NCERT Solutions for Class 10 Science

Chapter 1 – Chemical Reactions and Equations

NCERT Solutions for Class 10 Science Chapter 1 deals with Chemical Reactions. In previous classes, students were introduced to physical and chemical changes. Chemical changes reflect chemical reactions. Chemical reactions are explained with some indicators like change in physical state, change in color, change in temperature and evolution of gas. These are explained with some experimental examples. After this, writing chemical equations is explained. It is a symbolic representation of chemical reactions. Additionally, it is also explained how such equations can be more informative. For example, balancing a chemical equation would indicate that chemical reactions follow the law of conservation of mass.

Other information such as physical states and conditions required for reactions are mentioned. After that different types of chemical reactions are explained. The types of chemical reactions are combination reaction, decomposition reaction, displacement reaction, double decomposition reaction. Exothermic and endothermic reactions are mentioned on the basis of energy. Redox reactions have been explained that are a combination of a reduction reaction and an oxidation reaction. All types of reactions are explained with their respective chemical equations along with suitable examples.

Chapter 2 – Acids, Bases and Salts

Acids and bases are studied in previous classes. Acids are defined as substances that are sour in taste and turn blue litmus red. Examples of acids are citrus fruits, just as bases are defined as substances that are bitter in taste and turn red litmus blue. Examples of alkali are neem, clove, vinegar etc. Here, acid and base are defined chemically. Acids are those substances which produce hydrogen ions H+ after dissolving in water. Hydrogen ion H+ dissolves in water to form hydronium ion H3O+ ion. Examples of acids are sulfuric acid, H2SO4, HCl, HNO3, CH3COOH. Bases are chemically those substances which produce OH- ions in aqueous solution, if not then they are weak acids. Examples are sodium hydroxide, NaOH, potassium hydroxide KOH etc. After that, various chemical and olfactory indicators are discussed; This indicates the presence of acid or base in the solution. The strength of an acid or base depends on its ability to generate H+ or OH- ions respectively. An acid is considered strong if it can be completely dissociated into H+ ions. Bases are said to be strong if they all dissociate in water to form OH- ions. For example, methyl orange is a chemical indicator. It turns red in acidic solution and yellow in alkaline solution. Olfactory indicators are indicators that change odor after exposure to acids and bases. For example, the smell of cloves disappears when exposed to acid.

Acid and base reactions with metals, metal oxides, and metal carbonates are then discussed. Reactions between acids and bases are also discussed. These are known as neutralization reactions. Salt is one of the products of the acid-base reaction. Different types of salts are discussed depending on the strength of the acid or base. Salt can be neutral, acidic or alkaline, depending on the strength of the acid/base used to make the salt. The pH scale indicates whether the solution is acidic or alkaline, neutral. This scale ranges from 0-14. 0 represents a highly acidic solution, 14 represents a highly alkaline solution. 7 is neutral. So, 0-7 is acidic, 7 is neutral, 7-14 is basic solution. The Universal Indicator is a combination of several indicators. It shows different colors at different concentrations of H+ ions in solution. Chloro-alkali process is done with salt solution. Various chemical substances are formed after reactions, directly or indirectly used for various processes. Some such chemical salts are bleaching powder, washing soda, baking soda, plaster of Paris. In this chapter their construction and use has been explained.

Chapter 3 – Metals and Nonmetals

The chapter begins with the physical properties of metals and non-metals. Among the parameters discussed are some of the physical properties, such as melting and boiling points, physical state at room temperature, ductility, ductility, tensile strength, etc. are also discussed. Metals and non-metals are differentiated on the basis of physical properties. But there are also some expectations based on physical qualities. For example, iodine is a non-metal but looks shiny like a metal. Mercury is metal but liquid at room temperature. There are other such exceptions. Therefore, classification of metals and non-metals is based on chemical properties. The chemical reactions of metals with oxygen gas, water, acids and other metal salts are discussed here. The reactions and their positions depend on the reactivity series. The metals at the top of the reactivity series are sodium and potassium. They react strongly. The nature of metallic oxides has been discussed. Generally metal oxides are alkaline in nature. But, some of them like aluminum oxide and zinc oxide can be both acidic and basic and hence they are known as amphoteric oxides.

