns black after sometime.
Long Answer Questions
Question 50: What are the uses of metals and non-metals in our daily life?
Answer: Here are some of the uses of metals and non-metals are given as below:
Uses of Metals:
- Metals are used in utensils which are used for cooking purposes.
- Iron and Aluminum sheets are extensively used at roofs of homes in order to prevent it from sun or rain.
- Copper wires are used in electrical instruments such microwaves, radio electric wires, fridge, etc.
- Shiny metals like gold and silver are used for making decorative pieces of art, coins, jewellery, etc.
- Metals like gold and silver are being used for making jewellery.
- Mercury is used in thermometers for measuring the body temperature of human beings.
Uses of Non-metals:
- Sulphur is being used in making medicines, acid and gunpowder.
- Graphite is used in pencils which are meant for writing.
- Red phosphorus is being used in pesticides, matchsticks and crackers.
- Graphite is being used in electrodes.
- Nitrogen is being used in fertilizers to promote the growth of plants.
- Chlorine is extensively used for disinfecting drinking water.
We hope that the above mentioned solutions of RBSE Class 8 Science Chapter 2 Metals and Non-Metals will help students grasp a solid understanding about the different concepts mentioned in the chapter.