How such reactions occur is then discussed. Ionic bond formation is discussed. This type of bond formation can be represented in two forms. Electrons are given up by metals and electrons are gained by non-metals. One becomes positively charged and the other becomes negatively charged. They are attracted and a strong relationship is formed. The first is electronic configuration. Bond formation is discussed through the Bohr model. Another method is the Lewis structure or electron-dot structure. Metals and non-metals are written with their symbols and dots. The number of dots indicates the number of outermost electrons. The properties of ionic bonds discussed are based on strong ionic bond formation.

Metal extraction is also taught. Metals are extracted from minerals, their ores. Ores are minerals from which extraction of metals is profitable. The impurities are removed and then processing takes place according to the reaction of the metals. Highly reactive metals are extracted by electrolysis. The middle reactive metals are first converted into oxides and then into metals. Metals lower in the reactivity series like gold, silver, platinum etc. are found in their native state and do not need to be processed. After this the metal is refined which is the second level of purification. It is necessary to protect the extracted metals from corrosion. A lot of money is spent on this. Various methods like oiling, greasing, electroplating, galvanization etc. have been discussed. The second method is alloy. It is the process of mixing metals with other metals or nonmetals. It makes the metal corrosion free and increases strength. Steel metal is an alloy of iron and non-metallic carbon, which is used in construction work. Other such alloys are stainless steel, brass, bronze, duralumin etc.

Chapter 4 – Carbon and its Compounds

Class 10 Science NCERT Solutions Chapter 4 is about Carbon which is a versatile element found in many organic and inorganic compounds. This is because of its tetravalency and catenation which have been discussed. Carbon forms bonds by sharing its electrons with other elements. Such bond formation of elements formed by exchange of electrons is called covalent-bond formation. Covalent bond formation has been explained for compounds made from other covalent bonds such as oxygen gas, nitrogen gas and compounds made from covalent bonds.

Compound formation is explained in both electron-dot/Lewis-dot structure and electronic configuration. The structure of various carbon compounds is explained. For example, organic compounds are formed in straight chains, or branched chains, or cyclic chains. Organic compounds are also classified on the basis of saturated and unsaturated compounds. Saturated compounds are compounds with only single bonds. Unsaturated carbon compounds are compounds with double or triple bonds. Organic compounds are basically carbon-hydrogen chains. Functional groups can be an atom or group of atoms linked by a hydrogen-carbon chain. Some functional groups are alcohol –OH, carboxylic acid –COOH, chlorine, –Cl, –ketone and aldehyde –CHO, cyanide –CN.

The system of naming a large number of atoms is also taught. Some important carbon compounds like ethyl alcohol used to make alcoholic beverages and ethanoic acid used to make vinegar are discussed along with their physical and chemical properties. Soaps and detergents are studied along with their chemical structure and properties. Their differences have also been discussed. Detergent is used for cleaning hard water.

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Chapter 5 – Periodic Classification of Elements

So far 118 known elements have been found. It is better to study each element in a proper manner. For this we have to classify them in an order. If classified in order, we can easily predict some trends in the physical and chemical properties of the elements. Therefore, scientists worked to arrange all the elements in such a way that similar elements could be placed in certain rows and columns. In the year 1817, Johann Wolfgang Dobereiner showed that when the three elements in a triad were written in order of increasing atomic mass; The atomic mass of the middle element was approximately the average of the atomic masses of the other two elements. For example, A, B and C form a triplet, the atomic mass of B is the average of the atomic masses of A and B. But, this method doesn’t work for every element. Only three triads can be detected. In 1866 John Newlands attempted to systematize the elements. Newland’s Octave was another method of classifying elements. In this, when placed in the order of atomic mass, every eighth element will show the properties of the first element. This was similar to musical notes where the first node is the same as the eighth. This also failed because it was not able to work for more than 56 elements.

The second method was adopted by Dmitri Mendeleev. Mendeleev arranged the elements on the basis of their atomic masses. He observed that when elements were arranged in increasing order of their atomic masses, there was a periodic recurrence in their physical and chemical properties. Thus, Mendeleev formulated a periodic law, which states that ‘the properties of elements are periodic functions of their atomic masses’. Mendeleev’s periodic table has vertical columns called ‘groups’ and horizontal rows called ‘periods’. It was much more accurate than previous models. It also had some demerits. Eventually the modern periodical came into existence. Atomic number was considered the criterion for classification. Elements in the same group have the same number of outermost electrons. Elements in the same period have the same number of outermost shells. A certain pattern can be predicted ranging from a particular increase to a decrease. Many such trends have been studied in this chapter.

Chapter 6 – Life Processes

Chapter 6 Life Processes NCERT Solutions are about the various activities performed by living beings to maintain life. Such processes are digestive system, respiratory system, circulatory system etc. It is important to leave all these things. The point is to consume food through the digestive system, oxidation of food which includes the process of respiration, and transportation of food and water which is done through circulation. This chapter starts with the process of nutrition. The process by which an organism takes in food, uses it to obtain energy, growth, repair and maintenance, etc. is nutrition. Other modes of nutrition are autotrophic and heterotrophic nutrition which are discussed in the chapter. Autotrophic nutrition by plants is achieved through photosynthesis. Heterotrophic nutrition is provided by animals. Various types of heterotrophic nutrition have been discussed. Parasitic nutrition, saprotrophic nutrition and holozoic nutrition are different types of heterotrophic nutrition. Cellular nutrition is done by unicellular organisms which has been discussed in this chapter. The next topic is human nutrition. It starts in the mouth which includes salivary glands, tongue and teeth. Food passes through the esophagus into the stomach. Food goes into the stomach. The liver secretes a greenish yellow colored fluid called bile juice. The pancreas is located behind the lower part of the stomach. This pancreas secretes juice which contains many digestive enzymes. All such processes have been discussed in this digestive system.

Next is respiration. The process of respiration includes: (a) Gaseous exchange i.e. breathing: intake of oxygen from the atmosphere and release of CO2. and (b) cellular respiration: the breakdown of simple food to release energy inside the cell. There is discussion of both. The human respiratory system is discussed with special attention. Pharynx, bronchi, lungs, diaphragm are different elements of the human respiratory system. The mechanism of the process involves inhalation and exhalation. Both have been explained. Circulation involves the process of moving food and other materials from one place to another. Blood is pumped through the heart and delivered through veins. So, all of them have been discussed. The various components of blood are discussed – red blood cells and white blood cells. The four chambers of the heart have been discussed.

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Chapter 7 – Control and Coordination Systems

Earlier, we all had this belief that if we see something moving, it is alive. Some of these activities are actually the result of growth, such as in plants. A seed germinates and grows, and we can see the sprout move over the course of a few days, control and coordination are the functions of the nervous system and hormones in our body. Nervous system responses can be classified as reflex actions, voluntary actions, or involuntary actions. The nervous system uses electrical impulses to transmit messages. The nervous system receives information from our senses and acts through our muscles. Chemical coordination is seen in both plants and animals. Hormones produced in one part of the organism move to another part to achieve the desired effect. A feedback mechanism controls the action of hormones.

Chapter 8 – How Do Organisms Reproduce?

Unlike other life processes, reproduction is not necessary to maintain the life of an organism. This process involves the creation of a DNA copy and additional cellular equipment by the cell involved. Different organisms use different methods of reproduction depending on the design of their body such as fragmentation, fission, regeneration, budding, spore formation and vegetative propagation. Sexual reproduction involves two individuals joining together to create a new individual. Sexual reproduction methods allow greater diversity to occur.

Reproduction in flowering plants involves the transfer of pollen grains from the anther to the stigma, which is called pollination and subsequent fertilization. The male reproductive system in humans consists of the testes which produce sperm, the vas deferens, the seminal vesicle, the prostate gland, the urethra, and the penis. The female reproductive system in humans includes the ovaries, fallopian tubes, uterus, and vagina. Sexual reproduction in humans involves the entry of sperm into the vagina of a woman. Fertilization occurs in the fallopian tube.

Chapter 9 – Heredity and Evolution

We have seen that reproductive processes give rise to new individuals that are similar, but subtly different. We have discussed how some amount of variation occurs even during asexual reproduction. Heredity and evolution are related to this phenomenon – the long-term consequences of the accumulation of variations. The laws of inheritance of traits (Mendel’s contributions) set out the process by which traits and characteristics are reliably inherited. The fact of sex determination in a newborn baby has been completely resolved. Evolution can be traced by studying not only living species, but also fossils. Even in intermediate stages, complex organs may evolve due to survival benefits. Changes occurring in non-reproductive tissues due to environmental factors are not heritable, suggesting a variety of traits such as acquired and hereditary. Speciation can occur when variation is combined with geographic isolation. Evolutionary relationships are traced in the classification of organisms. Studies of human evolution indicate that we are all a single species that evolved in Africa and spread around the world in stages.

Chapter 10 – Light: Reflection and Refraction

Light is the source of energy which produces the sensation of vision in humans. The first reflection of light has been discussed in this chapter. Reflection is controlled by its laws. The chapter deals with the laws of reflection. Here we are basically concerned with spherical mirrors. Image formation by spherical mirrors is then discussed. Different types of spherical mirrors, convex and concave are taught. Various terms related to spherical mirror like center of curvature, radius of curvature etc., focus, pole etc. are discussed with ray diagrams. The chapter discusses the use of spherical mirrors. The mirror formula is a way to relate the object distance, image distance, and focal length of the mirror. Magnification is the ratio of the size of the image by the size of the object. It is related to the ratio of image distance to object distance. The distances are determined from the pole of the mirror. The signal convention is taken into account to find the relative distance of the image and object.

Chapter 11 – The Human Eye and the Colorful World

The human eye, its components have been discussed. The process by which the human eye can see objects is discussed. The ability of the eye to focus on both near and distant objects, by adjusting its focal length, is called accommodation of the eye. The minimum distance at which the eye can see objects clearly without strain is called the near point of the eye or the minimum distance of clear vision. For a young adult with normal vision, this is about 25 cm. The visual defects are discussed along with their corrective measures using suitable ray diagrams. Common refractive errors of vision include myopia, hypermetropia, and presbyopia. Myopia (shortsightedness – images of distant objects are focused before the retina) is corrected using a concave lens of appropriate power. Hypermetropia (farsightedness – the image of nearby objects is focused beyond the retina) is corrected using a convex lens of appropriate power. In old age the eye loses its accommodative capacity. The splitting of white light into its component colors is called scattering. Due to scattering of light the color of the sky becomes blue and at the time of sunrise and sunset the color of the sun becomes red.

Chapter 12 – Electricity

Many things around us require electricity. What is electricity? This is a phenomenon related to the flow of charge. The concepts of electric current and electric potential difference (voltage) are taught. The flow of electrons moving through a conductor creates electric current. Conventionally, the direction of current is taken opposite to the direction of flow of electrons. The SI unit of electric current is ampere. We use a cell or battery to move electrons in an electrical circuit. A cell produces a potential difference across its terminals. It is measured in volts (V). Resistance is a property that opposes the flow of electrons in a conductor. It controls the magnitude of the current. The SI unit of resistance is ohm (Ω). Ohm’s law, which establishes the relationship between potential difference and current, is discussed. Ohm’s Law: The potential difference across a resistor is directly proportional to the current flowing through it, provided its temperature remains the same. The concepts of resistance and resistivity are studied. Resistance is the property of any conductor to oppose the flow of electric current. The resistance of a conductor depends directly on its length, inversely on the area of its cross-section, and also on the material of the conductor. The resistance of a conductor with unit length and cross section is defined by the specific resistance. Series and parallel combination of resistors have been discussed. The current in series is the same and the potential difference between the resistors in parallel is the same. The electrical energy dissipated in a resistor is given by W = V × I × t. The unit of power is Watt (W). When 1 A current flows across a potential difference of 1 V, one watt of power is consumed. The commercial unit of electrical energy is the kilowatt hour (kWh). 1 kWh = 3,600,000 J = 3.6 × 106 J.

Chapter 13 – Magnetic Effect of Current

The relationship between magnetism and electricity is discussed in this chapter. First some basics of magnetism along with magnetic field lines are discussed. The compass needle is a tiny magnet. One end of it, which points towards the north, is called the North Pole and the other end, which points towards the south, is called the South Pole. Magnetic field lines are used to represent magnetic fields. The field line is the path along which an imaginary free north pole moves. The direction of the magnetic field at a point is given by the direction that a north pole placed at that point would take. Thicker magnetic field lines indicate greater magnetic field strength. After that, the magnetic field produced due to a current carrying conductor has been discussed. There is a magnetic field associated with a metal wire carrying an electric current whose direction is given by the right hand thumb rule. An electromagnet consists of a core of soft iron surrounded by a coil of insulated copper wire. When an electric current carrying conductor is placed in a magnetic field, a force is exerted on it. The events related to this have been explained.

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If the direction of the field and the direction of the current are mutually perpendicular to each other, then the force on the conductor will be perpendicular to both and is given by Fleming’s left-hand rule. This is the basis of an electric motor. An electric motor is a device that converts electrical energy into mechanical energy. The working and construction of electric motor was discussed. Generation of electricity by magnets has been discussed. The phenomenon of electromagnetic induction is the production of induced current in a coil placed in a region where the magnetic field changes with time. The magnetic field may change due to the relative motion between the coil and a magnet placed near the coil. If a coil is placed near a conductor carrying an electric current, the magnetic field may change either due to a change in the current flowing through the conductor or due to the relative motion between the coil and the conductor. The direction of the induced current is given by Fleming’s right hand rule. A generator converts mechanical energy into electrical energy. It works on the basis of electromagnetic induction.

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Two types of generators are discussed. A DC generator produces direct current in the form of a cell. AC generators produce alternating current whose direction changes over a period of time. Domestic circuiting is discussed. In our homes we get AC electric power of 220 V with a frequency of 50 Hz. Various aspects have been discussed. The concepts of live wire, neutral wire and earth wire are discussed. 220V is maintained between the live wire which is red insulated and the neutral wire which is black insulated. Earth wire, insulated green which provides a path for leakage of current.

Chapter 14 – Sources of Energy

Our energy requirements increase with our standard of living. To meet our energy requirements, we try to improve the efficiency of energy use and also try to exploit new sources of energy. This chapter is about different sources of energy. Three types of sources of energy have been discussed. The first is traditional sources of energy. These are the sources of energy that we have been using for years. This includes fossil fuel, thermal power plants and hydroelectric power plants. These advantages and disadvantages have been discussed.

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After that, energy sources traditionally used, but improved due to technology, are discussed. For example, the cow dung used initially had low calorific value and its combustion caused a lot of pollution. But, with the help of technology, it can be converted into bio-gas, which is an efficient and pollution-free fuel. Similarly, with the help of technology, wind energy can be harnessed by building a wind farm over a large area and installing many windmills. Coal obtained from wood is a better fuel than wood. All these things are discussed. The third category is non-conventional sources of energy. In this category we have energy sources like solar power, in which energy is generated through solar cells and solar panels, or solar cookers. Energy from the ocean can be generated through waves, tides or temperature differences between the upper and lower levels of the ocean. Energy can also be obtained from the Earth’s crust, known as geothermal energy. Nuclear energy can be generated by controlled nuclear fission reactions. Nuclear fusion reactions produce more energy than fission but are difficult to control. All such sources of energy have been discussed with their advantages and disadvantages.

Chapter 15 – Our Environment

Different components of an ecosystem depend on each other. Producers make the energy from sunlight available to the rest of the ecosystem. As we move from one trophic level to another, energy is lost, limiting the number of trophic levels in a food chain. This concept of food chain and food web is discussed along with the concept of biological magnification. This is the process of accumulation of pesticides or other harmful chemicals. The impact of human activities is discussed in this chapter. The use of chemicals like CFCs has endangered the ozone layer. Since the ozone layer protects against ultraviolet radiation coming from the Sun, it can cause harm to the environment. Different types of waste materials have been discussed. The waste we generate can be biodegradable or non-biodegradable. The disposal of waste generated by us is causing serious environmental problems. Therefore, there is a need for a proper waste management system.

Chapter 16 – Sustainable Management of Resources

In class 9, we have been taught about some natural resources like soil, air and water and how different components cycle again and again in nature. In this chapter, we’ll take a look at some of our resources and how we’re using them. This chapter introduces us to the concern regarding inappropriate use of natural resources. The example of Ganga Action Plan teaches how qualitative and quantitative analysis helps in understanding the need for management of natural resources. Perhaps we should also think about how we should use our resources so as to conserve resources and preserve our environment. The 3R method has been discussed. We will look at our natural resources such as forests, wildlife, water, coal and petroleum and see what issues are at stake in deciding how to manage these resources for sustainable development. Various methods have been discussed to utilize resources in such a way that natural resources reach every section of the society. Additionally, environmental impact must also be considered. Additionally, the limited stock of such resources must also be considered.

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NCERT Solutions for Class 9 Science

S. No.	Unit Name	Weightage
1	Chemical Substances – Nature & Behaviour	25
2	World of living	23
3	Natural Phenomena	12
4	Effects of Current	13
5	Natural Resources	07
Total Marks		80
20 Marks will be internal assessment

As you will see the exam pattern, CBSE is focusing more on objective type questions, so we have prepared MCQs and also provided VSAQs so that students can prepare accordingly. Since the answers are prepared by experienced experts of StudyRankers, you can trust the answers and use it to improve your scores in exams.